The Role of Capacitor Replacement in HVAC System Repairs

blower fan replacement

Capacitors play an integral role in the functionality of air conditioning units, serving as a crucial component within HVAC systems. Their primary purpose is to store and release electrical energy, which is vital for the initiation and continuous operation of the compressor and fan motors. Without capacitors, many HVAC systems would struggle to start up or run efficiently, leading to potential system failures and increased energy consumption.


In air conditioning units, capacitors are typically found in two forms: start capacitors and run capacitors. Start capacitors provide the necessary jolt of electricity needed to initiate a motor's operation, ensuring that compressors have enough torque to begin their cycles. On the other hand, run capacitors offer a steady stream of power that maintains motor operation after it has started. Seasonal weather changes can impact performance, making Residential air conditioner repair addressing minor issues now can prevent major repairs later.. These components work together to ensure that air conditioners function smoothly and effectively.


However, like all mechanical components, capacitors can wear out over time due to various factors such as temperature fluctuations, voltage spikes, or simple aging. A failing capacitor can lead to inefficient cooling performance or even prevent the unit from starting altogether. This is where capacitor replacement becomes a significant aspect of HVAC system repairs.


Replacing a faulty capacitor is often one of the most cost-effective solutions for restoring an air conditioning unit's performance. Not only does this repair ensure that motors receive adequate electrical support to function properly, but it also helps maintain optimal energy efficiency. When left unchecked, defective capacitors can cause undue stress on other parts of the system, potentially leading to more severe damage and costly repairs down the line.


Moreover, regular inspection and timely replacement of worn-out capacitors can prolong the lifespan of an air conditioning unit. It minimizes downtime during peak usage periods-such as hot summer months when reliable cooling is essential-and contributes significantly towards maintaining indoor comfort levels.


In conclusion, while often overlooked by homeowners until problems arise, capacitors are pivotal components within HVAC systems that require attention during routine maintenance checks. Their replacement not only addresses immediate operational issues but also supports long-term efficiency and reliability in air conditioning units. As such, understanding their role and ensuring they are in good working condition should be a priority for anyone invested in maintaining their home's climate control systems efficiently.

Overview of Capacitors in Air Conditioning Units

Importance of Capacitors in HVAC Functionality

Capacitors play a pivotal role in the functionality of HVAC systems, acting as unsung heroes within these complex machines. Their importance cannot be overstated, as they are crucial for ensuring that heating, ventilation, and air conditioning units operate efficiently and reliably. In this context, understanding the significance of capacitors and their replacement is essential for maintaining the health and longevity of HVAC systems.


At its core, a capacitor stores electrical energy temporarily and releases it when needed. This function is vital in HVAC systems because it helps to regulate voltage and stabilize power supply to the motors that drive fans, compressors, and other critical components. Without capacitors, these motors would struggle to start or run at optimal performance levels, leading to inefficiencies or even system failures.


In particular, start capacitors provide an extra jolt of energy required to initiate motor operation. Once the motor reaches a certain speed, run capacitors then take over by maintaining a steady flow of current to keep the motor running smoothly. Thus, both types of capacitors ensure that HVAC systems can respond quickly during startup while maintaining consistent performance during operation.


Over time, however, capacitors can degrade due to factors such as heat exposure or electrical surges. When this happens, their ability to store and discharge electricity diminishes significantly. This degradation often manifests through symptoms like frequent cycling on and off of the unit or unusual noises emanating from the system-clear indicators that it might be time for capacitor replacement.


The role of capacitor replacement in HVAC system repairs is therefore crucial. Regular inspection and timely replacement can prevent minor issues from escalating into major problems. A faulty capacitor not only jeopardizes system efficiency but also places additional strain on other components like compressors and fans. By replacing worn-out capacitors promptly, technicians can restore balance within the system's electrical circuitry and potentially extend its overall lifespan.


Moreover, investing in high-quality replacement capacitors pays dividends in terms of enhanced reliability and energy efficiency. Modern advancements have led to more robust designs capable of withstanding harsh conditions typical in HVAC environments. These improvements further underscore why keeping tabs on capacitor health should be an integral part of any preventative maintenance strategy.


In conclusion, while capacitors may seem like small components within an expansive HVAC system landscape, their impact is profound. They facilitate smooth operation by managing electrical demands effectively-a task that becomes critically important as HVAC systems work tirelessly across seasons to maintain indoor comfort levels. Through regular assessment and timely replacement when needed, homeowners and facility managers alike can ensure their HVAC systems remain reliable stalwarts against whatever weather challenges lie ahead.

Signs of a Failing Capacitor in AC Systems

In the intricate world of HVAC systems, capacitors play a crucial role in ensuring efficient operation and performance. Much like the heart in a human body, these small yet mighty components store and release energy to power the system's motors and compressors. However, over time, capacitors can deteriorate and start exhibiting signs of failure, which can significantly affect the overall functionality of an air conditioning unit.


Identifying the signs of a failing capacitor early on is essential for preventing more serious issues within an HVAC system.

The Role of Capacitor Replacement in HVAC System Repairs - airflow balancing

  1. blower fan replacement
  2. boiler maintenance
  3. airflow balancing
One of the most noticeable symptoms is a decrease in cooling efficiency. If an air conditioner struggles to maintain the desired temperature or takes longer than usual to cool a room, it could indicate that the capacitor is losing its ability to supply adequate power to the compressor or fan motor.


Additionally, unusual noises coming from the AC unit are another common indicator of capacitor problems. A humming or clicking sound when the system is attempting to start up often suggests that the capacitor is struggling to hold its charge, leading to difficulties in powering up essential components. This sound should not be ignored as it can precede more severe malfunctions.


Frequent cycling on and off of the air conditioning unit is also a red flag for potential capacitor failure. When a capacitor cannot maintain consistent power delivery, it causes erratic operation cycles that put unnecessary strain on other parts of the system. This not only reduces efficiency but also increases wear and tear on components such as compressors and motors.


In some cases, visual inspection may reveal physical signs of damage to the capacitor itself. Bulging or leaking capacitors indicate internal failures due to overheating or electrical stress. Such visible damage warrants immediate replacement before it leads to complete system breakdowns.


The role of timely capacitor replacement cannot be overstated in HVAC repairs. Addressing these signs promptly by replacing failing capacitors ensures smoother operation and prolongs the lifespan of other critical components within an AC system. Moreover, regular maintenance checks by qualified technicians help identify potential issues before they escalate into costly repairs.


By understanding these warning signals and prioritizing proactive maintenance strategies like capacitor replacement, homeowners can ensure their HVAC systems operate efficiently during peak demand periods while avoiding unexpected breakdowns. Ultimately, recognizing and addressing capacitor issues early contributes significantly to maintaining optimal comfort levels in living spaces throughout changing seasons.

Signs of a Failing Capacitor in AC Systems
The Impact of Faulty Capacitors on Air Conditioning Performance

The Impact of Faulty Capacitors on Air Conditioning Performance

Air conditioning systems are integral to maintaining comfort in both residential and commercial spaces, especially during the sweltering heat of summer. However, the performance of these systems can be significantly compromised by faulty components, with capacitors being one of the most critical yet often overlooked parts. Understanding the impact of faulty capacitors on air conditioning performance is crucial for both homeowners and HVAC professionals who aim to ensure optimal functioning and longevity of these systems.


Capacitors play a vital role in the operation of an air conditioning unit. They store and release electrical energy, providing the necessary jolt to start the compressor and fan motors. Essentially, they act as a battery that helps power the motor when it needs an extra boost to initiate cooling operations. When a capacitor becomes faulty or fails altogether, it can lead to a myriad of problems that adversely affect air conditioning performance.


One immediate impact of a faulty capacitor is difficulty starting up the system. Known as "hard starting," this issue occurs when the capacitor cannot provide sufficient power for startup, causing delays or failure in motor function. This not only results in discomfort due to inadequate cooling but also places additional strain on other components like compressors and fans, leading to premature wear and tear.


Furthermore, if a capacitor is malfunctioning, it can cause erratic operation or frequent cycling on and off. This inconsistency not only reduces efficiency but also increases energy consumption as the system struggles to maintain desired temperature levels. As energy bills rise, so does frustration among users who find themselves paying more for less effective cooling.


Regular maintenance checks can help diagnose capacitor issues before they escalate into bigger problems. During such inspections, HVAC technicians assess whether capacitors are holding their charge properly or if there are signs of swelling or leakage—common indicators that replacement might be necessary.


Replacing faulty capacitors should be seen as an essential part of HVAC system repairs rather than a mere optional fix. By ensuring that capacitors are functioning correctly, homeowners can prevent cascading failures within their air conditioning units that result from overburdened motors or damaged compressors.


Moreover, timely replacement of bad capacitors contributes significantly towards prolonging the lifespan of an entire HVAC system. It reduces unnecessary stress on other components while restoring efficiency back to its original state—saving money in repair costs down the line while enhancing overall reliability during peak usage periods.


In conclusion, recognizing how pivotal capacitors are within air conditioning systems underscores why addressing any faults promptly is indispensable for maintaining top-notch performance. Homeowners should prioritize regular maintenance schedules with professional inspections focused specifically on component integrity—including those all-important yet oft-overlooked capacitors—to ensure uninterrupted comfort throughout hot weather months without incurring exorbitant utility expenses or costly repairs later on through avoidable neglect today.

Steps for Diagnosing a Bad Capacitor in HVAC Repairs

The role of capacitors in HVAC systems is pivotal, yet often overlooked until problems arise. These small but essential components store and release electrical energy, providing the necessary boost to start and run the motors efficiently. When a capacitor fails, it can lead to various issues, from inefficient system performance to complete breakdowns. Diagnosing a bad capacitor is a critical skill for anyone involved in HVAC repairs.


Identifying a faulty capacitor involves a systematic approach that begins with understanding the symptoms of failure. Common signs include the HVAC system not starting, taking longer than usual to start, or shutting off unexpectedly. Additionally, you might hear unusual noises like humming or notice that the air conditioner isn't blowing cold air as effectively as before.


Once these symptoms are identified, the next step involves ensuring safety before proceeding with any diagnosis. Turn off all power to the HVAC unit at the breaker box to prevent any electrical hazards. Safety goggles and gloves are recommended for added protection against unexpected discharges.


With safety measures in place, visually inspect the capacitor for any physical signs of damage such as bulging, leaking fluids, or rust on terminals. If any of these symptoms are present, it's likely that the capacitor needs replacement.


For a more definitive diagnosis, use a multimeter set to capacitance mode. First, discharge the capacitor by shorting its terminals with an insulated screwdriver-this ensures no residual charge remains. Then disconnect it from the circuit following manufacturer guidelines and connect it to your multimeter probes. Compare the reading with specifications indicated on the capacitor's label; significant deviations suggest malfunction.


If diagnostic tests confirm that the capacitor is faulty, replacing it becomes imperative for restoring HVAC functionality. Using an incorrect type or rating can cause further damage-thus consulting equipment manuals or professional advice when selecting replacements is crucial.




The Role of Capacitor Replacement in HVAC System Repairs - boiler maintenance

  1. residential HVAC systems
  2. indoor air quality
  3. geothermal heating and cooling

In conclusion, diagnosing and addressing issues with capacitors in HVAC systems require attentiveness and precision due to their critical role in system operation. By learning how to accurately identify signs of failure and safely conduct diagnostic procedures using tools like multimeters, technicians can ensure timely repairs that maintain efficiency and longevity of heating and cooling systems in homes and commercial spaces alike.

The Process and Benefits of Replacing a Capacitor
The Process and Benefits of Replacing a Capacitor

In the realm of HVAC (Heating, Ventilation, and Air Conditioning) systems, capacitors play a pivotal role in ensuring efficient operation. These components are crucial for starting the motors that drive compressors, fans, and blowers. However, like any mechanical component, capacitors can degrade over time or fail unexpectedly. Understanding the process and benefits of replacing a capacitor is essential for maintaining optimal HVAC performance and avoiding costly repairs.


Capacitors store electrical energy and release it when needed to provide a jolt that starts the motor in an HVAC system. There are primarily two types: start capacitors and run capacitors. Start capacitors provide the necessary boost to start up a motor, while run capacitors maintain a consistent electrical charge during operation. A failing capacitor can lead to inefficient operation or even prevent the system from running altogether.


The process of replacing a capacitor begins with identifying the signs of failure. Symptoms such as inconsistent cooling or heating, unusual noises from the unit, or frequent system shutdowns often indicate a faulty capacitor. Once diagnosed, it's crucial to ensure safety by disconnecting power to the unit before proceeding with replacement.


Removing a faulty capacitor involves detaching it from its mount and disconnecting its wiring connections.

The Role of Capacitor Replacement in HVAC System Repairs - blower fan replacement

  1. HVAC installation
  2. refrigeration repair
  3. heat exchanger inspection
It's important to note the specifications on the old capacitor—such as voltage rating and capacitance—before purchasing a new one to ensure compatibility with your HVAC system. Installing the new capacitor involves reversing these steps: connecting wires as per original configurations and securing it firmly in place.


Replacing a faulty capacitor offers several benefits for an HVAC system. Firstly, it restores efficient operation by providing motors with adequate power during startup and sustained operation phases. This not only enhances performance but also extends the lifespan of other components within the unit by reducing undue stress caused by insufficient power supply.


Moreover, timely replacement helps in maintaining energy efficiency. A struggling motor consumes more electricity than necessary due to insufficient initial power supply from a failing capacitor; thus increasing utility bills significantly over time without delivering desired comfort levels indoors.


Additionally, proactive maintenance through regular inspection can prevent unexpected breakdowns that could result in uncomfortable indoor environments during extreme weather conditions—not to mention expensive emergency repair costs associated with sudden failures.


In conclusion, understanding how capacitors function within an HVAC system underscores their importance in overall operational efficacy—and why timely replacement is beneficial when they show signs of wear or failure symptoms emerge unexpectedly mid-season! By ensuring proper functioning via routine checks or prompt replacements where necessary—you safeguard not just your investment but also ensure uninterrupted comfort throughout seasons ahead while keeping energy consumption optimized efficiently every step along way forward!

Preventive Maintenance Tips to Extend Capacitor Life

Capacitors play a pivotal role in the efficient functioning of HVAC systems, often serving as the heartbeat that keeps these systems running smoothly. As critical components responsible for storing and releasing electrical energy, capacitors aid in starting motors and maintaining power supply consistency. However, like all mechanical components, capacitors are subject to wear and tear over time. Thus, preventive maintenance becomes essential not only to prolong their lifespan but also to ensure the overall reliability of HVAC systems.


Preventive maintenance involves a series of proactive measures aimed at identifying potential issues before they lead to system failures. For capacitors within HVAC systems, this approach can significantly extend their life expectancy and enhance performance efficiency. One fundamental tip is regular inspection. By periodically checking capacitors for signs of physical damage such as bulging or leakage, technicians can detect potential failures early on. Catching these signs early allows for timely interventions that prevent unexpected breakdowns.


Another vital aspect of preventive maintenance is cleanliness. Dust and debris accumulation around capacitors can lead to overheating-a common cause of capacitor failure. Ensuring that the HVAC environment remains clean minimizes heat buildup and enhances airflow around the components, which helps maintain optimal operating temperatures.


Voltage monitoring also plays a crucial role in extending capacitor life. Capacitors are designed to operate within specific voltage ranges; consistently exposing them to voltages beyond those limits can shorten their lifespan dramatically. Technicians should regularly measure the voltage levels across capacitors to ensure they remain within the specified range, making adjustments as necessary.


In addition to these direct maintenance tips, it's important not to overlook the broader context in which capacitors operate. For instance, maintaining proper temperature control throughout the entire HVAC system reduces strain on all its parts-including capacitors-thereby promoting longevity. Similarly, ensuring other components such as fans and coils are working efficiently prevents unnecessary stress on capacitors.


Despite best efforts at preventive maintenance, capacitor replacement will eventually become necessary due to natural degradation over time. Recognizing when a capacitor has reached the end of its useful life is critical for avoiding unplanned downtime and costly repairs. Establishing a schedule for routine replacements based on manufacturer recommendations or historical performance data ensures that replacements occur before failure becomes imminent.


In conclusion, preventive maintenance serves as an invaluable strategy in extending capacitor life within HVAC systems while simultaneously enhancing operational reliability and efficiency. Regular inspections, cleanliness practices, voltage monitoring, and contextual awareness together create a comprehensive approach that safeguards against premature failures and contributes positively towards sustainable system operation. By investing time and effort into these proactive measures today, we pave the way for more reliable HVAC performance tomorrow-a testament to foresight marrying technology with prudent care practices.

Preventive Maintenance Tips to Extend Capacitor Life
Geothermal heating

Geothermal heating is the direct use of geothermal energy for some heating applications. Humans have taken advantage of geothermal heat this way since the Paleolithic era. Approximately seventy countries made direct use of a total of 270 PJ of geothermal heating in 2004. As of 2007, 28 GW of geothermal heating capacity is installed around the world, satisfying 0.07% of global primary energy consumption.[1] Thermal efficiency is high since no energy conversion is needed, but capacity factors tend to be low (around 20%) since the heat is mostly needed in the winter.

Geothermal energy originates from the heat retained within the Earth since the original formation of the planet, from radioactive decay of minerals, and from solar energy absorbed at the surface.[2] Most high temperature geothermal heat is harvested in regions close to tectonic plate boundaries where volcanic activity rises close to the surface of the Earth. In these areas, ground and groundwater can be found with temperatures higher than the target temperature of the application. However, even cold ground contains heat. Below 6 metres (20 ft), the undisturbed ground temperature is consistently at the mean annual air temperature,[3] and this heat can be extracted with a ground source heat pump.

Applications

[edit]
Top countries using the most geothermal heating in 2005[4]
Country Production
PJ/yr
Capacity
GW
Capacity
factor
Dominant
applications
China 45.38 3.69 39% bathing
Sweden 43.2 4.2 33% heat pumps
USA 31.24 7.82 13% heat pumps
Turkey 24.84 1.5 53% district heating
Iceland 24.5 1.84 42% district heating
Japan 10.3 0.82 40% bathing (onsens)
Hungary 7.94 0.69 36% spas/greenhouses
Italy 7.55 0.61 39% spas/space heating
New Zealand 7.09 0.31 73% industrial uses
63 others 71 6.8    
Total 273 28 31% space heating
Direct use of geothermal heat by category in 2015 as adapted from John W. Lund [5]
Category GWh/year
Geothermal heat pumps 90,293
Bathing and swimming 33,164
Space heating 24,508
Greenhouse heating 7,407
Aquaculture pond heating 3,322
Industrial uses 2,904
Cooling/snow melting 722
Agriculture drying 564
Others 403
Total 163,287

There are a wide variety of applications for cheap geothermal heat including heating of houses, greenhouses, bathing and swimming or industrial uses. Most applications use geothermal in the form of hot fluids between 50 °C (122 °F) and 150 °C (302 °F). The suitable temperature varies for the different applications. For direct use of geothermal heat, the temperature range for the agricultural sector lies between 25 °C (77 °F) and 90 °C (194 °F), for space heating lies between 50 °C (122 °F) to 100 °C (212 °F).[4] Heat pipes extend the temperature range down to 5 °C (41 °F) as they extract and "amplify" the heat. Geothermal heat exceeding 150 °C (302 °F) is typically used for geothermal power generation.[6]

In 2004 more than half of direct geothermal heat was used for space heating, and a third was used for spas.[1] The remainder was used for a variety of industrial processes, desalination, domestic hot water, and agricultural applications. The cities of Reykjavík and Akureyri pipe hot water from geothermal plants under roads and pavements to melt snow. Geothermal desalination has been demonstrated.

Geothermal systems tend to benefit from economies of scale, so space heating power is often distributed to multiple buildings, sometimes whole communities. This technique, long practiced throughout the world in locations such as Reykjavík, Iceland;[7] Boise, Idaho;[8] and Klamath Falls, Oregon;[9] is known as district heating.[10]

In Europe alone 280 geothermal district heating plants were in operation in 2016 according to the European Geothermal Energy Council (EGEC) with a total capacity of approximately 4.9 GWth.[11]

Extraction

[edit]

Some parts of the world, including substantial portions of the western USA, are underlain by relatively shallow geothermal resources.[12] Similar conditions exist in Iceland, parts of Japan, and other geothermal hot spots around the world. In these areas, water or steam may be captured from natural hot springs and piped directly into radiators or heat exchangers. Alternatively, the heat may come from waste heat supplied by co-generation from a geothermal electrical plant or from deep wells into hot aquifers. Direct geothermal heating is far more efficient than geothermal electricity generation and has less demanding temperature requirements, so it is viable over a large geographical range. If the shallow ground is hot but dry, air or water may be circulated through earth tubes or downhole heat exchangers which act as heat exchangers with the ground.

Steam under pressure from deep geothermal resources is also used to generate electricity from geothermal power. The Iceland Deep Drilling Project struck a pocket of magma at 2,100m. A cemented steelcase was constructed in the hole with a perforation at the bottom close to the magma. The high temperatures and pressure of the magma steam were used to generate 36MW of electricity, making IDDP-1 the world's first magma-enhanced geothermal system.[13]

In areas where the shallow ground is too cold to provide comfort directly, it is still warmer than the winter air. The thermal inertia of the shallow ground retains solar energy accumulated in the summertime, and seasonal variations in ground temperature disappear completely below 10m of depth. That heat can be extracted with a geothermal heat pump more efficiently than it can be generated by conventional furnaces.[10] Geothermal heat pumps are economically viable essentially anywhere in the world.

In theory, geothermal energy (usually cooling) can also be extracted from existing infrastructure, such as municipal water pipes.[14]

Ground-source heat pumps

[edit]

In regions without any high temperature geothermal resources, a ground-source heat pump (GSHP) can provide space heating and space cooling. Like a refrigerator or air conditioner, these systems use a heat pump to force the transfer of heat from the ground to the building. Heat can be extracted from any source, no matter how cold, but a warmer source allows higher efficiency. A ground-source heat pump uses the shallow ground or ground water (typically starting at 10–12 °C or 50–54 °F) as a source of heat, thus taking advantage of its seasonally moderate temperatures.[15] In contrast, an air source heat pump draws heat from the air (colder outside air) and thus requires more energy.

GSHPs circulate a carrier fluid (usually a mixture of water and small amounts of antifreeze) through closed pipe loops buried in the ground. Single-home systems can be "vertical loop field" systems with bore holes 50–400 feet (15–120 m) deep or,[16] if adequate land is available for extensive trenches, a "horizontal loop field" is installed approximately six feet subsurface. As the fluid circulates underground it absorbs heat from the ground and, on its return, the warmed fluid passes through the heat pump which uses electricity to extract heat from the fluid. The re-chilled fluid is sent back into the ground thus continuing the cycle. The heat extracted and that generated by the heat pump appliance as a byproduct is used to heat the house. The addition of the ground heating loop in the energy equation means that significantly more heat can be transferred to a building than if electricity alone had been used directly for heating.

Switching the direction of heat flow, the same system can be used to circulate the cooled water through the house for cooling in the summer months. The heat is exhausted to the relatively cooler ground (or groundwater) rather than delivering it to the hot outside air as an air conditioner does. As a result, the heat is pumped across a larger temperature difference and this leads to higher efficiency and lower energy use.[15]

This technology makes ground source heating economically viable in any geographical location. In 2004, an estimated million ground-source heat pumps with a total capacity of 15 GW extracted 88 PJ of heat energy for space heating. Global ground-source heat pump capacity is growing by 10% annually.[1]

History

[edit]
The oldest known pool fed by a hot spring, built in the Qin dynasty in the 3rd century BC

Hot springs have been used for bathing at least since Paleolithic times.[17] The oldest known spa is a stone pool on China's Mount Li built in the Qin dynasty in the 3rd century BC, at the same site where the Huaqing Chi palace was later built. Geothermal energy supplied channeled district heating for baths and houses in Pompeii around 0 AD.[18] In the first century AD, Romans conquered Aquae Sulis in England and used the hot springs there to feed public baths and underfloor heating.[19] The admission fees for these baths probably represents the first commercial use of geothermal power. A 1,000-year-old hot tub has been located in Iceland, where it was built by one of the island's original settlers.[20] The world's oldest working geothermal district heating system in Chaudes-Aigues, France, has been operating since the 14th century.[4] The earliest industrial exploitation began in 1827 with the use of geyser steam to extract boric acid from volcanic mud in Larderello, Italy.

In 1892, America's first district heating system in Boise, Idaho, was powered directly by geothermal energy, and was soon copied in Klamath Falls, Oregon in 1900. A deep geothermal well was used to heat greenhouses in Boise in 1926, and geysers were used to heat greenhouses in Iceland and Tuscany at about the same time.[21] Charlie Lieb developed the first downhole heat exchanger in 1930 to heat his house. Steam and hot water from the geysers began to be used to heat homes in Iceland in 1943.

By this time, Lord Kelvin had already invented the heat pump in 1852, and Heinrich Zoelly had patented the idea of using it to draw heat from the ground in 1912.[22] But it was not until the late 1940s that the geothermal heat pump was successfully implemented. The earliest one was probably Robert C. Webber's home-made 2.2 kW direct-exchange system, but sources disagree as to the exact timeline of his invention.[22] J. Donald Kroeker designed the first commercial geothermal heat pump to heat the Commonwealth Building (Portland, Oregon) and demonstrated it in 1946.[23][24] Professor Carl Nielsen of Ohio State University built the first residential open loop version in his home in 1948.[25] The technology became popular in Sweden as a result of the 1973 oil crisis, and has been growing slowly in worldwide acceptance since then. The 1979 development of polybutylene pipe greatly augmented the heat pump's economic viability.[23] Since 2000, a compelling body of research has been dedicated to numerically evidence the advantages and efficiency of using CO2, alternative to water, as heat transmission fluid for geothermal energy recovery from enhanced geothermal systems (EGS) where the permeability of the underground source is enhanced by hydrofracturing.[26][27] As of 2004, there are over one million geothermal heat pumps installed worldwide providing 12 GW of thermal capacity.[28] Each year, about 80,000 units are installed in the US and 27,000 in Sweden.[28]

Economics

[edit]
Geothermal drill machine

Geothermal energy is a type of renewable energy that encourages conservation of natural resources. According to the US Environmental Protection Agency, geo-exchange systems save homeowners 30–70 percent in heating costs, and 20–50 percent in cooling costs, compared to conventional systems.[29] Geo-exchange systems also save money because they require much less maintenance. In addition to being highly reliable they are built to last for decades.

Some utilities, such as Kansas City Power and Light, offer special, lower winter rates for geothermal customers, offering even more savings.[15]

Geothermal drilling risks

[edit]
Cracks at the historic Town Hall of Staufen im Breisgau presumed due to damage from geothermal drilling

In geothermal heating projects the underground is penetrated by trenches or drillholes. As with all underground work, projects may cause problems if the geology of the area is poorly understood.

In the spring of 2007 an exploratory geothermal drilling operation was conducted to provide geothermal heat to the town hall of Staufen im Breisgau. After initially sinking a few millimeters, a process called subsidence,[30] the city center has started to rise gradually[31] causing considerable damage to buildings in the city center, affecting numerous historic houses including the town hall. It is hypothesized that the drilling perforated an anhydrite layer bringing high-pressure groundwater to come into contact with the anhydrite, which then began to expand. Currently no end to the rising process is in sight.[32][33][34] Data from the TerraSAR-X radar satellite before and after the changes confirmed the localised nature of the situation:

A geochemical process called anhydrite swelling has been confirmed as the cause of these uplifts. This is a transformation of the mineral anhydrite (anhydrous calcium sulphate) into gypsum (hydrous calcium sulphate). A pre-condition for this transformation is that the anhydrite is in contact with water, which is then stored in its crystalline structure.[35] There are other sources of potential risks, i.e.: cave enlargement or worsening of stability conditions, quality or quantity degradation of groundwater resources, Specific hazard worsening in the case of landslide-prone areas, worsening of rocky mechanical characteristics, soil and water pollution (i.e. due to antifreeze additives or polluting constructive and boring material).[36] The design defined on the base of site-specific geological, hydrogeological and environmental knowledge prevent all these potential risks.

See also

[edit]

References

[edit]
  1. ^ a b c Fridleifsson, Ingvar B.; Bertani, Ruggero; Huenges, Ernst; Lund, John W.; Ragnarsson, Arni; Rybach, Ladislaus (2008-02-11). "The possible role and contribution of geothermal energy to the mitigation of climate change" (PDF). In O. Hohmeyer; T. Trittin (eds.). Proceedings of the IPCC Scoping Meeting on Renewable Energy Sources. Luebeck, Germany. pp. 59–80. Archived from the original (PDF) on 2017-08-08.
  2. ^ Heat Pumps, Energy Management and Conservation Handbook, 2008, pp. 9–3
  3. ^ Mean Annual Air Temperature
  4. ^ a b c Lund, John W. (June 2007), "Characteristics, Development and utilization of geothermal resources" (PDF), Geo-Heat Centre Quarterly Bulletin, vol. 28, no. 2, Klamath Falls, Oregon: Oregon Institute of Technology, pp. 1–9, ISSN 0276-1084, archived from the original (PDF) on 2010-06-17, retrieved 2009-04-16
  5. ^ Lund, John W. (2015-06-05). "Geothermal Resources Worldwide, Direct Heat Utilization of". Encyclopedia of Sustainability and Technology: 1–29. doi:10.1007/978-1-4939-2493-6_305-3. ISBN 978-1-4939-2493-6.
  6. ^ Hanania, Jordan; Sheardown, Ashley; Stenhouse, Kailyn; Donev, Jason. "Geothermal district heating". Energy education by Prof. Jason Donev and students, University of Calgary. Retrieved 2020-09-18.
  7. ^ "History of the utilization of geothermal sources of energy in Iceland". University of Rochester. Archived from the original on 2012-02-06.
  8. ^ "District Heating Systems in Idaho". Idaho Department of Water Resources. Archived from the original on 2007-01-21.
  9. ^ Brown, Brian.Klamath Falls Geothermal District Heating Systems Archived 2008-01-19 at the Wayback Machine
  10. ^ a b "Geothermal Basics Overview". Office of Energy Efficiency and Renewable Energy. Archived from the original on 2008-10-04. Retrieved 2008-10-01.
  11. ^ "EGEC Geothermal Market Report 2016 Key Findings (Sixth Edition, May 2017)" (PDF). www.egec.org. EGEC - European Geothermal Energy Council. 2017-12-13. p. 9.
  12. ^ What is Geothermal? Archived October 5, 2013, at the Wayback Machine
  13. ^ Wilfred Allan Elders, Guðmundur Ómar Friðleifsson and Bjarni Pálsson (2014). Geothermics Magazine, Vol. 49 (January 2014). Elsevier Ltd.
  14. ^ Tadayon, Saied; Tadayon, Bijan; Martin, David (2012-10-11). "Patent US20120255706 - Heat Exchange Using Underground Water System".
  15. ^ a b c Goswami, Yogi D., Kreith, Frank, Johnson, Katherine (2008), p. 9-4.
  16. ^ "Geothermal Heating and Cooling Systems". Well Management. Minnesota Department of Health. Archived from the original on 2014-02-03. Retrieved 2012-08-25.
  17. ^ Cataldi, Raffaele (August 1993). "Review of historiographic aspects of geothermal energy in the Mediterranean and Mesoamerican areas prior to the Modern Age" (PDF). Geo-Heat Centre Quarterly Bulletin. 15 (1): 13–16. ISSN 0276-1084. Archived from the original (PDF) on 2010-06-18. Retrieved 2009-11-01.
  18. ^ Bloomquist, R. Gordon (2001). Geothermal District Energy System Analysis, Design, and Development (PDF). International Summer School. International Geothermal Association. p. 213(1). Retrieved November 28, 2015. During Roman times, warm water was circulated through open trenches to provide heating for buildings and baths in Pompeii.
  19. ^ "A History of Geothermal Energy in the United States". US Department of Energy, Geothermal Technologies Program. Archived from the original on 2007-09-04. Retrieved 2007-09-10.
  20. ^ "One Hot Island: Iceland's Renewable Geothermal Power". Scientific American.
  21. ^ Dickson, Mary H.; Fanelli, Mario (February 2004). "What is Geothermal Energy?". Pisa, Italy: Istituto di Geoscienze e Georisorse. Archived from the original on 2009-10-09. Retrieved 2009-10-13.
  22. ^ a b Zogg, M. (20–22 May 2008). History of Heat Pumps: Swiss Contributions and International Milestones (PDF). Zürich, Switzerland: 9th International IEA Heat Pump Conference.
  23. ^ a b Bloomquist, R. Gordon (December 1999). "Geothermal Heat Pumps, Four Plus Decades of Experience" (PDF). Geo-Heat Centre Quarterly Bulletin. 20 (4): 13–18. ISSN 0276-1084. Archived from the original (PDF) on 2012-10-31. Retrieved 2009-03-21.
  24. ^ Kroeker, J. Donald; Chewning, Ray C. (February 1948). "A Heat Pump in an Office Building". ASHVE Transactions. 54: 221–238.
  25. ^ Gannon, Robert (February 1978). "Ground-Water Heat Pumps – Home Heating and Cooling from Your Own Well". Popular Science. 212 (2): 78–82. ISSN 0161-7370. Retrieved 2009-11-01.
  26. ^ Brown, D.W. (January 2000). "A Hot Dry Rock Geothermal Energy Concept Utilizing Supercritical CO2 Instead of Water" (PDF). Proceedings of Twenty-Fifth Workshop on Geothermal Reservoir Engineering Stanford University, Stanford, California, January 24-26, 2000: 233–238.
  27. ^ Atrens, A.D.; Gurgenci, H.; Rudolph, V. (2009). "CO2 Thermosiphon for Competitive Geothermal Power Generation". Energy Fuels. 23 (1): 553–557. doi:10.1021/ef800601z.
  28. ^ a b Lund, J.; Sanner, B.; Rybach, L.; Curtis, R.; Hellström, G. (September 2004). "Geothermal (Ground Source) Heat Pumps, A World Overview" (PDF). Geo-Heat Centre Quarterly Bulletin. 25 (3): 1–10. ISSN 0276-1084. Archived from the original (PDF) on 2014-02-01. Retrieved 2009-03-21.
  29. ^ "Geothermal Heat Pump Consortium, Inc". Retrieved 2008-04-27.
  30. ^ The Telegraph: Geothermal probe sinks German city (March 31, 2008)
  31. ^ Lubbadeh, Jens (15 November 2008). "Eine Stadt zerreißt" [A town rips up]. Spiegel Wissenschaft (in German). Partial translation.
  32. ^ Sass, Ingo; Burbaum, Ulrich (2010). "Damage to the historic town of Staufen (Germany) caused by geothermal drillings through anhydrite-bearing formations". Acta Carsologica. 39 (2): 233. doi:10.3986/ac.v39i2.96.
  33. ^ Butscher, Christoph; Huggenberger, Peter; Auckenthaler, Adrian; Bänninger, Dominik (2010). "Risikoorientierte Bewilligung von Erdwärmesonden" (PDF). Grundwasser. 16 (1): 13–24. Bibcode:2011Grund..16...13B. doi:10.1007/s00767-010-0154-5. S2CID 129598890.
  34. ^ Goldscheider, Nico; Bechtel, Timothy D. (2009). "Editors' message: The housing crisis from underground—damage to a historic town by geothermal drillings through anhydrite, Staufen, Germany". Hydrogeology Journal. 17 (3): 491–493. Bibcode:2009HydJ...17..491G. doi:10.1007/s10040-009-0458-7.
  35. ^ "TerraSAR-X Image Of The Month: Ground Uplift Under Staufen's Old Town". www.spacemart.com. SpaceDaily. 2009-10-22. Retrieved 2009-10-23.
  36. ^ De Giorgio, Giorgio; Chieco, Michele; Limoni, Pier Paolo; Zuffianò, Livia Emanuela; Dragone, Vittoria; Romanazzi, Annarita; Pagliarulo, Rossella; Musicco, Giuseppe; Polemio, Maurizio (2020-10-19). "Improving Regulation and the Role of Natural Risk Knowledge to Promote Sustainable Low Enthalpy Geothermal Energy Utilization". Water. 12 (10): 2925. doi:10.3390/w12102925. ISSN 2073-4441.
[edit]

 

 

An air filter being cleaned

Indoor air quality (IAQ) is the air quality within buildings and structures. Poor indoor air quality due to indoor air pollution is known to affect the health, comfort, and well-being of building occupants. It has also been linked to sick building syndrome, respiratory issues, reduced productivity, and impaired learning in schools. Common pollutants of indoor air include: secondhand tobacco smoke, air pollutants from indoor combustion, radon, molds and other allergens, carbon monoxide, volatile organic compounds, legionella and other bacteria, asbestos fibers, carbon dioxide,[1] ozone and particulates.

Source control, filtration, and the use of ventilation to dilute contaminants are the primary methods for improving indoor air quality. Although ventilation is an integral component of maintaining good indoor air quality, it may not be satisfactory alone.[2] In scenarios where outdoor pollution would deteriorate indoor air quality, other treatment devices such as filtration may also be necessary.[3]

IAQ is evaluated through collection of air samples, monitoring human exposure to pollutants, analysis of building surfaces, and computer modeling of air flow inside buildings. IAQ is part of indoor environmental quality (IEQ), along with other factors that exert an influence on physical and psychological aspects of life indoors (e.g., lighting, visual quality, acoustics, and thermal comfort).[4]

Indoor air pollution is a major health hazard in developing countries and is commonly referred to as "household air pollution" in that context.[5] It is mostly relating to cooking and heating methods by burning biomass fuel, in the form of wood, charcoal, dung, and crop residue, in indoor environments that lack proper ventilation. Millions of people, primarily women and children, face serious health risks. In total, about three billion people in developing countries are affected by this problem. The World Health Organization (WHO) estimates that cooking-related indoor air pollution causes 3.8 million annual deaths.[6] The Global Burden of Disease study estimated the number of deaths in 2017 at 1.6 million.[7]

Definition

[edit]

For health reasons it is crucial to breathe clean air, free from chemicals and toxicants as much as possible. It is estimated that humans spend approximately 90% of their lifetime indoors[8] and that indoor air pollution in some places can be much worse than that of the ambient air.[9][10]

Various factors contribute to high concentrations of pollutants indoors, ranging from influx of pollutants from external sources, off-gassing by furniture, furnishings including carpets, indoor activities (cooking, cleaning, painting, smoking, etc. in homes to using office equipment in offices), thermal comfort parameters such as temperature, humidity, airflow and physio-chemical properties of the indoor air.[citation needed] Air pollutants can enter a building in many ways, including through open doors or windows. Poorly maintained air conditioners/ventilation systems can harbor mold, bacteria, and other contaminants, which are then circulated throughout indoor spaces, contributing to respiratory problems and allergies.

There have been many debates among indoor air quality specialists about the proper definition of indoor air quality and specifically what constitutes "acceptable" indoor air quality.

Health effects

[edit]
Share of deaths from indoor air pollution. Darker colors mean higher numbers.

IAQ is significant for human health as humans spend a large proportion of their time in indoor environments. Americans and Europeans on average spend approximately 90% of their time indoors.[11][12]

The World Health Organization (WHO) estimates that 3.2 million people die prematurely every year from illnesses attributed to indoor air pollution caused by indoor cooking, with over 237 thousand of these being children under 5. These include around an eighth of all global ischaemic heart disease, stroke, and lung cancer deaths. Overall the WHO estimated that poor indoor air quality resulted in the loss of 86 million healthy life years in 2019.[13]

Studies in the UK and Europe show exposure to indoor air pollutants, chemicals and biological contamination can irritate the upper airway system, trigger or exacerbate asthma and other respiratory or cardiovascular conditions, and may even have carcinogenic effects.[14][15][16][17][18][19]

Poor indoor air quality can cause sick building syndrome. Symptoms include burning of the eyes, scratchy throat, blocked nose, and headaches.[20]

Common pollutants

[edit]

Generated by indoor combustion

[edit]
a 3-stone stove
A traditional wood-fired 3-stone stove in Guatemala, which causes indoor air pollution

Indoor combustion, such as for cooking or heating, is a major cause of indoor air pollution and causes significant health harms and premature deaths. Hydrocarbon fires cause air pollution. Pollution is caused by both biomass and fossil fuels of various types, but some forms of fuels are more harmful than others.

Indoor fire can produce black carbon particles, nitrogen oxides, sulfur oxides, and mercury compounds, among other emissions.[21] Around 3 billion people cook over open fires or on rudimentary cook stoves. Cooking fuels are coal, wood, animal dung, and crop residues.[22] IAQ is a particular concern in low and middle-income countries where such practices are common.[23]

Cooking using natural gas (also called fossil gas, methane gas or simply gas) is associated with poorer indoor air quality. Combustion of gas produces nitrogen dioxide and carbon monixide, and can lead to increased concentrations of nitrogen dioxide throughout the home environment which is linked to respiratory issues and diseases.[24][25]

Carbon monoxide

[edit]

One of the most acutely toxic indoor air contaminants is carbon monoxide (CO), a colourless and odourless gas that is a by-product of incomplete combustion. Carbon monoxide may be emitted from tobacco smoke and generated from malfunctioning fuel burning stoves (wood, kerosene, natural gas, propane) and fuel burning heating systems (wood, oil, natural gas) and from blocked flues connected to these appliances.[26] In developed countries the main sources of indoor CO emission come from cooking and heating devices that burn fossil fuels and are faulty, incorrectly installed or poorly maintained.[27] Appliance malfunction may be due to faulty installation or lack of maintenance and proper use.[26] In low- and middle-income countries the most common sources of CO in homes are burning biomass fuels and cigarette smoke.[27]

Health effects of CO poisoning may be acute or chronic and can occur unintentionally or intentionally (self-harm). By depriving the brain of oxygen, acute exposure to carbon monoxide may have effects on the neurological system (headache, nausea, dizziness, alteration in consciousness and subjective weakness), the cardiovascular and respiratory systems (myocardial infarction, shortness of breath, or rapid breathing, respiratory failure). Acute exposure can also lead to long-term neurological effects such as cognitive and behavioural changes. Severe CO poisoning may lead to unconsciousness, coma and death. Chronic exposure to low concentrations of carbon monoxide may lead to lethargy, headaches, nausea, flu-like symptoms and neuropsychological and cardiovascular issues.[28][26]

The WHO recommended levels of indoor CO exposure in 24 hours is 4 mg/m3.[29] Acute exposure should not exceed 10 mg/m3 in 8 hours, 35 mg/m3 in one hour and 100 mg/m3 in 15 minutes.[27]

Secondhand tobacco smoke

[edit]

Secondhand smoke is tobacco smoke which affects people other than the 'active' smoker. It is made up of the exhaled smoke (15%) and mostly of smoke coming from the burning end of the cigarette, known as sidestream smoke (85%).[30]

Secondhand smoke contains more than 7000 chemicals, of which hundreds are harmful to health.[30] Secondhand tobacco smoke includes both a gaseous and a particulate materials which, with particular hazards arising from levels of carbon monoxide and very small particulates (fine particulate matter, especially PM2.5 and PM10) which get into the bronchioles and alveoles in the lung.[31] Inhaling secondhand smoke on multiple occasions can cause asthma, pneumonia, lung cancer, and sudden infant death syndrome, among other conditions.[32]

Thirdhand smoke (THS) refers to chemicals that settle on objects and bodies indoors after smoking. Exposure to thirdhand smoke can happen even after the actual cigarette smoke is not present anymore and affect those entering the indoor environment much later. Toxic substances of THS can react with other chemicals in the air and produce new toxic chemicals that are otherwise not present in cigarettes.[33]

The only certain method to improve indoor air quality as regards secondhand smoke is to eliminate smoking indoors.[34] Indoor e-cigarette use also increases home particulate matter concentrations.[35]

Particulates

[edit]

Atmospheric particulate matter, also known as particulates, can be found indoors and can affect the health of occupants. Indoor particulate matter can come from different indoor sources or be created as secondary aerosols through indoor gas-to-particle reactions. They can also be outdoor particles that enter indoors. These indoor particles vary widely in size, ranging from nanomet (nanoparticles/ultrafine particles emitted from combustion sources) to micromet (resuspensed dust).[36] Particulate matter can also be produced through cooking activities. Frying produces higher concentrations than boiling or grilling and cooking meat produces higher concentrations than cooking vegetables.[37] Preparing a Thanksgiving dinner can produce very high concentrations of particulate matter, exceeding 300 μg/m3.[38]

Particulates can penetrate deep into the lungs and brain from blood streams, causing health problems such as heart disease, lung disease, cancer and preterm birth.[39]

Generated from building materials, furnishing and consumer products

[edit]

Volatile organic compounds

[edit]

Volatile organic compounds (VOCs) include a variety of chemicals, some of which may have short- and long-term adverse health effects. There are numerous sources of VOCs indoors, which means that their concentrations are consistently higher indoors (up to ten times higher) than outdoors.[40] Some VOCs are emitted directly indoors, and some are formed through the subsequent chemical reactions that can occur in the gas-phase, or on surfaces.[41][42] VOCs presenting health hazards include benzene, formaldehyde, tetrachloroethylene and trichloroethylene.[43]

VOCs are emitted by thousands of indoor products. Examples include: paints, varnishes, waxes and lacquers, paint strippers, cleaning and personal care products, pesticides, building materials and furnishings, office equipment such as copiers and printers, correction fluids and carbonless copy paper, graphics and craft materials including glues and adhesives, permanent markers, and photographic solutions.[44] Chlorinated drinking water releases chloroform when hot water is used in the home. Benzene is emitted from fuel stored in attached garages.

Human activities such as cooking and cleaning can also emit VOCs.[45][46] Cooking can release long-chain aldehydes and alkanes when oil is heated and terpenes can be released when spices are prepared and/or cooked.[45] Leaks of natural gas from cooking appliances have been linked to elevated levels of VOCs including benzene in homes in the USA.[47] Cleaning products contain a range of VOCs, including monoterpenes, sesquiterpenes, alcohols and esters. Once released into the air, VOCs can undergo reactions with ozone and hydroxyl radicals to produce other VOCs, such as formaldehyde.[46]

Health effects include eye, nose, and throat irritation; headaches, loss of coordination, nausea; and damage to the liver, kidney, and central nervous system.[48]

Testing emissions from building materials used indoors has become increasingly common for floor coverings, paints, and many other important indoor building materials and finishes.[49] Indoor materials such as gypsum boards or carpet act as VOC 'sinks', by trapping VOC vapors for extended periods of time, and releasing them by outgassing. The VOCs can also undergo transformation at the surface through interaction with ozone.[42] In both cases, these delayed emissions can result in chronic and low-level exposures to VOCs.[50]

Several initiatives aim to reduce indoor air contamination by limiting VOC emissions from products. There are regulations in France and in Germany, and numerous voluntary ecolabels and rating systems containing low VOC emissions criteria such as EMICODE,[51] M1,[52] Blue Angel[53] and Indoor Air Comfort[54] in Europe, as well as California Standard CDPH Section 01350[55] and several others in the US. Due to these initiatives an increasing number of low-emitting products became available to purchase.

At least 18 microbial VOCs (MVOCs) have been characterised[56][57] including 1-octen-3-ol (mushroom alcohol), 3-Methylfuran, 2-pentanol, 2-hexanone, 2-heptanone, 3-octanone, 3-octanol, 2-octen-1-ol, 1-octene, 2-pentanone, 2-nonanone, borneol, geosmin, 1-butanol, 3-methyl-1-butanol, 3-methyl-2-butanol, and thujopsene. The last four are products of Stachybotrys chartarum, which has been linked with sick building syndrome.[56]

Asbestos fibers

[edit]

Many common building materials used before 1975 contain asbestos, such as some floor tiles, ceiling tiles, shingles, fireproofing, heating systems, pipe wrap, taping muds, mastics, and other insulation materials. Normally, significant releases of asbestos fiber do not occur unless the building materials are disturbed, such as by cutting, sanding, drilling, or building remodelling. Removal of asbestos-containing materials is not always optimal because the fibers can be spread into the air during the removal process. A management program for intact asbestos-containing materials is often recommended instead.

When asbestos-containing material is damaged or disintegrates, microscopic fibers are dispersed into the air. Inhalation of asbestos fibers over long exposure times is associated with increased incidence of lung cancer, mesothelioma, and asbestosis. The risk of lung cancer from inhaling asbestos fibers is significantly greater for smokers. The symptoms of disease do not usually appear until about 20 to 30 years after the first exposure to asbestos.

Although all asbestos is hazardous, products that are friable, e.g. sprayed coatings and insulation, pose a significantly higher hazard as they are more likely to release fibers to the air.[58]

Microplastics

[edit]

Microplastic is a type of airborne particulates and is found to prevail in air.[59][60][61][62] A 2017 study found indoor airborne microfiber concentrations between 1.0 and 60.0 microfibers per cubic meter (33% of which were found to be microplastics).[63] Airborne microplastic dust can be produced during renovation, building, bridge and road reconstruction projects[64] and the use of power tools.[65]

Ozone

[edit]

Indoors ozone (O3) is produced by certain high-voltage electric devices (such as air ionizers), and as a by-product of other types of pollution. It appears in lower concentrations indoors than outdoors, usually at 0.2-0.7 of the outdoor concentration.[66] Typically, most ozone is lost to surface reactions indoors, rather than to reactions in air, due to the large surface to volume ratios found indoors.[67]

Outdoor air used for ventilation may have sufficient ozone to react with common indoor pollutants as well as skin oils and other common indoor air chemicals or surfaces. Particular concern is warranted when using "green" cleaning products based on citrus or terpene extracts, because these chemicals react very quickly with ozone to form toxic and irritating chemicals[46] as well as fine and ultrafine particles.[68] Ventilation with outdoor air containing elevated ozone concentrations may complicate remediation attempts.[69]

The WHO standard for ozone concentration is 60 μg/m3 for long-term exposure and 100 μg/m3 as the maximum average over an 8-hour period.[29] The EPA standard for ozone concentration is 0.07 ppm average over an 8-hour period.[70]

Biological agents

[edit]

Mold and other allergens

[edit]

Occupants in buildings can be exposed to fungal spores, cell fragments, or mycotoxins which can arise from a host of means, but there are two common classes: (a) excess moisture induced growth of mold colonies and (b) natural substances released into the air such as animal dander and plant pollen.[71]

While mold growth is associated with high moisture levels,[72] it is likely to grow when a combination of favorable conditions arises. As well as high moisture levels, these conditions include suitable temperatures, pH and nutrient sources.[73] Mold grows primarily on surfaces, and it reproduces by releasing spores, which can travel and settle in different locations. When these spores experience appropriate conditions, they can germinate and lead to mycelium growth.[74] Different mold species favor different environmental conditions to germinate and grow, some being more hydrophilic (growing at higher levels of relative humidity) and other more xerophilic (growing at levels of relative humidity as low as 75–80%).[74][75]

Mold growth can be inhibited by keeping surfaces at conditions that are further from condensation, with relative humidity levels below 75%. This usually translates to a relative humidity of indoor air below 60%, in agreement with the guidelines for thermal comfort that recommend a relative humidity between 40 and 60 %. Moisture buildup in buildings may arise from water penetrating areas of the building envelope or fabric, from plumbing leaks, rainwater or groundwater penetration, or from condensation due to improper ventilation, insufficient heating or poor thermal quality of the building envelope.[76] Even something as simple as drying clothes indoors on radiators can increase the risk of mold growth, if the humidity produced is not able to escape the building via ventilation.[77]

Mold predominantly affects the airways and lungs. Known effects of mold on health include asthma development and exacerbation,[78] with children and elderly at greater risk of more severe health impacts.[79] Infants in homes with mold have a much greater risk of developing asthma and allergic rhinitis.[80][71] More than half of adult workers in moldy or humid buildings suffer from nasal or sinus symptoms due to mold exposure.[71] Some varieties of mold contain toxic compounds (mycotoxins). However, exposure to hazardous levels of mycotoxin via inhalation is not possible in most cases, as toxins are produced by the fungal body and are not at significant levels in the released spores.

Legionella

[edit]

Legionnaires' disease is caused by a waterborne bacterium Legionella that grows best in slow-moving or still, warm water. The primary route of exposure is through the creation of an aerosol effect, most commonly from evaporative cooling towers or showerheads. A common source of Legionella in commercial buildings is from poorly placed or maintained evaporative cooling towers, which often release water in an aerosol which may enter nearby ventilation intakes. Outbreaks in medical facilities and nursing homes, where patients are immuno-suppressed and immuno-weak, are the most commonly reported cases of Legionellosis. More than one case has involved outdoor fountains at public attractions. The presence of Legionella in commercial building water supplies is highly under-reported, as healthy people require heavy exposure to acquire infection.

Legionella testing typically involves collecting water samples and surface swabs from evaporative cooling basins, shower heads, faucets/taps, and other locations where warm water collects. The samples are then cultured and colony forming units (cfu) of Legionella are quantified as cfu/liter.

Legionella is a parasite of protozoans such as amoeba, and thus requires conditions suitable for both organisms. The bacterium forms a biofilm which is resistant to chemical and antimicrobial treatments, including chlorine. Remediation for Legionella outbreaks in commercial buildings vary, but often include very hot water flushes (160 °F (71 °C)), sterilisation of standing water in evaporative cooling basins, replacement of shower heads, and, in some cases, flushes of heavy metal salts. Preventive measures include adjusting normal hot water levels to allow for 120 °F (49 °C) at the tap, evaluating facility design layout, removing faucet aerators, and periodic testing in suspect areas.

Other bacteria

[edit]
Airborne bacteria

There are many bacteria of health significance found in indoor air and on indoor surfaces. The role of microbes in the indoor environment is increasingly studied using modern gene-based analysis of environmental samples. Currently, efforts are under way to link microbial ecologists and indoor air scientists to forge new methods for analysis and to better interpret the results.[81]

A large fraction of the bacteria found in indoor air and dust are shed from humans. Among the most important bacteria known to occur in indoor air are Mycobacterium tuberculosis, Staphylococcus aureus, Streptococcus pneumoniae.[citation needed]

Virus

[edit]
Ninth floor layout of the Metropole Hotel in Hong Kong, showing where an outbreak of the severe acute respiratory syndrome (SARS) occurred

Viruses can also be a concern for indoor air quality. During the 2002–2004 SARS outbreak, virus-laden aerosols were found to have seeped into bathrooms from the bathroom floor drains, exacerbated by the draw of bathroom exhaust fans, resulting in the rapid spread of SARS in Amoy Gardens in Hong Kong.[82][83] Elsewhere in Hong Kong, SARS CoV RNA was found on the carpet and in the air intake vents of the Metropole Hotel, which showed that secondary environmental contamination could generate infectious aerosols and resulted in superspreading events.[84]

Carbon dioxide

[edit]

Humans are the main indoor source of carbon dioxide (CO2) in most buildings. Indoor CO2 levels are an indicator of the adequacy of outdoor air ventilation relative to indoor occupant density and metabolic activity.

Indoor CO2 levels above 500 ppm can lead to higher blood pressure and heart rate, and increased peripheral blood circulation.[85] With CO2 concentrations above 1000 ppm cognitive performance might be affected, especially when doing complex tasks, making decision making and problem solving slower but not less accurate.[86][87] However, evidence on the health effects of CO2 at lower concentrations is conflicting and it is difficult to link CO2 to health impacts at exposures below 5000 ppm – reported health outcomes may be due to the presence of human bioeffluents, and other indoor air pollutants related to inadequate ventilation.[88]

Indoor carbon dioxide concentrations can be used to evaluate the quality of a room or a building's ventilation.[89] To eliminate most complaints caused by CO2, the total indoor CO2 level should be reduced to a difference of no greater than 700 ppm above outdoor levels.[90] The National Institute for Occupational Safety and Health (NIOSH) considers that indoor air concentrations of carbon dioxide that exceed 1000 ppm are a marker suggesting inadequate ventilation.[91] The UK standards for schools say that carbon dioxide levels of 800 ppm or lower indicate that the room is well-ventilated.[92] Regulations and standards from around the world show that CO2 levels below 1000 ppm represent good IAQ, between 1000 and 1500 ppm represent moderate IAQ and greater than 1500 ppm represent poor IAQ.[88]

Carbon dioxide concentrations in closed or confined rooms can increase to 1,000 ppm within 45 minutes of enclosure. For example, in a 3.5-by-4-metre (11 ft × 13 ft) sized office, atmospheric carbon dioxide increased from 500 ppm to over 1,000 ppm within 45 minutes of ventilation cessation and closure of windows and doors.[93]

Radon

[edit]

Radon is an invisible, radioactive atomic gas that results from the radioactive decay of radium, which may be found in rock formations beneath buildings or in certain building materials themselves.

Radon is probably the most pervasive serious hazard for indoor air in the United States and Europe. It is a major cause of lung cancer, responsible for 3–14% of cases in countries, leading to tens of thousands of deaths.[94]

Radon gas enters buildings as a soil gas. As it is a heavy gas it will tend to accumulate at the lowest level. Radon may also be introduced into a building through drinking water particularly from bathroom showers. Building materials can be a rare source of radon, but little testing is carried out for stone, rock or tile products brought into building sites; radon accumulation is greatest for well insulated homes.[95] There are simple do-it-yourself kits for radon gas testing, but a licensed professional can also check homes.

The half-life for radon is 3.8 days, indicating that once the source is removed, the hazard will be greatly reduced within a few weeks. Radon mitigation methods include sealing concrete slab floors, basement foundations, water drainage systems, or by increasing ventilation.[96] They are usually cost effective and can greatly reduce or even eliminate the contamination and the associated health risks.[citation needed]

Radon is measured in picocuries per liter of air (pCi/L) or becquerel per cubic meter (Bq m-3). Both are measurements of radioactivity. The World Health Organization (WHO) sets the ideal indoor radon levels at 100 Bq/m-3.[97] In the United States, it is recommend to fix homes with radon levels at or above 4 pCi/L. At the same time it is also recommends that people think about fixing their homes for radon levels between 2 pCi/L and 4 pCi/L.[98] In the United Kingdom the ideal is presence of radon indoors is 100 Bq/m-3. Action needs to be taken in homes with 200 Bq/m−3 or more.[99]

Interactive maps of radon affected areas are available for various regions and countries of the world.[100][101][102]

IAQ and climate change

[edit]

Indoor air quality is linked inextricably to outdoor air quality. The Intergovernmental Panel on Climate Change (IPCC) has varying scenarios that predict how the climate will change in the future.[103] Climate change can affect indoor air quality by increasing the level of outdoor air pollutants such as ozone and particulate matter, for example through emissions from wildfires caused by extreme heat and drought.[104][105] Numerous predictions for how indoor air pollutants will change have been made,[106][107][108][109] and models have attempted to predict how the forecasted IPCC scenarios will vary indoor air quality and indoor comfort parameters such as humidity and temperature.[110]

The net-zero challenge requires significant changes in the performance of both new and retrofitted buildings. However, increased energy efficient housing will trap pollutants inside, whether produced indoors or outdoors, and lead to an increase in human exposure.[111][112]

Indoor air quality standards and monitoring

[edit]

Quality guidelines and standards

[edit]

For occupational exposure, there are standards, which cover a wide range of chemicals, and applied to healthy adults who are exposed over time at workplaces (usually industrial environments).These are published by organisations such as Occupational Safety and Health Administration (OSHA), the National Institute for Occupational Safety and Health (NIOSH), the UK Health and Safety Executive (HSE).

There is no consensus globally about indoor air quality standards, or health-based guidelines. However, there are regulations from some individual countries and from health organisations. For example, the World Health Organization (WHO) has published health-based global air quality guidelines for the general population that are applicable both to outdoor and indoor air,[29] as well as the WHO IAQ guidelines for selected compounds,[113] whereas the UK Health Security Agency published IAQ guidelines for selected VOCs.[114] The Scientific and Technical Committee (STC34) of the International Society of Indoor Air Quality and Climate (ISIAQ) created an open database that collects indoor environmental quality guidelines worldwide.[115] The database is focused on indoor air quality (IAQ), but is currently extended to include standards, regulations, and guidelines related to ventilation, comfort, acoustics, and lighting.[116][117]

Real-time monitoring

[edit]

Since indoor air pollutants can adversely affect human health, it is important to have real-time indoor air quality assessment/monitoring system that can help not only in the improvement of indoor air quality but also help in detection of leaks, spills in a work environment and boost energy efficiency of buildings by providing real-time feedback to the heating, ventilation, and air conditioning (HVAC) system(s).[118] Additionally, there have been enough studies that highlight the correlation between poor indoor air quality and loss of performance and productivity of workers in an office setting.[119]  

Combining the Internet of Things (IoT) technology with real-time IAQ monitoring systems has  tremendously gained momentum and popularity as interventions can be done based on the real-time sensor data and thus help in the IAQ improvement.[120]   

Improvement measures

[edit]

Indoor air quality can be addressed, achieved or maintained during the design of new buildings or as mitigating measures in existing buildings. A hierarchy of measures has been proposed by the Institute of Air Quality Management. It emphasises removing pollutant sources, reducing emissions from any remaining sources, disrupting pathways between sources and the people exposed, protecting people from exposure to pollutants, and removing people from areas with poor air quality.[121]

A report assisted by the Institute for Occupational Safety and Health of the German Social Accident Insurance can support in the systematic investigation of individual health problems arising at indoor workplaces, and in the identification of practical solutions.[122]

Source control

[edit]

HVAC design

[edit]

Environmentally sustainable design concepts include aspects of commercial and residential heating, ventilation and air-conditioning (HVAC) technologies. Among several considerations, one of the topics attended to is the issue of indoor air quality throughout the design and construction stages of a building's life.[citation needed]

One technique to reduce energy consumption while maintaining adequate air quality, is demand-controlled ventilation. Instead of setting throughput at a fixed air replacement rate, carbon dioxide sensors are used to control the rate dynamically, based on the emissions of actual building occupants.[citation needed]

One way of quantitatively ensuring the health of indoor air is by the frequency of effective turnover of interior air by replacement with outside air. In the UK, for example, classrooms are required to have 2.5 outdoor air changes per hour. In halls, gym, dining, and physiotherapy spaces, the ventilation should be sufficient to limit carbon dioxide to 1,500 ppm. In the US, ventilation in classrooms is based on the amount of outdoor air per occupant plus the amount of outdoor air per unit of floor area, not air changes per hour. Since carbon dioxide indoors comes from occupants and outdoor air, the adequacy of ventilation per occupant is indicated by the concentration indoors minus the concentration outdoors. The value of 615 ppm above the outdoor concentration indicates approximately 15 cubic feet per minute of outdoor air per adult occupant doing sedentary office work where outdoor air contains over 400 ppm[123] (global average as of 2023). In classrooms, the requirements in the ASHRAE standard 62.1, Ventilation for Acceptable Indoor Air Quality, would typically result in about 3 air changes per hour, depending on the occupant density. As the occupants are not the only source of pollutants, outdoor air ventilation may need to be higher when unusual or strong sources of pollution exist indoors.

When outdoor air is polluted, bringing in more outdoor air can actually worsen the overall quality of the indoor air and exacerbate some occupant symptoms related to outdoor air pollution. Generally, outdoor country air is better than indoor city air.[citation needed]

The use of air filters can trap some of the air pollutants. Portable room air cleaners with HEPA filters can be used if ventilation is poor or outside air has high level of PM 2.5.[122] Air filters are used to reduce the amount of dust that reaches the wet coils.[citation needed] Dust can serve as food to grow molds on the wet coils and ducts and can reduce the efficiency of the coils.[citation needed]

The use of trickle vents on windows is also valuable to maintain constant ventilation. They can help prevent mold and allergen build up in the home or workplace. They can also reduce the spread of some respiratory infections.[124]

Moisture management and humidity control requires operating HVAC systems as designed. Moisture management and humidity control may conflict with efforts to conserve energy. For example, moisture management and humidity control requires systems to be set to supply make-up air at lower temperatures (design levels), instead of the higher temperatures sometimes used to conserve energy in cooling-dominated climate conditions. However, for most of the US and many parts of Europe and Japan, during the majority of hours of the year, outdoor air temperatures are cool enough that the air does not need further cooling to provide thermal comfort indoors.[citation needed] However, high humidity outdoors creates the need for careful attention to humidity levels indoors. High humidity give rise to mold growth and moisture indoors is associated with a higher prevalence of occupant respiratory problems.[citation needed]

The "dew point temperature" is an absolute measure of the moisture in air. Some facilities are being designed with dew points in the lower 50s °F, and some in the upper and lower 40s °F.[citation needed] Some facilities are being designed using desiccant wheels with gas-fired heaters to dry out the wheel enough to get the required dew points.[citation needed] On those systems, after the moisture is removed from the make-up air, a cooling coil is used to lower the temperature to the desired level.[citation needed]

Commercial buildings, and sometimes residential, are often kept under slightly positive air pressure relative to the outdoors to reduce infiltration. Limiting infiltration helps with moisture management and humidity control.

Dilution of indoor pollutants with outdoor air is effective to the extent that outdoor air is free of harmful pollutants. Ozone in outdoor air occurs indoors at reduced concentrations because ozone is highly reactive with many chemicals found indoors. The products of the reactions between ozone and many common indoor pollutants include organic compounds that may be more odorous, irritating, or toxic than those from which they are formed. These products of ozone chemistry include formaldehyde, higher molecular weight aldehydes, acidic aerosols, and fine and ultrafine particles, among others. The higher the outdoor ventilation rate, the higher the indoor ozone concentration and the more likely the reactions will occur, but even at low levels, the reactions will take place. This suggests that ozone should be removed from ventilation air, especially in areas where outdoor ozone levels are frequently high.

Effect of indoor plants

[edit]
Spider plants (Chlorophytum comosum) absorb some airborne contaminants.

Houseplants together with the medium in which they are grown can reduce components of indoor air pollution, particularly volatile organic compounds (VOC) such as benzene, toluene, and xylene. Plants remove CO2 and release oxygen and water, although the quantitative impact for house plants is small. The interest in using potted plants for removing VOCs was sparked by a 1989 NASA study conducted in sealed chambers designed to replicate the environment on space stations. However, these results suffered from poor replication[125] and are not applicable to typical buildings, where outdoor-to-indoor air exchange already removes VOCs at a rate that could only be matched by the placement of 10–1000 plants/m2 of a building's floor space.[126]

Plants also appear to reduce airborne microbes and molds, and to increase humidity.[127] However, the increased humidity can itself lead to increased levels of mold and even VOCs.[128]

Since extremely high humidity is associated with increased mold growth, allergic responses, and respiratory responses, the presence of additional moisture from houseplants may not be desirable in all indoor settings if watering is done inappropriately.[129]

Institutional programs

[edit]
EPA graphic about asthma triggers

The topic of IAQ has become popular due to the greater awareness of health problems caused by mold and triggers to asthma and allergies.

In the US, the Environmental Protection Agency (EPA) has developed an "IAQ Tools for Schools" program to help improve the indoor environmental conditions in educational institutions. The National Institute for Occupational Safety and Health conducts Health Hazard Evaluations (HHEs) in workplaces at the request of employees, authorized representative of employees, or employers, to determine whether any substance normally found in the place of employment has potentially toxic effects, including indoor air quality.[130]

A variety of scientists work in the field of indoor air quality, including chemists, physicists, mechanical engineers, biologists, bacteriologists, epidemiologists, and computer scientists. Some of these professionals are certified by organizations such as the American Industrial Hygiene Association, the American Indoor Air Quality Council and the Indoor Environmental Air Quality Council.

In the UK, under the Department for Environment Food and Rural Affairs, the Air Quality Expert Group considers current knowledge on indoor air quality and provides advice to government and devolved administration ministers.[131]

At the international level, the International Society of Indoor Air Quality and Climate (ISIAQ), formed in 1991, organizes two major conferences, the Indoor Air and the Healthy Buildings series.[132]

See also

[edit]

References

[edit]
  1. ^ Carroll, GT; Kirschman, DL; Mammana, A (2022). "Increased CO2 levels in the operating room correlate with the number of healthcare workers present: an imperative for intentional crowd control". Patient Safety in Surgery. 16 (35): 35. doi:10.1186/s13037-022-00343-8. PMC 9672642. PMID 36397098.
  2. ^ ANSI/ASHRAE Standard 62.1, Ventilation for Acceptable Indoor Air Quality, ASHRAE, Inc., Atlanta, GA, US
  3. ^ Belias, Evangelos; Licina, Dusan (2022). "Outdoor PM2. 5 air filtration: optimising indoor air quality and energy". Building & Cities. 3 (1): 186–203. doi:10.5334/bc.153.
  4. ^ KMC Controls (September 24, 2015). "What's Your IQ on IAQ and IEQ?". Archived from the original on April 12, 2021. Retrieved April 12, 2021.[unreliable source?]
  5. ^ Bruce, N; Perez-Padilla, R; Albalak, R (2000). "Indoor air pollution in developing countries: a major environmental and public health challenge". Bulletin of the World Health Organization. 78 (9): 1078–92. PMC 2560841. PMID 11019457.
  6. ^ "Household air pollution and health: fact sheet". WHO. May 8, 2018. Archived from the original on November 12, 2021. Retrieved November 21, 2020.
  7. ^ Ritchie, Hannah; Roser, Max (2019). "Access to Energy". Our World in Data. Archived from the original on November 1, 2021. Retrieved April 1, 2021. According to the Global Burden of Disease study 1.6 million people died prematurely in 2017 as a result of indoor air pollution ... But it's worth noting that the WHO publishes a substantially larger number of indoor air pollution deaths..
  8. ^ Klepeis, Neil E; Nelson, William C; Ott, Wayne R; Robinson, John P; Tsang, Andy M; Switzer, Paul; Behar, Joseph V; Hern, Stephen C; Engelmann, William H (July 2001). "The National Human Activity Pattern Survey (NHAPS): a resource for assessing exposure to environmental pollutants". Journal of Exposure Science & Environmental Epidemiology. 11 (3): 231–252. Bibcode:2001JESEE..11..231K. doi:10.1038/sj.jea.7500165. PMID 11477521. S2CID 22445147. Archived from the original on March 28, 2023. Retrieved March 30, 2024.
  9. ^ U.S. Environmental Protection Agency. Office equipment: design, indoor air emissions, and pollution prevention opportunities. Air and Energy Engineering Research Laboratory, Research Triangle Park, 1995.
  10. ^ U.S. Environmental Protection Agency. Unfinished business: a comparative assessment of environmental problems, EPA-230/2-87-025a-e (NTIS PB88-127030). Office of Policy, Planning and Evaluation, Washington, DC, 1987.
  11. ^ Klepeis, Neil E; Nelson, William C; Ott, Wayne R; Robinson, John P; Tsang, Andy M; Switzer, Paul; Behar, Joseph V; Hern, Stephen C; Engelmann, William H (July 1, 2001). "The National Human Activity Pattern Survey (NHAPS): a resource for assessing exposure to environmental pollutants". Journal of Exposure Science & Environmental Epidemiology. 11 (3): 231–252. Bibcode:2001JESEE..11..231K. doi:10.1038/sj.jea.7500165. ISSN 1559-0631. PMID 11477521. Archived from the original on November 13, 2023. Retrieved November 13, 2023.
  12. ^ "Combined or multiple exposure to health stressors in indoor built environments: an evidence-based review prepared for the WHO training workshop "Multiple environmental exposures and risks": 16–18 October 2013, Bonn, Germany". World Health Organization. Regional Office for Europe. 2014. Archived from the original on November 6, 2023. Retrieved April 10, 2024.
  13. ^ "Household air pollution". World Health Organization. December 15, 2023. Archived from the original on November 12, 2021. Retrieved April 10, 2024.
  14. ^ Clark, Sierra N.; Lam, Holly C. Y.; Goode, Emma-Jane; Marczylo, Emma L.; Exley, Karen S.; Dimitroulopoulou, Sani (August 2, 2023). "The Burden of Respiratory Disease from Formaldehyde, Damp and Mould in English Housing". Environments. 10 (8): 136. doi:10.3390/environments10080136. ISSN 2076-3298.
  15. ^ "Chief Medical Officer (CMO): annual reports". GOV.UK. November 16, 2023. Retrieved May 5, 2024.
  16. ^ "Project information | Indoor air quality at home | Quality standards | NICE". www.nice.org.uk. Retrieved May 5, 2024.
  17. ^ "The inside story: Health effects of indoor air quality on children and young people". RCPCH. Retrieved May 5, 2024.
  18. ^ Halios, Christos H.; Landeg-Cox, Charlotte; Lowther, Scott D.; Middleton, Alice; Marczylo, Tim; Dimitroulopoulou, Sani (September 15, 2022). "Chemicals in European residences – Part I: A review of emissions, concentrations and health effects of volatile organic compounds (VOCs)". Science of the Total Environment. 839: 156201. Bibcode:2022ScTEn.83956201H. doi:10.1016/j.scitotenv.2022.156201. ISSN 0048-9697. PMID 35623519.
  19. ^ "Literature review on chemical pollutants in indoor air in public settings for children and overview of their health effects with a focus on schools, kindergartens and day-care centres". www.who.int. Retrieved May 5, 2024.
  20. ^ Burge, P S (February 2004). "Sick building syndrome". Occupational and Environmental Medicine. 61 (2): 185–190. doi:10.1136/oem.2003.008813. PMC 1740708. PMID 14739390.
  21. ^ Apte, K; Salvi, S (2016). "Household air pollution and its effects on health". F1000Research. 5: 2593. doi:10.12688/f1000research.7552.1. PMC 5089137. PMID 27853506. Burning of natural gas not only produces a variety of gases such as sulfur oxides, mercury compounds, and particulate matter but also leads to the production of nitrogen oxides, primarily nitrogen dioxide...The burning of biomass fuel or any other fossil fuel increases the concentration of black carbon in the air
  22. ^ "Improved Clean Cookstoves". Project Drawdown. February 7, 2020. Archived from the original on December 15, 2021. Retrieved December 5, 2020.
  23. ^ WHO indoor air quality guidelines: household fuel combustion. Geneva: World Health Organization. 2014. ISBN 978-92-4-154888-5.
  24. ^ "Clearing the Air: Gas Cooking and Pollution in European Homes". CLASP. November 8, 2023. Retrieved May 5, 2024.
  25. ^ Seals, Brady; Krasner, Andee. "Gas Stoves: Health and Air Quality Impacts and Solutions". RMI. Retrieved May 5, 2024.
  26. ^ a b c Myers, Isabella (February 2022). The efficient operation of regulation and legislation: An holistic approach to understanding the effect of Carbon Monoxide on mortality (PDF). CO Research Trust.
  27. ^ a b c Penney, David; Benignus, Vernon; Kephalopoulos, Stylianos; Kotzias, Dimitrios; Kleinman, Michael; Verrier, Agnes (2010), "Carbon monoxide", WHO Guidelines for Indoor Air Quality: Selected Pollutants, World Health Organization, ISBN 978-92-890-0213-4, OCLC 696099951, archived from the original on March 8, 2021, retrieved March 18, 2024
  28. ^ "Carbon monoxide: toxicological overview". UK Health Security Agency. May 24, 2022. Retrieved April 17, 2024.
  29. ^ a b c WHO global air quality guidelines: particulate matter (PM2.5 and PM10), ozone, nitrogen dioxide, sulfur dioxide and carbon monoxide (PDF). World Health Organization. 2021. hdl:10665/345329. ISBN 978-92-4-003422-8.[page needed]
  30. ^ a b Soleimani, Farshid; Dobaradaran, Sina; De-la-Torre, Gabriel E.; Schmidt, Torsten C.; Saeedi, Reza (March 2022). "Content of toxic components of cigarette, cigarette smoke vs cigarette butts: A comprehensive systematic review". Science of the Total Environment. 813: 152667. Bibcode:2022ScTEn.81352667S. doi:10.1016/j.scitotenv.2021.152667. PMID 34963586.
  31. ^ "Considering smoking as an air pollution problem for environmental health | Environmental Performance Index". Archived from the original on September 25, 2018. Retrieved March 21, 2018.
  32. ^ Arfaeinia, Hossein; Ghaemi, Maryam; Jahantigh, Anis; Soleimani, Farshid; Hashemi, Hassan (June 12, 2023). "Secondhand and thirdhand smoke: a review on chemical contents, exposure routes, and protective strategies". Environmental Science and Pollution Research. 30 (32): 78017–78029. Bibcode:2023ESPR...3078017A. doi:10.1007/s11356-023-28128-1. PMC 10258487. PMID 37306877.
  33. ^ Arfaeinia, Hossein; Ghaemi, Maryam; Jahantigh, Anis; Soleimani, Farshid; Hashemi, Hassan (June 12, 2023). "Secondhand and thirdhand smoke: a review on chemical contents, exposure routes, and protective strategies". Environmental Science and Pollution Research. 30 (32): 78017–78029. Bibcode:2023ESPR...3078017A. doi:10.1007/s11356-023-28128-1. ISSN 1614-7499. PMC 10258487. PMID 37306877.
  34. ^ Health, CDC's Office on Smoking and (May 9, 2018). "Smoking and Tobacco Use; Fact Sheet; Secondhand Smoke". Smoking and Tobacco Use. Archived from the original on December 15, 2021. Retrieved January 14, 2019.
  35. ^ Fernández, E; Ballbè, M; Sureda, X; Fu, M; Saltó, E; Martínez-Sánchez, JM (December 2015). "Particulate Matter from Electronic Cigarettes and Conventional Cigarettes: a Systematic Review and Observational Study". Current Environmental Health Reports. 2 (4): 423–9. Bibcode:2015CEHR....2..423F. doi:10.1007/s40572-015-0072-x. PMID 26452675.
  36. ^ Vu, Tuan V.; Harrison, Roy M. (May 8, 2019). "Chemical and Physical Properties of Indoor Aerosols". In Harrison, R. M.; Hester, R. E. (eds.). Indoor Air Pollution. The Royal Society of Chemistry (published 2019). ISBN 978-1-78801-803-6.
  37. ^ Abdullahi, Karimatu L.; Delgado-Saborit, Juana Maria; Harrison, Roy M. (February 13, 2013). "Emissions and indoor concentrations of particulate matter and its specific chemical components from cooking: A review". Atmospheric Environment. 71: 260–294. Bibcode:2013AtmEn..71..260A. doi:10.1016/j.atmosenv.2013.01.061. Archived from the original on May 21, 2023. Retrieved April 11, 2024.
  38. ^ Patel, Sameer; Sankhyan, Sumit; Boedicker, Erin K.; DeCarlo, Peter F.; Farmer, Delphine K.; Goldstein, Allen H.; Katz, Erin F.; Nazaroff, William W; Tian, Yilin; Vanhanen, Joonas; Vance, Marina E. (June 16, 2020). "Indoor Particulate Matter during HOMEChem: Concentrations, Size Distributions, and Exposures". Environmental Science & Technology. 54 (12): 7107–7116. Bibcode:2020EnST...54.7107P. doi:10.1021/acs.est.0c00740. ISSN 0013-936X. PMID 32391692. Archived from the original on April 28, 2023. Retrieved April 11, 2024.
  39. ^ Thangavel, Prakash; Park, Duckshin; Lee, Young-Chul (June 19, 2022). "Recent Insights into Particulate Matter (PM2.5)-Mediated Toxicity in Humans: An Overview". International Journal of Environmental Research and Public Health. 19 (12): 7511. doi:10.3390/ijerph19127511. ISSN 1660-4601. PMC 9223652. PMID 35742761.
  40. ^ You, Bo; Zhou, Wei; Li, Junyao; Li, Zhijie; Sun, Yele (November 4, 2022). "A review of indoor Gaseous organic compounds and human chemical Exposure: Insights from Real-time measurements". Environment International. 170: 107611. Bibcode:2022EnInt.17007611Y. doi:10.1016/j.envint.2022.107611. PMID 36335895.
  41. ^ Weschler, Charles J.; Carslaw, Nicola (March 6, 2018). "Indoor Chemistry". Environmental Science & Technology. 52 (5): 2419–2428. Bibcode:2018EnST...52.2419W. doi:10.1021/acs.est.7b06387. ISSN 0013-936X. PMID 29402076. Archived from the original on November 15, 2023. Retrieved April 11, 2024.
  42. ^ a b Carter, Toby J.; Poppendieck, Dustin G.; Shaw, David; Carslaw, Nicola (January 16, 2023). "A Modelling Study of Indoor Air Chemistry: The Surface Interactions of Ozone and Hydrogen Peroxide". Atmospheric Environment. 297: 119598. Bibcode:2023AtmEn.29719598C. doi:10.1016/j.atmosenv.2023.119598.
  43. ^ Tsai, Wen-Tien (March 26, 2019). "An overview of health hazards of volatile organic compounds regulated as indoor air pollutants". Reviews on Environmental Health. 34 (1): 81–89. doi:10.1515/reveh-2018-0046. PMID 30854833.
  44. ^ "U.S. EPA IAQ – Organic chemicals". Epa.gov. August 5, 2010. Archived from the original on September 9, 2015. Retrieved March 2, 2012.
  45. ^ a b Davies, Helen L.; O'Leary, Catherine; Dillon, Terry; Shaw, David R.; Shaw, Marvin; Mehra, Archit; Phillips, Gavin; Carslaw, Nicola (August 14, 2023). "A measurement and modelling investigation of the indoor air chemistry following cooking activities". Environmental Science: Processes & Impacts. 25 (9): 1532–1548. doi:10.1039/D3EM00167A. ISSN 2050-7887. PMID 37609942.
  46. ^ a b c Harding-Smith, Ellen; Shaw, David R.; Shaw, Marvin; Dillon, Terry J.; Carslaw, Nicola (January 23, 2024). "Does green mean clean? Volatile organic emissions from regular versus green cleaning products". Environmental Science: Processes & Impacts. 26 (2): 436–450. doi:10.1039/D3EM00439B. ISSN 2050-7887. PMID 38258874.
  47. ^ Lebel, Eric D.; Michanowicz, Drew R.; Bilsback, Kelsey R.; Hill, Lee Ann L.; Goldman, Jackson S. W.; Domen, Jeremy K.; Jaeger, Jessie M.; Ruiz, Angélica; Shonkoff, Seth B. C. (November 15, 2022). "Composition, Emissions, and Air Quality Impacts of Hazardous Air Pollutants in Unburned Natural Gas from Residential Stoves in California". Environmental Science & Technology. 56 (22): 15828–15838. Bibcode:2022EnST...5615828L. doi:10.1021/acs.est.2c02581. ISSN 0013-936X. PMC 9671046. PMID 36263944.
  48. ^ "Volatile Organic Compounds' Impact on Indoor Air Quality". United States Environmental Protection Agency. August 18, 2014. Retrieved May 23, 2024.
  49. ^ "About VOCs". January 21, 2013. Archived from the original on January 21, 2013. Retrieved September 16, 2019.
  50. ^ Oanh, Nguyen Thi Kim; Hung, Yung-Tse (2005). "Indoor Air Pollution Control". Advanced Air and Noise Pollution Control. Handbook of Environmental Engineering. Vol. 2. pp. 237–272. doi:10.1007/978-1-59259-779-6_7. ISBN 978-1-58829-359-6.
  51. ^ "Emicode". Eurofins.com. Archived from the original on September 24, 2015. Retrieved March 2, 2012.
  52. ^ "M1". Eurofins.com. Archived from the original on September 24, 2015. Retrieved March 2, 2012.
  53. ^ "Blue Angel". Eurofins.com. Archived from the original on September 24, 2015. Retrieved March 2, 2012.
  54. ^ "Indoor Air Comfort". Indoor Air Comfort. Archived from the original on February 1, 2011. Retrieved March 2, 2012.
  55. ^ "CDPH Section 01350". Eurofins.com. Archived from the original on September 24, 2015. Retrieved March 2, 2012.
  56. ^ a b "Smelly Moldy Houses". Archived from the original on December 15, 2021. Retrieved August 2, 2014.
  57. ^ Meruva, N. K.; Penn, J. M.; Farthing, D. E. (November 2004). "Rapid identification of microbial VOCs from tobacco molds using closed-loop stripping and gas chromatography/time-of-flight mass spectrometry". J Ind Microbiol Biotechnol. 31 (10): 482–8. doi:10.1007/s10295-004-0175-0. PMID 15517467. S2CID 32543591.
  58. ^ "Atmospheric carbon dioxide passes 400 ppm everywhere". Physics Today (6): 8170. 2016. Bibcode:2016PhT..2016f8170.. doi:10.1063/pt.5.029904.
  59. ^ Xie Y, Li Y, Feng Y, Cheng W, Wang Y (April 2022). "Inhalable microplastics prevails in air: Exploring the size detection limit". Environ Int. 162: 107151. Bibcode:2022EnInt.16207151X. doi:10.1016/j.envint.2022.107151. PMID 35228011.
  60. ^ Liu C, Li J, Zhang Y, Wang L, Deng J, Gao Y, Yu L, Zhang J, Sun H (July 2019). "Widespread distribution of PET and PC microplastics in dust in urban China and their estimated human exposure". Environ Int. 128: 116–124. Bibcode:2019EnInt.128..116L. doi:10.1016/j.envint.2019.04.024. PMID 31039519.
  61. ^ Yuk, Hyeonseong; Jo, Ho Hyeon; Nam, Jihee; Kim, Young Uk; Kim, Sumin (2022). "Microplastic: A particulate matter(PM) generated by deterioration of building materials". Journal of Hazardous Materials. 437. Elsevier BV: 129290. Bibcode:2022JHzM..43729290Y. doi:10.1016/j.jhazmat.2022.129290. ISSN 0304-3894. PMID 35753297.
  62. ^ Eberhard, Tiffany; Casillas, Gaston; Zarus, Gregory M.; Barr, Dana Boyd (January 6, 2024). "Systematic review of microplastics and nanoplastics in indoor and outdoor air: identifying a framework and data needs for quantifying human inhalation exposures" (PDF). Journal of Exposure Science & Environmental Epidemiology. 34 (2). Springer Science and Business Media LLC: 185–196. doi:10.1038/s41370-023-00634-x. ISSN 1559-0631. Retrieved December 19, 2024. MPs have been found in water and soil, and recent research is exposing the vast amount of them in ambient and indoor air.
  63. ^ Gasperi, Johnny; Wright, Stephanie L.; Dris, Rachid; Collard, France; Mandin, Corinne; Guerrouache, Mohamed; Langlois, Valérie; Kelly, Frank J.; Tassin, Bruno (2018). "Microplastics in air: Are we breathing it in?" (PDF). Current Opinion in Environmental Science & Health. 1: 1–5. Bibcode:2018COESH...1....1G. doi:10.1016/j.coesh.2017.10.002. S2CID 133750509. Archived (PDF) from the original on March 6, 2020. Retrieved July 11, 2019.
  64. ^ Prasittisopin, Lapyote; Ferdous, Wahid; Kamchoom, Viroon (2023). "Microplastics in construction and built environment". Developments in the Built Environment. 15. Elsevier BV. doi:10.1016/j.dibe.2023.100188. ISSN 2666-1659.
  65. ^ Galloway, Nanette LoBiondo (September 13, 2024). "Ventnor introduces ordinance to control microplastics contamination". DownBeach. Retrieved October 2, 2024.
  66. ^ Weschler, Charles J. (December 2000). "Ozone in Indoor Environments: Concentration and Chemistry: Ozone in Indoor Environments". Indoor Air. 10 (4): 269–288. doi:10.1034/j.1600-0668.2000.010004269.x. PMID 11089331. Archived from the original on April 15, 2024. Retrieved April 11, 2024.
  67. ^ Weschler, Charles J.; Nazaroff, William W (February 22, 2023). "Human skin oil: a major ozone reactant indoors". Environmental Science: Atmospheres. 3 (4): 640–661. doi:10.1039/D3EA00008G. ISSN 2634-3606. Archived from the original on April 15, 2024. Retrieved April 11, 2024.
  68. ^ Kumar, Prashant; Kalaiarasan, Gopinath; Porter, Alexandra E.; Pinna, Alessandra; KÅ‚osowski, MichaÅ‚ M.; Demokritou, Philip; Chung, Kian Fan; Pain, Christopher; Arvind, D. K.; Arcucci, Rossella; Adcock, Ian M.; Dilliway, Claire (February 20, 2021). "An overview of methods of fine and ultrafine particle collection for physicochemical characterisation and toxicity assessments". Science of the Total Environment. 756: 143553. Bibcode:2021ScTEn.75643553K. doi:10.1016/j.scitotenv.2020.143553. hdl:10044/1/84518. PMID 33239200. S2CID 227176222.
  69. ^ Apte, M. G.; Buchanan, I. S. H.; Mendell, M. J. (April 2008). "Outdoor ozone and building-related symptoms in the BASE study". Indoor Air. 18 (2): 156–170. Bibcode:2008InAir..18..156A. doi:10.1111/j.1600-0668.2008.00521.x. PMID 18333994.
  70. ^ "Eight-hour Average Ozone Concentrations | Ground-level Ozone | New England | US EPA". United States Environmental Protection Agency. Archived from the original on December 15, 2021. Retrieved September 16, 2019.
  71. ^ a b c Park, J. H.; Cox-Ganser, J. M. (2011). "Meta-Mold exposure and respiratory health in damp indoor environments". Frontiers in Bioscience. 3 (2): 757–771. doi:10.2741/e284. PMID 21196349.
  72. ^ "CDC – Mold – General Information – Facts About Mold and Dampness". December 4, 2018. Archived from the original on December 16, 2019. Retrieved June 23, 2017.
  73. ^ Singh, Dr Jagjit; Singh, Jagjit, eds. (1994). Building Mycology (1 ed.). Taylor & Francis. doi:10.4324/9780203974735. ISBN 978-1-135-82462-4.
  74. ^ a b Clarke, J.A; Johnstone, C.M; Kelly, N.J; McLean, R.C; anderson, J.A; Rowan, N.J; Smith, J.E (January 20, 1999). "A technique for the prediction of the conditions leading to mould growth in buildings". Building and Environment. 34 (4): 515–521. Bibcode:1999BuEnv..34..515C. doi:10.1016/S0360-1323(98)00023-7. Archived from the original on October 26, 2022. Retrieved April 10, 2024.
  75. ^ Vereecken, Evy; Roels, Staf (November 15, 2011). "Review of mould prediction models and their influence on mould risk evaluation". Building and Environment. 51: 296–310. doi:10.1016/j.buildenv.2011.11.003. Archived from the original on March 2, 2024. Retrieved April 11, 2024.
  76. ^ BS 5250:2021 - Management of moisture in buildings. Code of practice. British Standards Institution (BSI). October 31, 2021. ISBN 978-0-539-18975-9.
  77. ^ Madgwick, Della; Wood, Hannah (August 8, 2016). "The problem of clothes drying in new homes in the UK". Structural Survey. 34 (4/5): 320–330. doi:10.1108/SS-10-2015-0048. ISSN 0263-080X. Archived from the original on May 7, 2021. Retrieved April 11, 2024.
  78. ^ May, Neil; McGilligan, Charles; Ucci, Marcella (2017). "Health and Moisture in Buildings" (PDF). UK Centre for Moisture in Buildings. Archived (PDF) from the original on April 11, 2024. Retrieved April 11, 2024.
  79. ^ "Understanding and addressing the health risks of damp and mould in the home". GOV.UK. September 7, 2023. Archived from the original on April 10, 2024. Retrieved April 11, 2024.
  80. ^ Clark, Sierra N.; Lam, Holly C. Y.; Goode, Emma-Jane; Marczylo, Emma L.; Exley, Karen S.; Dimitroulopoulou, Sani (August 2, 2023). "The Burden of Respiratory Disease from Formaldehyde, Damp and Mould in English Housing". Environments. 10 (8): 136. doi:10.3390/environments10080136. ISSN 2076-3298.
  81. ^ Microbiology of the Indoor Environment Archived July 23, 2011, at the Wayback Machine, microbe.net
  82. ^ http://www.info.gov.hk/info/sars/pdf/amoy_e.pdf
  83. ^ https://www.info.gov.hk/info/sars/graphics/amoyannex.jpg
  84. ^ "Progress in Global Surveillance and Response Capacity 10 Years after Severe Acute Respiratory Syndrome". environmental contamination with SARS CoV RNA was identified on the carpet in front of the index case-patient's room and 3 nearby rooms (and on their door frames but not inside the rooms) and in the air intake vents near the centrally located elevators ... secondary infections occurred not in guest rooms but in the common areas of the ninth floor, such as the corridor or elevator hall. These areas could have been contaminated through body fluids (e.g., vomitus, expectorated sputum), respiratory droplets, or suspended small-particle aerosols generated by the index case-patient; other guests were then infected by fomites or aerosols while passing through these same areas. Efficient spread of SARS CoV through small-particle aerosols was observed in several superspreading events in health care settings, during an airplane flight, and in an apartment complex (12–14,16–19). This process of environmental contamination that generated infectious aerosols likely best explains the pattern of disease transmission at the Hotel Metropole.
  85. ^ Azuma, Kenichi; Kagi, Naoki; Yanagi, U.; Osawa, Haruki (December 2018). "Effects of low-level inhalation exposure to carbon dioxide in indoor environments: A short review on human health and psychomotor performance". Environment International. 121 (Pt 1): 51–56. Bibcode:2018EnInt.121...51A. doi:10.1016/j.envint.2018.08.059. PMID 30172928.
  86. ^ Du, Bowen; Tandoc, Michael (June 19, 2020). "Indoor CO2 concentrations and cognitive function: A critical review". International Journal of Indoor Environment and Health. 30 (6): 1067–1082. Bibcode:2020InAir..30.1067D. doi:10.1111/ina.12706. PMID 32557862. S2CID 219915861.
  87. ^ Fan, Yuejie; Cao, Xiaodong; Zhang, Jie; Lai, Dayi; Pang, Liping (June 1, 2023). "Short-term exposure to indoor carbon dioxide and cognitive task performance: A systematic review and meta-analysis". Building and Environment. 237: 110331. Bibcode:2023BuEnv.23710331F. doi:10.1016/j.buildenv.2023.110331.
  88. ^ a b Lowther, Scott D.; Dimitroulopoulou, Sani; Foxall, Kerry; Shrubsole, Clive; Cheek, Emily; Gadeberg, Britta; Sepai, Ovnair (November 16, 2021). "Low Level Carbon Dioxide Indoors—A Pollution Indicator or a Pollutant? A Health-Based Perspective". Environments. 8 (11): 125. doi:10.3390/environments8110125. ISSN 2076-3298.
  89. ^ Persily, Andrew (July 2022). "Development and application of an indoor carbon dioxide metric". Indoor Air. 32 (7): e13059. doi:10.1111/ina.13059. PMID 35904382.
  90. ^ "Indoor Environmental Quality: HVAC Management | NIOSH | CDC". www.cdc.gov. February 25, 2022. Archived from the original on April 1, 2022. Retrieved April 1, 2022.
  91. ^ Indoor Environmental Quality: Building Ventilation Archived January 20, 2022, at the Wayback Machine. National Institute for Occupational Safety and Health. Accessed October 8, 2008.
  92. ^ "SAMHE - Schools' Air quality Monitoring for Health and Education". samhe.org.uk. Archived from the original on March 18, 2024. Retrieved March 18, 2024.
  93. ^ "Document Display | NEPIS | US EPA". nepis.epa.gov. Archived from the original on November 16, 2023. Retrieved October 19, 2023.
  94. ^ Zeeb & Shannoun 2009, p. 3.
  95. ^ C.Michael Hogan and Sjaak Slanina. 2010, Air pollution. Encyclopedia of Earth Archived October 12, 2006, at the Wayback Machine. eds. Sidney Draggan and Cutler Cleveland. National Council for Science and the Environment. Washington DC
  96. ^ "Radon Mitigation Methods". Radon Solution—Raising Radon Awareness. Archived from the original on December 15, 2008. Retrieved December 2, 2008.
  97. ^ Zeeb & Shannoun 2009, p. [page needed].
  98. ^ "Basic radon facts" (PDF). US Environmental Protection Agency. Archived (PDF) from the original on January 13, 2022. Retrieved September 18, 2018. Public Domain This article incorporates text from this source, which is in the public domain.
  99. ^ "Radon Action Level and Target Level". UKradon. Archived from the original on March 18, 2024. Retrieved March 18, 2024.
  100. ^ "Radon Zone Map (with State Information)". U.S. Environmental Protection Agency. Archived from the original on April 1, 2023. Retrieved April 10, 2024.
  101. ^ "UK maps of radon". UKradon. Archived from the original on March 7, 2024. Retrieved April 10, 2024.
  102. ^ "Radon map of Australia". Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). Archived from the original on March 20, 2024. Retrieved April 10, 2024.
  103. ^ "Climate Change 2021: The Physical Science Basis". Intergovernmental Panel on Climate Change. Archived (PDF) from the original on May 26, 2023. Retrieved April 15, 2024.
  104. ^ Chen, Guochao; Qiu, Minghao; Wang, Peng; Zhang, Yuqiang; Shindell, Drew; Zhang, Hongliang (July 19, 2024). "Continuous wildfires threaten public and ecosystem health under climate change across continents". Frontiers of Environmental Science & Engineering. 18 (10). doi:10.1007/s11783-024-1890-6. ISSN 2095-2201.
  105. ^ Gherasim, Alina; Lee, Alison G.; Bernstein, Jonathan A. (November 14, 2023). "Impact of Climate Change on Indoor Air Quality". Immunology and Allergy Clinics of North America. 44 (1): 55–73. doi:10.1016/j.iac.2023.09.001. PMID 37973260. Archived from the original on November 15, 2023. Retrieved April 15, 2024.
  106. ^ Lacressonnière, Gwendoline; Watson, Laura; Gauss, Michael; Engardt, Magnuz; Andersson, Camilla; Beekmann, Matthias; Colette, Augustin; Foret, Gilles; Josse, Béatrice; Marécal, Virginie; Nyiri, Agnes; Siour, Guillaume; Sobolowski, Stefan; Vautard, Robert (February 1, 2017). "Particulate matter air pollution in Europe in a +2 °C warming world". Atmospheric Environment. 154: 129–140. Bibcode:2017AtmEn.154..129L. doi:10.1016/j.atmosenv.2017.01.037. Archived from the original on November 17, 2023. Retrieved April 15, 2024.
  107. ^ Lee, J; Lewis, A; Monks, P; Jacob, M; Hamilton, J; Hopkins, J; Watson, N; Saxton, J; Ennis, C; Carpenter, L (September 26, 2006). "Ozone photochemistry and elevated isoprene during the UK heatwave of august 2003". Atmospheric Environment. 40 (39): 7598–7613. Bibcode:2006AtmEn..40.7598L. doi:10.1016/j.atmosenv.2006.06.057. Archived from the original on October 26, 2022. Retrieved April 15, 2024.
  108. ^ Salthammer, Tunga; Schieweck, Alexandra; Gu, Jianwei; Ameri, Shaghayegh; Uhde, Erik (August 7, 2018). "Future trends in ambient air pollution and climate in Germany – Implications for the indoor environment". Building and Environment. 143: 661–670. Bibcode:2018BuEnv.143..661S. doi:10.1016/j.buildenv.2018.07.050.
  109. ^ Zhong, L.; Lee, C.-S.; Haghighat, F. (December 1, 2016). "Indoor ozone and climate change". Sustainable Cities and Society. 28: 466–472. doi:10.1016/j.scs.2016.08.020. Archived from the original on November 28, 2022. Retrieved April 15, 2024.
  110. ^ Zhao, Jiangyue; Uhde, Erik; Salthammer, Tunga; Antretter, Florian; Shaw, David; Carslaw, Nicola; Schieweck, Alexandra (December 9, 2023). "Long-term prediction of the effects of climate change on indoor climate and air quality". Environmental Research. 243: 117804. doi:10.1016/j.envres.2023.117804. PMID 38042519.
  111. ^ Niculita-Hirzel, Hélène (March 16, 2022). "Latest Trends in Pollutant Accumulations at Threatening Levels in Energy-Efficient Residential Buildings with and without Mechanical Ventilation: A Review". International Journal of Environmental Research and Public Health. 19 (6): 3538. doi:10.3390/ijerph19063538. ISSN 1660-4601. PMC 8951331. PMID 35329223.
  112. ^ UK Health Security Agency (2024) [1 September 2012]. "Chapter 5: Impact of climate change policies on indoor environmental quality and health in UK housing". Health Effects of Climate Change (HECC) in the UK: 2023 report (published January 15, 2024).
  113. ^ World Health Organization, ed. (2010). Who guidelines for indoor air quality: selected pollutants. Copenhagen: WHO. ISBN 978-92-890-0213-4. OCLC 696099951.
  114. ^ "Air quality: UK guidelines for volatile organic compounds in indoor spaces". Public Health England. September 13, 2019. Retrieved April 17, 2024.
  115. ^ "Home - IEQ Guidelines". ieqguidelines.org. Retrieved April 17, 2024.
  116. ^ Toyinbo, Oluyemi; Hägerhed, Linda; Dimitroulopoulou, Sani; Dudzinska, Marzenna; Emmerich, Steven; Hemming, David; Park, Ju-Hyeong; Haverinen-Shaughnessy, Ulla; the Scientific Technical Committee 34 of the International Society of Indoor Air Quality, Climate (April 19, 2022). "Open database for international and national indoor environmental quality guidelines". Indoor Air. 32 (4): e13028. doi:10.1111/ina.13028. ISSN 0905-6947. PMC 11099937. PMID 35481936.cite journal: CS1 maint: numeric names: authors list (link)
  117. ^ Dimitroulopoulou, Sani; DudziÅ„ska, Marzenna R.; Gunnarsen, Lars; Hägerhed, Linda; Maula, Henna; Singh, Raja; Toyinbo, Oluyemi; Haverinen-Shaughnessy, Ulla (August 4, 2023). "Indoor air quality guidelines from across the world: An appraisal considering energy saving, health, productivity, and comfort". Environment International. 178: 108127. Bibcode:2023EnInt.17808127D. doi:10.1016/j.envint.2023.108127. PMID 37544267.
  118. ^ Pitarma, Rui; Marques, Gonçalo; Ferreira, Bárbara Roque (February 2017). "Monitoring Indoor Air Quality for Enhanced Occupational Health". Journal of Medical Systems. 41 (2): 23. doi:10.1007/s10916-016-0667-2. PMID 28000117. S2CID 7372403.
  119. ^ Wyon, D. P. (August 2004). "The effects of indoor air quality on performance and productivity: The effects of IAQ on performance and productivity". Indoor Air. 14: 92–101. doi:10.1111/j.1600-0668.2004.00278.x. PMID 15330777.
  120. ^ Son, Young Joo; Pope, Zachary C.; Pantelic, Jovan (September 2023). "Perceived air quality and satisfaction during implementation of an automated indoor air quality monitoring and control system". Building and Environment. 243: 110713. Bibcode:2023BuEnv.24310713S. doi:10.1016/j.buildenv.2023.110713.
  121. ^ IAQM (2021). Indoor Air Quality Guidance: Assessment, Monitoring, Modelling and Mitigation (PDF) (Version 0.1 ed.). London: Institute of Air Quality Management.
  122. ^ a b Institute for Occupational Safety and Health of the German Social Accident Insurance. "Indoor workplaces – Recommended procedure for the investigation of working environment". Archived from the original on November 3, 2021. Retrieved June 10, 2020.
  123. ^ "Climate Change: Atmospheric Carbon Dioxide | NOAA Climate.gov". www.climate.gov. April 9, 2024. Retrieved May 6, 2024.
  124. ^ "Ventilation to reduce the spread of respiratory infections, including COVID-19". GOV.UK. August 2, 2022. Archived from the original on January 18, 2024. Retrieved April 15, 2024.
  125. ^ Dela Cruz, Majbrit; Christensen, Jan H.; Thomsen, Jane Dyrhauge; Müller, Renate (December 2014). "Can ornamental potted plants remove volatile organic compounds from indoor air? — a review". Environmental Science and Pollution Research. 21 (24): 13909–13928. Bibcode:2014ESPR...2113909D. doi:10.1007/s11356-014-3240-x. PMID 25056742. S2CID 207272189.
  126. ^ Cummings, Bryan E.; Waring, Michael S. (March 2020). "Potted plants do not improve indoor air quality: a review and analysis of reported VOC removal efficiencies". Journal of Exposure Science & Environmental Epidemiology. 30 (2): 253–261. Bibcode:2020JESEE..30..253C. doi:10.1038/s41370-019-0175-9. PMID 31695112. S2CID 207911697.
  127. ^ Wolverton, B. C.; Wolverton, J. D. (1996). "Interior plants: their influence on airborne microbes inside energy-efficient buildings". Journal of the Mississippi Academy of Sciences. 41 (2): 100–105.
  128. ^ US EPA, OAR (July 16, 2013). "Mold". US EPA. Archived from the original on May 18, 2020. Retrieved September 16, 2019.
  129. ^ Institute of Medicine (US) Committee on Damp Indoor Spaces and Health (2004). Damp Indoor Spaces and Health. National Academies Press. ISBN 978-0-309-09193-0. PMID 25009878. Archived from the original on January 19, 2023. Retrieved March 30, 2024.[page needed]
  130. ^ "Indoor Environmental Quality". Washington, DC: US National Institute for Occupational Safety and Health. Archived from the original on December 3, 2013. Retrieved May 17, 2013.
  131. ^ Lewis, Alastair C; Allan, James; Carslaw, David; Carruthers, David; Fuller, Gary; Harrison, Roy; Heal, Mathew; Nemitz, Eiko; Reeves, Claire (2022). Indoor Air Quality (PDF) (Report). Air Quality Expert Group. doi:10.5281/zenodo.6523605. Archived (PDF) from the original on June 5, 2023. Retrieved April 15, 2024.
  132. ^ "Isiaq.Org". International Society of Indoor Air Quality and Climate. Archived from the original on January 21, 2022. Retrieved March 2, 2012.

Sources

[edit]
Monographs
Articles, radio segments, web pages

Further reading

[edit]
[edit]

 

 

There are various types of air conditioners. Popular examples include: Window-mounted air conditioner (Suriname, 1955); Ceiling-mounted cassette air conditioner (China, 2023); Wall-mounted air conditioner (Japan, 2020); Ceiling-mounted console (Also called ceiling suspended) air conditioner (China, 2023); and portable air conditioner (Vatican City, 2018).

Air conditioning, often abbreviated as A/C (US) or air con (UK),[1] is the process of removing heat from an enclosed space to achieve a more comfortable interior temperature and in some cases also controlling the humidity of internal air. Air conditioning can be achieved using a mechanical 'air conditioner' or by other methods, including passive cooling and ventilative cooling.[2][3] Air conditioning is a member of a family of systems and techniques that provide heating, ventilation, and air conditioning (HVAC).[4] Heat pumps are similar in many ways to air conditioners, but use a reversing valve to allow them both to heat and to cool an enclosed space.[5]

Air conditioners, which typically use vapor-compression refrigeration, range in size from small units used in vehicles or single rooms to massive units that can cool large buildings.[6] Air source heat pumps, which can be used for heating as well as cooling, are becoming increasingly common in cooler climates.

Air conditioners can reduce mortality rates due to higher temperature.[7] According to the International Energy Agency (IEA) 1.6 billion air conditioning units were used globally in 2016.[8] The United Nations called for the technology to be made more sustainable to mitigate climate change and for the use of alternatives, like passive cooling, evaporative cooling, selective shading, windcatchers, and better thermal insulation.

History

[edit]

Air conditioning dates back to prehistory.[9] Double-walled living quarters, with a gap between the two walls to encourage air flow, were found in the ancient city of Hamoukar, in modern Syria.[10] Ancient Egyptian buildings also used a wide variety of passive air-conditioning techniques.[11] These became widespread from the Iberian Peninsula through North Africa, the Middle East, and Northern India.[12]

Passive techniques remained widespread until the 20th century when they fell out of fashion and were replaced by powered air conditioning. Using information from engineering studies of traditional buildings, passive techniques are being revived and modified for 21st-century architectural designs.[13][12]

An array of air conditioner condenser units outside a commercial office building

Air conditioners allow the building's indoor environment to remain relatively constant, largely independent of changes in external weather conditions and internal heat loads. They also enable deep plan buildings to be created and have allowed people to live comfortably in hotter parts of the world.[14]

Development

[edit]

Preceding discoveries

[edit]

In 1558, Giambattista della Porta described a method of chilling ice to temperatures far below its freezing point by mixing it with potassium nitrate (then called "nitre") in his popular science book Natural Magic.[15][16][17] In 1620, Cornelis Drebbel demonstrated "Turning Summer into Winter" for James I of England, chilling part of the Great Hall of Westminster Abbey with an apparatus of troughs and vats.[18] Drebbel's contemporary Francis Bacon, like della Porta a believer in science communication, may not have been present at the demonstration, but in a book published later the same year, he described it as "experiment of artificial freezing" and said that "Nitre (or rather its spirit) is very cold, and hence nitre or salt when added to snow or ice intensifies the cold of the latter, the nitre by adding to its cold, but the salt by supplying activity to the cold of the snow."[15]

In 1758, Benjamin Franklin and John Hadley, a chemistry professor at the University of Cambridge, conducted experiments applying the principle of evaporation as a means to cool an object rapidly. Franklin and Hadley confirmed that the evaporation of highly volatile liquids (such as alcohol and ether) could be used to drive down the temperature of an object past the freezing point of water. They experimented with the bulb of a mercury-in-glass thermometer as their object. They used a bellows to speed up the evaporation. They lowered the temperature of the thermometer bulb down to −14 °C (7 °F) while the ambient temperature was 18 °C (64 °F). Franklin noted that soon after they passed the freezing point of water 0 °C (32 °F), a thin film of ice formed on the surface of the thermometer's bulb and that the ice mass was about 6 mm (14 in) thick when they stopped the experiment upon reaching −14 °C (7 °F). Franklin concluded: "From this experiment, one may see the possibility of freezing a man to death on a warm summer's day."[19]

The 19th century included many developments in compression technology. In 1820, English scientist and inventor Michael Faraday discovered that compressing and liquefying ammonia could chill air when the liquefied ammonia was allowed to evaporate.[20] In 1842, Florida physician John Gorrie used compressor technology to create ice, which he used to cool air for his patients in his hospital in Apalachicola, Florida. He hoped to eventually use his ice-making machine to regulate the temperature of buildings.[20][21] He envisioned centralized air conditioning that could cool entire cities. Gorrie was granted a patent in 1851,[22] but following the death of his main backer, he was not able to realize his invention.[23] In 1851, James Harrison created the first mechanical ice-making machine in Geelong, Australia, and was granted a patent for an ether vapor-compression refrigeration system in 1855 that produced three tons of ice per day.[24] In 1860, Harrison established a second ice company. He later entered the debate over competing against the American advantage of ice-refrigerated beef sales to the United Kingdom.[24]

First devices

[edit]
Willis Carrier, who is credited with building the first modern electrical air conditioning unit

Electricity made the development of effective units possible. In 1901, American inventor Willis H. Carrier built what is considered the first modern electrical air conditioning unit.[25][26][27][28] In 1902, he installed his first air-conditioning system, in the Sackett-Wilhelms Lithographing & Publishing Company in Brooklyn, New York.[29] His invention controlled both the temperature and humidity, which helped maintain consistent paper dimensions and ink alignment at the printing plant. Later, together with six other employees, Carrier formed The Carrier Air Conditioning Company of America, a business that in 2020 employed 53,000 people and was valued at $18.6 billion.[30][31]

In 1906, Stuart W. Cramer of Charlotte, North Carolina, was exploring ways to add moisture to the air in his textile mill. Cramer coined the term "air conditioning" in a patent claim which he filed that year, where he suggested that air conditioning was analogous to "water conditioning", then a well-known process for making textiles easier to process.[32] He combined moisture with ventilation to "condition" and change the air in the factories; thus, controlling the humidity that is necessary in textile plants. Willis Carrier adopted the term and incorporated it into the name of his company.[33]

Domestic air conditioning soon took off. In 1914, the first domestic air conditioning was installed in Minneapolis in the home of Charles Gilbert Gates. It is, however, possible that the considerable device (c. 2.1 m × 1.8 m × 6.1 m; 7 ft × 6 ft × 20 ft) was never used, as the house remained uninhabited[20] (Gates had already died in October 1913.)

In 1931, H.H. Schultz and J.Q. Sherman developed what would become the most common type of individual room air conditioner: one designed to sit on a window ledge. The units went on sale in 1932 at US$10,000 to $50,000 (the equivalent of $200,000 to $1,200,000 in 2024.)[20] A year later, the first air conditioning systems for cars were offered for sale.[34] Chrysler Motors introduced the first practical semi-portable air conditioning unit in 1935,[35] and Packard became the first automobile manufacturer to offer an air conditioning unit in its cars in 1939.[36]

Further development

[edit]

Innovations in the latter half of the 20th century allowed more ubiquitous air conditioner use. In 1945, Robert Sherman of Lynn, Massachusetts, invented a portable, in-window air conditioner that cooled, heated, humidified, dehumidified, and filtered the air.[37] The first inverter air conditioners were released in 1980–1981.[38][39]

In 1954, Ned Cole, a 1939 architecture graduate from the University of Texas at Austin, developed the first experimental "suburb" with inbuilt air conditioning in each house. 22 homes were developed on a flat, treeless track in northwest Austin, Texas, and the community was christened the 'Austin Air-Conditioned Village.' The residents were subjected to a year-long study of the effects of air conditioning led by the nation’s premier air conditioning companies, builders, and social scientists. In addition, researchers from UT’s Health Service and Psychology Department studied the effects on the "artificially cooled humans." One of the more amusing discoveries was that each family reported being troubled with scorpions, the leading theory being that scorpions sought cool, shady places. Other reported changes in lifestyle were that mothers baked more, families ate heavier foods, and they were more apt to choose hot drinks.[40][41]

Air conditioner adoption tends to increase above around $10,000 annual household income in warmer areas.[42] Global GDP growth explains around 85% of increased air condition adoption by 2050, while the remaining 15% can be explained by climate change.[42]

As of 2016 an estimated 1.6 billion air conditioning units were used worldwide, with over half of them in China and USA, and a total cooling capacity of 11,675 gigawatts.[8][43] The International Energy Agency predicted in 2018 that the number of air conditioning units would grow to around 4 billion units by 2050 and that the total cooling capacity would grow to around 23,000 GW, with the biggest increases in India and China.[8] Between 1995 and 2004, the proportion of urban households in China with air conditioners increased from 8% to 70%.[44] As of 2015, nearly 100 million homes, or about 87% of US households, had air conditioning systems.[45] In 2019, it was estimated that 90% of new single-family homes constructed in the US included air conditioning (ranging from 99% in the South to 62% in the West).[46][47]

Operation

[edit]

Operating principles

[edit]
A simple stylized diagram of the refrigeration cycle: 1) condensing coil, 2) expansion valve, 3) evaporator coil, 4) compressor

Cooling in traditional air conditioner systems is accomplished using the vapor-compression cycle, which uses a refrigerant's forced circulation and phase change between gas and liquid to transfer heat.[48][49] The vapor-compression cycle can occur within a unitary, or packaged piece of equipment; or within a chiller that is connected to terminal cooling equipment (such as a fan coil unit in an air handler) on its evaporator side and heat rejection equipment such as a cooling tower on its condenser side. An air source heat pump shares many components with an air conditioning system, but includes a reversing valve, which allows the unit to be used to heat as well as cool a space.[50]

Air conditioning equipment will reduce the absolute humidity of the air processed by the system if the surface of the evaporator coil is significantly cooler than the dew point of the surrounding air. An air conditioner designed for an occupied space will typically achieve a 30% to 60% relative humidity in the occupied space.[51]

Most modern air-conditioning systems feature a dehumidification cycle during which the compressor runs. At the same time, the fan is slowed to reduce the evaporator temperature and condense more water. A dehumidifier uses the same refrigeration cycle but incorporates both the evaporator and the condenser into the same air path; the air first passes over the evaporator coil, where it is cooled[52] and dehumidified before passing over the condenser coil, where it is warmed again before it is released back into the room.[citation needed]

Free cooling can sometimes be selected when the external air is cooler than the internal air. Therefore, the compressor does not need to be used, resulting in high cooling efficiencies for these times. This may also be combined with seasonal thermal energy storage.[53]

Heating

[edit]

Some air conditioning systems can reverse the refrigeration cycle and act as an air source heat pump, thus heating instead of cooling the indoor environment. They are also commonly referred to as "reverse cycle air conditioners". The heat pump is significantly more energy-efficient than electric resistance heating, because it moves energy from air or groundwater to the heated space and the heat from purchased electrical energy. When the heat pump is in heating mode, the indoor evaporator coil switches roles and becomes the condenser coil, producing heat. The outdoor condenser unit also switches roles to serve as the evaporator and discharges cold air (colder than the ambient outdoor air).

Most air source heat pumps become less efficient in outdoor temperatures lower than 4 °C or 40 °F.[54] This is partly because ice forms on the outdoor unit's heat exchanger coil, which blocks air flow over the coil. To compensate for this, the heat pump system must temporarily switch back into the regular air conditioning mode to switch the outdoor evaporator coil back to the condenser coil, to heat up and defrost. Therefore, some heat pump systems will have electric resistance heating in the indoor air path that is activated only in this mode to compensate for the temporary indoor air cooling, which would otherwise be uncomfortable in the winter.

Newer models have improved cold-weather performance, with efficient heating capacity down to −14 °F (−26 °C).[55][54][56] However, there is always a chance that the humidity that condenses on the heat exchanger of the outdoor unit could freeze, even in models that have improved cold-weather performance, requiring a defrosting cycle to be performed.

The icing problem becomes much more severe with lower outdoor temperatures, so heat pumps are sometimes installed in tandem with a more conventional form of heating, such as an electrical heater, a natural gas, heating oil, or wood-burning fireplace or central heating, which is used instead of or in addition to the heat pump during harsher winter temperatures. In this case, the heat pump is used efficiently during milder temperatures, and the system is switched to the conventional heat source when the outdoor temperature is lower.

Performance

[edit]

The coefficient of performance (COP) of an air conditioning system is a ratio of useful heating or cooling provided to the work required.[57][58] Higher COPs equate to lower operating costs. The COP usually exceeds 1; however, the exact value is highly dependent on operating conditions, especially absolute temperature and relative temperature between sink and system, and is often graphed or averaged against expected conditions.[59] Air conditioner equipment power in the U.S. is often described in terms of "tons of refrigeration", with each approximately equal to the cooling power of one short ton (2,000 pounds (910 kg) of ice melting in a 24-hour period. The value is equal to 12,000 BTUIT per hour, or 3,517 watts.[60] Residential central air systems are usually from 1 to 5 tons (3.5 to 18 kW) in capacity.[citation needed]

The efficiency of air conditioners is often rated by the seasonal energy efficiency ratio (SEER), which is defined by the Air Conditioning, Heating and Refrigeration Institute in its 2008 standard AHRI 210/240, Performance Rating of Unitary Air-Conditioning and Air-Source Heat Pump Equipment.[61] A similar standard is the European seasonal energy efficiency ratio (ESEER).[citation needed]

Efficiency is strongly affected by the humidity of the air to be cooled. Dehumidifying the air before attempting to cool it can reduce subsequent cooling costs by as much as 90 percent. Thus, reducing dehumidifying costs can materially affect overall air conditioning costs.[62]

Control system

[edit]

Wireless remote control

[edit]
A wireless remote controller
The infrared transmitting LED on the remote
The infrared receiver on the air conditioner

This type of controller uses an infrared LED to relay commands from a remote control to the air conditioner. The output of the infrared LED (like that of any infrared remote) is invisible to the human eye because its wavelength is beyond the range of visible light (940 nm). This system is commonly used on mini-split air conditioners because it is simple and portable. Some window and ducted central air conditioners uses it as well.

Wired controller

[edit]
Several wired controllers (Indonesia, 2024)

A wired controller, also called a "wired thermostat," is a device that controls an air conditioner by switching heating or cooling on or off. It uses different sensors to measure temperatures and actuate control operations. Mechanical thermostats commonly use bimetallic strips, converting a temperature change into mechanical displacement, to actuate control of the air conditioner. Electronic thermostats, instead, use a thermistor or other semiconductor sensor, processing temperature change as electronic signals to control the air conditioner.

These controllers are usually used in hotel rooms because they are permanently installed into a wall and hard-wired directly into the air conditioner unit, eliminating the need for batteries.

Types

[edit]
 
Types Typical Capacity* Air supply Mounting Typical application
Mini-split small – large Direct Wall Residential
Window very small – small Direct Window Residential
Portable very small – small Direct / Ducted Floor Residential, remote areas
Ducted (individual) small – very large Ducted Ceiling Residential, commercial
Ducted (central) medium – very large Ducted Ceiling Residential, commercial
Ceiling suspended medium – large Direct Ceiling Commercial
Cassette medium – large Direct / Ducted Ceiling Commercial
Floor standing medium – large Direct / Ducted Floor Commercial
Packaged very large Direct / Ducted Floor Commercial
Packaged RTU (Rooftop Unit) very large Ducted Rooftop Commercial

* where the typical capacity is in kilowatt as follows:

  • very small: <1.5 kW
  • small: 1.5–3.5 kW
  • medium: 4.2–7.1 kW
  • large: 7.2–14 kW
  • very large: >14 kW

Mini-split and multi-split systems

[edit]
Evaporator, indoor unit, or terminal, side of a ductless split-type air conditioner

Ductless systems (often mini-split, though there are now ducted mini-split) typically supply conditioned and heated air to a single or a few rooms of a building, without ducts and in a decentralized manner.[63] Multi-zone or multi-split systems are a common application of ductless systems and allow up to eight rooms (zones or locations) to be conditioned independently from each other, each with its indoor unit and simultaneously from a single outdoor unit.

The first mini-split system was sold in 1961 by Toshiba in Japan, and the first wall-mounted mini-split air conditioner was sold in 1968 in Japan by Mitsubishi Electric, where small home sizes motivated their development. The Mitsubishi model was the first air conditioner with a cross-flow fan.[64][65][66] In 1969, the first mini-split air conditioner was sold in the US.[67] Multi-zone ductless systems were invented by Daikin in 1973, and variable refrigerant flow systems (which can be thought of as larger multi-split systems) were also invented by Daikin in 1982. Both were first sold in Japan.[68] Variable refrigerant flow systems when compared with central plant cooling from an air handler, eliminate the need for large cool air ducts, air handlers, and chillers; instead cool refrigerant is transported through much smaller pipes to the indoor units in the spaces to be conditioned, thus allowing for less space above dropped ceilings and a lower structural impact, while also allowing for more individual and independent temperature control of spaces. The outdoor and indoor units can be spread across the building.[69] Variable refrigerant flow indoor units can also be turned off individually in unused spaces.[citation needed] The lower start-up power of VRF's DC inverter compressors and their inherent DC power requirements also allow VRF solar-powered heat pumps to be run using DC-providing solar panels.

Ducted central systems

[edit]

Split-system central air conditioners consist of two heat exchangers, an outside unit (the condenser) from which heat is rejected to the environment and an internal heat exchanger (the evaporator, or Fan Coil Unit, FCU) with the piped refrigerant being circulated between the two. The FCU is then connected to the spaces to be cooled by ventilation ducts.[70] Floor standing air conditioners are similar to this type of air conditioner but sit within spaces that need cooling.

Central plant cooling

[edit]
Industrial air conditioners on top of the shopping mall Passage in Linz, Austria

Large central cooling plants may use intermediate coolant such as chilled water pumped into air handlers or fan coil units near or in the spaces to be cooled which then duct or deliver cold air into the spaces to be conditioned, rather than ducting cold air directly to these spaces from the plant, which is not done due to the low density and heat capacity of air, which would require impractically large ducts. The chilled water is cooled by chillers in the plant, which uses a refrigeration cycle to cool water, often transferring its heat to the atmosphere even in liquid-cooled chillers through the use of cooling towers. Chillers may be air- or liquid-cooled.[71][72]

Portable units

[edit]

A portable system has an indoor unit on wheels connected to an outdoor unit via flexible pipes, similar to a permanently fixed installed unit (such as a ductless split air conditioner).

Hose systems, which can be monoblock or air-to-air, are vented to the outside via air ducts. The monoblock type collects the water in a bucket or tray and stops when full. The air-to-air type re-evaporates the water, discharges it through the ducted hose, and can run continuously. Many but not all portable units draw indoor air and expel it outdoors through a single duct, negatively impacting their overall cooling efficiency.

Many portable air conditioners come with heat as well as a dehumidification function.[73]

Window unit and packaged terminal

[edit]
Through-the-wall PTAC units, University Motor Inn, Philadelphia

The packaged terminal air conditioner (PTAC), through-the-wall, and window air conditioners are similar. These units are installed on a window frame or on a wall opening. The unit usually has an internal partition separating its indoor and outdoor sides, which contain the unit's condenser and evaporator, respectively. PTAC systems may be adapted to provide heating in cold weather, either directly by using an electric strip, gas, or other heaters, or by reversing the refrigerant flow to heat the interior and draw heat from the exterior air, converting the air conditioner into a heat pump. They may be installed in a wall opening with the help of a special sleeve on the wall and a custom grill that is flush with the wall and window air conditioners can also be installed in a window, but without a custom grill.[74]

Packaged air conditioner

[edit]

Packaged air conditioners (also known as self-contained units)[75][76] are central systems that integrate into a single housing all the components of a split central system, and deliver air, possibly through ducts, to the spaces to be cooled. Depending on their construction they may be outdoors or indoors, on roofs (rooftop units),[77][78] draw the air to be conditioned from inside or outside a building and be water or air-cooled. Often, outdoor units are air-cooled while indoor units are liquid-cooled using a cooling tower.[70][79][80][81][82][83]

Types of compressors

[edit]
 
Compressor types Common applications Typical capacity Efficiency Durability Repairability
Reciprocating Refrigerator, Walk-in freezer, portable air conditioners small – large very low (small capacity)

medium (large capacity)

very low medium
Rotary vane Residential mini splits small low low easy
Scroll Commercial and central systems, VRF medium medium medium easy
Rotary screw Commercial chiller medium – large medium medium hard
Centrifugal Commercial chiller very large medium high hard
Maglev Centrifugal Commercial chiller very large high very high very hard

Reciprocating

[edit]

This compressor consists of a crankcase, crankshaft, piston rod, piston, piston ring, cylinder head and valves. [citation needed]

Scroll

[edit]

This compressor uses two interleaving scrolls to compress the refrigerant.[84] it consists of one fixed and one orbiting scrolls. This type of compressor is more efficient because it has 70 percent less moving parts than a reciprocating compressor. [citation needed]

Screw

[edit]

This compressor use two very closely meshing spiral rotors to compress the gas. The gas enters at the suction side and moves through the threads as the screws rotate. The meshing rotors force the gas through the compressor, and the gas exits at the end of the screws. The working area is the inter-lobe volume between the male and female rotors. It is larger at the intake end, and decreases along the length of the rotors until the exhaust port. This change in volume is the compression. [citation needed]

Capacity modulation technologies

[edit]

There are several ways to modulate the cooling capacity in refrigeration or air conditioning and heating systems. The most common in air conditioning are: on-off cycling, hot gas bypass, use or not of liquid injection, manifold configurations of multiple compressors, mechanical modulation (also called digital), and inverter technology. [citation needed]

Hot gas bypass

[edit]

Hot gas bypass involves injecting a quantity of gas from discharge to the suction side. The compressor will keep operating at the same speed, but due to the bypass, the refrigerant mass flow circulating with the system is reduced, and thus the cooling capacity. This naturally causes the compressor to run uselessly during the periods when the bypass is operating. The turn down capacity varies between 0 and 100%.[85]

Manifold configurations

[edit]

Several compressors can be installed in the system to provide the peak cooling capacity. Each compressor can run or not in order to stage the cooling capacity of the unit. The turn down capacity is either 0/33/66 or 100% for a trio configuration and either 0/50 or 100% for a tandem.[citation needed]

Mechanically modulated compressor

[edit]

This internal mechanical capacity modulation is based on periodic compression process with a control valve, the two scroll set move apart stopping the compression for a given time period. This method varies refrigerant flow by changing the average time of compression, but not the actual speed of the motor. Despite an excellent turndown ratio – from 10 to 100% of the cooling capacity, mechanically modulated scrolls have high energy consumption as the motor continuously runs.[citation needed]

Variable-speed compressor

[edit]

This system uses a variable-frequency drive (also called an Inverter) to control the speed of the compressor. The refrigerant flow rate is changed by the change in the speed of the compressor. The turn down ratio depends on the system configuration and manufacturer. It modulates from 15 or 25% up to 100% at full capacity with a single inverter from 12 to 100% with a hybrid tandem. This method is the most efficient way to modulate an air conditioner's capacity. It is up to 58% more efficient than a fixed speed system.[citation needed]

Impact

[edit]

Health effects

[edit]
Rooftop condenser unit fitted on top of an Osaka Municipal Subway 10 series subway carriage. Air conditioning has become increasingly prevalent on public transport vehicles as a form of climate control, and to ensure passenger comfort and drivers' occupational safety and health.

In hot weather, air conditioning can prevent heat stroke, dehydration due to excessive sweating, electrolyte imbalance, kidney failure, and other issues due to hyperthermia.[8][86] Heat waves are the most lethal type of weather phenomenon in the United States.[87][88] A 2020 study found that areas with lower use of air conditioning correlated with higher rates of heat-related mortality and hospitalizations.[89] The August 2003 France heatwave resulted in approximately 15,000 deaths, where 80% of the victims were over 75 years old. In response, the French government required all retirement homes to have at least one air-conditioned room at 25 °C (77 °F) per floor during heatwaves.[8]

Air conditioning (including filtration, humidification, cooling and disinfection) can be used to provide a clean, safe, hypoallergenic atmosphere in hospital operating rooms and other environments where proper atmosphere is critical to patient safety and well-being. It is sometimes recommended for home use by people with allergies, especially mold.[90][91] However, poorly maintained water cooling towers can promote the growth and spread of microorganisms such as Legionella pneumophila, the infectious agent responsible for Legionnaires' disease. As long as the cooling tower is kept clean (usually by means of a chlorine treatment), these health hazards can be avoided or reduced. The state of New York has codified requirements for registration, maintenance, and testing of cooling towers to protect against Legionella.[92]

Economic effects

[edit]

First designed to benefit targeted industries such as the press as well as large factories, the invention quickly spread to public agencies and administrations with studies with claims of increased productivity close to 24% in places equipped with air conditioning.[93]

Air conditioning caused various shifts in demography, notably that of the United States starting from the 1970s. In the US, the birth rate was lower in the spring than during other seasons until the 1970s but this difference then declined since then.[94] As of 2007, the Sun Belt contained 30% of the total US population while it was inhabited by 24% of Americans at the beginning of the 20th century.[95] Moreover, the summer mortality rate in the US, which had been higher in regions subject to a heat wave during the summer, also evened out.[7]

The spread of the use of air conditioning acts as a main driver for the growth of global demand of electricity.[96] According to a 2018 report from the International Energy Agency (IEA), it was revealed that the energy consumption for cooling in the United States, involving 328 million Americans, surpasses the combined energy consumption of 4.4 billion people in Africa, Latin America, the Middle East, and Asia (excluding China).[8] A 2020 survey found that an estimated 88% of all US households use AC, increasing to 93% when solely looking at homes built between 2010 and 2020.[97]

Environmental effects

[edit]
Air conditioner farm in the facade of a building in Singapore

Space cooling including air conditioning accounted globally for 2021 terawatt-hours of energy usage in 2016 with around 99% in the form of electricity, according to a 2018 report on air-conditioning efficiency by the International Energy Agency.[8] The report predicts an increase of electricity usage due to space cooling to around 6200 TWh by 2050,[8][98] and that with the progress currently seen, greenhouse gas emissions attributable to space cooling will double: 1,135 million tons (2016) to 2,070 million tons.[8] There is some push to increase the energy efficiency of air conditioners. United Nations Environment Programme (UNEP) and the IEA found that if air conditioners could be twice as effective as now, 460 billion tons of GHG could be cut over 40 years.[99] The UNEP and IEA also recommended legislation to decrease the use of hydrofluorocarbons, better building insulation, and more sustainable temperature-controlled food supply chains going forward.[99]

Refrigerants have also caused and continue to cause serious environmental issues, including ozone depletion and climate change, as several countries have not yet ratified the Kigali Amendment to reduce the consumption and production of hydrofluorocarbons.[100] CFCs and HCFCs refrigerants such as R-12 and R-22, respectively, used within air conditioners have caused damage to the ozone layer,[101] and hydrofluorocarbon refrigerants such as R-410A and R-404A, which were designed to replace CFCs and HCFCs, are instead exacerbating climate change.[102] Both issues happen due to the venting of refrigerant to the atmosphere, such as during repairs. HFO refrigerants, used in some if not most new equipment, solve both issues with an ozone damage potential (ODP) of zero and a much lower global warming potential (GWP) in the single or double digits vs. the three or four digits of hydrofluorocarbons.[103]

Hydrofluorocarbons would have raised global temperatures by around 0.3–0.5 °C (0.5–0.9 °F) by 2100 without the Kigali Amendment. With the Kigali Amendment, the increase of global temperatures by 2100 due to hydrofluorocarbons is predicted to be around 0.06 °C (0.1 °F).[104]

Alternatives to continual air conditioning include passive cooling, passive solar cooling, natural ventilation, operating shades to reduce solar gain, using trees, architectural shades, windows (and using window coatings) to reduce solar gain.[citation needed]

Social effects

[edit]

Socioeconomic groups with a household income below around $10,000 tend to have a low air conditioning adoption,[42] which worsens heat-related mortality.[7] The lack of cooling can be hazardous, as areas with lower use of air conditioning correlate with higher rates of heat-related mortality and hospitalizations.[89] Premature mortality in NYC is projected to grow between 47% and 95% in 30 years, with lower-income and vulnerable populations most at risk.[89] Studies on the correlation between heat-related mortality and hospitalizations and living in low socioeconomic locations can be traced in Phoenix, Arizona,[105] Hong Kong,[106] China,[106] Japan,[107] and Italy.[108][109] Additionally, costs concerning health care can act as another barrier, as the lack of private health insurance during a 2009 heat wave in Australia, was associated with heat-related hospitalization.[109]

Disparities in socioeconomic status and access to air conditioning are connected by some to institutionalized racism, which leads to the association of specific marginalized communities with lower economic status, poorer health, residing in hotter neighborhoods, engaging in physically demanding labor, and experiencing limited access to cooling technologies such as air conditioning.[109] A study overlooking Chicago, Illinois, Detroit, and Michigan found that black households were half as likely to have central air conditioning units when compared to their white counterparts.[110] Especially in cities, Redlining creates heat islands, increasing temperatures in certain parts of the city.[109] This is due to materials heat-absorbing building materials and pavements and lack of vegetation and shade coverage.[111] There have been initiatives that provide cooling solutions to low-income communities, such as public cooling spaces.[8][111]

Other techniques

[edit]

Buildings designed with passive air conditioning are generally less expensive to construct and maintain than buildings with conventional HVAC systems with lower energy demands.[112] While tens of air changes per hour, and cooling of tens of degrees, can be achieved with passive methods, site-specific microclimate must be taken into account, complicating building design.[12]

Many techniques can be used to increase comfort and reduce the temperature in buildings. These include evaporative cooling, selective shading, wind, thermal convection, and heat storage.[113]

Passive ventilation

[edit]
The ventilation system of a regular earthship
Dogtrot houses are designed to maximise natural ventilation.
A roof turbine ventilator, colloquially known as a 'Whirly Bird' is an application of wind driven ventilation.

Passive ventilation is the process of supplying air to and removing air from an indoor space without using mechanical systems. It refers to the flow of external air to an indoor space as a result of pressure differences arising from natural forces.

There are two types of natural ventilation occurring in buildings: wind driven ventilation and buoyancy-driven ventilation. Wind driven ventilation arises from the different pressures created by wind around a building or structure, and openings being formed on the perimeter which then permit flow through the building. Buoyancy-driven ventilation occurs as a result of the directional buoyancy force that results from temperature differences between the interior and exterior.[114]

Since the internal heat gains which create temperature differences between the interior and exterior are created by natural processes, including the heat from people, and wind effects are variable, naturally ventilated buildings are sometimes called "breathing buildings".

Passive cooling

[edit]
 
A traditional Iranian solar cooling design using a wind tower

Passive cooling is a building design approach that focuses on heat gain control and heat dissipation in a building in order to improve the indoor thermal comfort with low or no energy consumption.[115][116] This approach works either by preventing heat from entering the interior (heat gain prevention) or by removing heat from the building (natural cooling).[117]

Natural cooling utilizes on-site energy, available from the natural environment, combined with the architectural design of building components (e.g. building envelope), rather than mechanical systems to dissipate heat.[118] Therefore, natural cooling depends not only on the architectural design of the building but on how the site's natural resources are used as heat sinks (i.e. everything that absorbs or dissipates heat). Examples of on-site heat sinks are the upper atmosphere (night sky), the outdoor air (wind), and the earth/soil.

Passive cooling is an important tool for design of buildings for climate change adaptation – reducing dependency on energy-intensive air conditioning in warming environments.[119][120]
A pair of short windcatchers (malqaf) used in traditional architecture; wind is forced down on the windward side and leaves on the leeward side (cross-ventilation). In the absence of wind, the circulation can be driven with evaporative cooling in the inlet (which is also designed to catch dust). In the center, a shuksheika (roof lantern vent), used to shade the qa'a below while allowing hot air rise out of it (stack effect).[11]

Daytime radiative cooling

[edit]
Passive daytime radiative cooling (PDRC) surfaces are high in solar reflectance and heat emittance, cooling with zero energy use or pollution.[121]

Passive daytime radiative cooling (PDRC) surfaces reflect incoming solar radiation and heat back into outer space through the infrared window for cooling during the daytime. Daytime radiative cooling became possible with the ability to suppress solar heating using photonic structures, which emerged through a study by Raman et al. (2014).[122] PDRCs can come in a variety of forms, including paint coatings and films, that are designed to be high in solar reflectance and thermal emittance.[121][123]

PDRC applications on building roofs and envelopes have demonstrated significant decreases in energy consumption and costs.[123] In suburban single-family residential areas, PDRC application on roofs can potentially lower energy costs by 26% to 46%.[124] PDRCs are predicted to show a market size of ~$27 billion for indoor space cooling by 2025 and have undergone a surge in research and development since the 2010s.[125][126]

Fans

[edit]

Hand fans have existed since prehistory. Large human-powered fans built into buildings include the punkah.

The 2nd-century Chinese inventor Ding Huan of the Han dynasty invented a rotary fan for air conditioning, with seven wheels 3 m (10 ft) in diameter and manually powered by prisoners.[127]: 99, 151, 233  In 747, Emperor Xuanzong (r. 712–762) of the Tang dynasty (618–907) had the Cool Hall (Liang Dian 涼殿) built in the imperial palace, which the Tang Yulin describes as having water-powered fan wheels for air conditioning as well as rising jet streams of water from fountains. During the subsequent Song dynasty (960–1279), written sources mentioned the air conditioning rotary fan as even more widely used.[127]: 134, 151 

Thermal buffering

[edit]

In areas that are cold at night or in winter, heat storage is used. Heat may be stored in earth or masonry; air is drawn past the masonry to heat or cool it.[13]

In areas that are below freezing at night in winter, snow and ice can be collected and stored in ice houses for later use in cooling.[13] This technique is over 3,700 years old in the Middle East.[128] Harvesting outdoor ice during winter and transporting and storing for use in summer was practiced by wealthy Europeans in the early 1600s,[15] and became popular in Europe and the Americas towards the end of the 1600s.[129] This practice was replaced by mechanical compression-cycle icemakers.

Evaporative cooling

[edit]
An evaporative cooler

In dry, hot climates, the evaporative cooling effect may be used by placing water at the air intake, such that the draft draws air over water and then into the house. For this reason, it is sometimes said that the fountain, in the architecture of hot, arid climates, is like the fireplace in the architecture of cold climates.[11] Evaporative cooling also makes the air more humid, which can be beneficial in a dry desert climate.[130]

Evaporative coolers tend to feel as if they are not working during times of high humidity, when there is not much dry air with which the coolers can work to make the air as cool as possible for dwelling occupants. Unlike other types of air conditioners, evaporative coolers rely on the outside air to be channeled through cooler pads that cool the air before it reaches the inside of a house through its air duct system; this cooled outside air must be allowed to push the warmer air within the house out through an exhaust opening such as an open door or window.[131]

See also

[edit]

References

[edit]
  1. ^ "Air Con". Cambridge Dictionary. Archived from the original on May 3, 2022. Retrieved January 6, 2023.
  2. ^ Dissertation Abstracts International: The humanities and social sciences. A. University Microfilms. 2005. p. 3600.
  3. ^ 1993 ASHRAE Handbook: Fundamentals. ASHRAE. 1993. ISBN 978-0-910110-97-6.
  4. ^ Enteria, Napoleon; Sawachi, Takao; Saito, Kiyoshi (January 31, 2023). Variable Refrigerant Flow Systems: Advances and Applications of VRF. Springer Nature. p. 46. ISBN 978-981-19-6833-4.
  5. ^ Agencies, United States Congress House Committee on Appropriations Subcommittee on Dept of the Interior and Related (1988). Department of the Interior and Related Agencies Appropriations for 1989: Testimony of public witnesses, energy programs, Institute of Museum Services, National Endowment for the Arts, National Endowment for the Humanities. U.S. Government Printing Office. p. 629.
  6. ^ "Earth Tubes: Providing the freshest possible air to your building". Earth Rangers Centre for Sustainable Technology Showcase. Archived from the original on January 28, 2021. Retrieved May 12, 2021.
  7. ^ a b c Barreca, Alan; Clay, Karen; Deschenes, Olivier; Greenstone, Michael; Shapiro, Joseph S. (February 2016). "Adapting to Climate Change: The Remarkable Decline in the US Temperature-Mortality Relationship over the Twentieth Century". Journal of Political Economy. 124 (1): 105–159. doi:10.1086/684582.
  8. ^ a b c d e f g h i j International Energy Agency (May 15, 2018). The Future of Cooling - Opportunities for energy-efficient air conditioning (PDF) (Report). Archived (PDF) from the original on June 26, 2024. Retrieved July 1, 2024.
  9. ^ Laub, Julian M. (1963). Air Conditioning & Heating Practice. Holt, Rinehart and Winston. p. 367. ISBN 978-0-03-011225-6.
  10. ^ "Air-conditioning found at 'oldest city in the world'". The Independent. June 24, 2000. Archived from the original on December 8, 2023. Retrieved December 9, 2023.
  11. ^ a b c Mohamed, Mady A.A. (January 2010). Lehmann, S.; Waer, H.A.; Al-Qawasmi, J. (eds.). Traditional Ways of Dealing with Climate in Egypt. The Seventh International Conference of Sustainable Architecture and Urban Development (SAUD 2010). Amman, Jordan: The Center for the Study of Architecture in Arab Region (CSAAR Press). pp. 247–266. Archived from the original on May 13, 2021. Retrieved May 12, 2021.
  12. ^ a b c Ford, Brian (September 2001). "Passive downdraught evaporative cooling: principles and practice". Architectural Research Quarterly. 5 (3): 271–280. doi:10.1017/S1359135501001312.
  13. ^ a b c Attia, Shady; Herde, André de (June 22–24, 2009). Designing the Malqaf for Summer Cooling in Low-Rise Housing, an Experimental Study. 26th Conference on Passive and Low Energy Architecture (PLEA2009). Quebec City. Archived from the original on May 13, 2021. Retrieved May 12, 2021 – via ResearchGate.
  14. ^ "Heating, Ventilation and Air-Conditioning Systems, Part of Indoor Air Quality Design Tools for Schools". US EPA. October 17, 2014. Archived from the original on July 5, 2022. Retrieved July 5, 2022.
  15. ^ a b c Shachtman, Tom (1999). "Winter in Summer". Absolute zero and the conquest of cold. Boston: Houghton Mifflin Harcourt. ISBN 978-0395938881. OCLC 421754998. Archived from the original on May 13, 2021. Retrieved May 12, 2021.
  16. ^ Porta, Giambattista Della (1584). Magiae naturalis (PDF). London. LCCN 09023451. Archived (PDF) from the original on May 13, 2021. Retrieved May 12, 2021. In our method I shall observe what our ancestors have said; then I shall show by my own experience, whether they be true or false
  17. ^ Beck, Leonard D. (October 1974). "Things Magical in the collections of the Rare Book and Special Collections Division" (PDF). Library of Congress Quarterly Journal. 31: 208–234. Archived (PDF) from the original on March 24, 2021. Retrieved May 12, 2021.
  18. ^ Laszlo, Pierre (2001). Salt: Grain of Life. Columbia University Press. p. 117. ISBN 978-0231121989. OCLC 785781471. Cornelius Drebbel air conditioning.
  19. ^ Franklin, Benjamin (June 17, 1758). "The Montgomery Family: An historical and photographic perspective". Letter to John Lining. Archived from the original on February 25, 2021. Retrieved May 12, 2021.
  20. ^ a b c d Green, Amanda (January 1, 2015). "The Cool History of the Air Conditioner". Popular Mechanics. Archived from the original on April 10, 2021. Retrieved May 12, 2021.
  21. ^ "John Gorrie". Encyclopædia Britannica. September 29, 2020. Archived from the original on March 13, 2021. Retrieved May 12, 2021.
  22. ^ Gorrie, John "Improved process for the artificial production of ice" U.S. Patent no. 8080 (Issued: May 6, 1851).
  23. ^ Wright, E. Lynne (2009). It Happened in Florida: Remarkable Events That Shaped History. Rowman & Littlefield. pp. 13–. ISBN 978-0762761692.
  24. ^ a b Bruce-Wallace, L. G. (1966). "Harrison, James (1816–1893)". Australian Dictionary of Biography. Vol. 1. Canberra: National Centre of Biography, Australian National University. ISBN 978-0-522-84459-7. ISSN 1833-7538. OCLC 70677943. Retrieved May 12, 2021.
  25. ^ Palermo, Elizabeth (May 1, 2014). "Who Invented Air Conditioning?". livescience.com. Archived from the original on January 16, 2021. Retrieved May 12, 2021.
  26. ^ Varrasi, John (June 6, 2011). "Global Cooling: The History of Air Conditioning". American Society of Mechanical Engineers. Archived from the original on March 8, 2021. Retrieved May 12, 2021.
  27. ^ Simha, R. V. (February 2012). "Willis H Carrier". Resonance. 17 (2): 117–138. doi:10.1007/s12045-012-0014-y. ISSN 0971-8044. S2CID 116582893.
  28. ^ Gulledge III, Charles; Knight, Dennis (February 11, 2016). "Heating, Ventilating, Air-Conditioning, And Refrigerating Engineering". National Institute of Building Sciences. Archived from the original on April 20, 2021. Retrieved May 12, 2021. Though he did not actually invent air-conditioning nor did he take the first documented scientific approach to applying it, Willis Carrier is credited with integrating the scientific method, engineering, and business of this developing technology and creating the industry we know today as air-conditioning.
  29. ^ "Willis Carrier – 1876–1902". Carrier Global. Archived from the original on February 27, 2021. Retrieved May 12, 2021.
  30. ^ "Carrier Reports First Quarter 2020 Earnings". Carrier Global (Press release). May 8, 2020. Archived from the original on January 24, 2021. Retrieved May 12, 2021.
  31. ^ "Carrier Becomes Independent, Publicly Traded Company, Begins Trading on New York Stock Exchange". Carrier Global (Press release). April 3, 2020. Archived from the original on February 25, 2021. Retrieved May 12, 2021.
  32. ^ Cramer, Stuart W. "Humidifying and air conditioning apparatus" U.S. Patent no. 852,823 (filed: April 18, 1906; issued: May 7, 1907).
    • See also: Cramer, Stuart W. (1906) "Recent development in air conditioning" in: Proceedings of the Tenth Annual Convention of the American Cotton Manufacturers Association Held at Asheville, North Carolina May 16–17, 1906. Charlotte, North Carolina, USA: Queen City Publishing Co. pp. 182-211.
  33. ^ US patent US808897A, Carrier, Willis H., "Apparatus for treating air", published January 2, 1906, issued January 2, 1906 and Buffalo Forge Company "No. 808,897 Patented Jan. 2, 1906: H. W. Carrier: Apparatus for Treating Air" (PDF). Archived (PDF) from the original on December 5, 2019. Retrieved May 12, 2021.
  34. ^ "First Air-Conditioned Auto". Popular Science. Vol. 123, no. 5. November 1933. p. 30. ISSN 0161-7370. Archived from the original on April 26, 2021. Retrieved May 12, 2021.
  35. ^ "Room-size air conditioner fits under window sill". Popular Mechanics. Vol. 63, no. 6. June 1935. p. 885. ISSN 0032-4558. Archived from the original on November 22, 2016. Retrieved May 12, 2021.
  36. ^ "Michigan Fast Facts and Trivia". 50states.com. Archived from the original on June 18, 2017. Retrieved May 12, 2021.
  37. ^ US patent US2433960A, Sherman, Robert S., "Air conditioning apparatus", published January 6, 1948, issued January 6, 1948 
  38. ^ "IEEE milestones (39) Inverter Air Conditioners, 1980–1981" (PDF). March 2021. Archived (PDF) from the original on January 21, 2024. Retrieved February 9, 2024.
  39. ^ "Inverter Air Conditioners, 1980–1981 IEEE Milestone Celebration Ceremony" (PDF). March 16, 2021. Archived (PDF) from the original on January 21, 2024. Retrieved February 9, 2024.
  40. ^ Seale, Avrel (August 7, 2023). "Texas alumnus and his alma mater central to air-conditioned homes". UT News. Retrieved November 13, 2024.
  41. ^ "Air Conditioned Village". Atlas Obscura. Retrieved November 13, 2024.
  42. ^ a b c Davis, Lucas; Gertler, Paul; Jarvis, Stephen; Wolfram, Catherine (July 2021). "Air conditioning and global inequality". Global Environmental Change. 69: 102299. Bibcode:2021GEC....6902299D. doi:10.1016/j.gloenvcha.2021.102299.
  43. ^ Pierre-Louis, Kendra (May 15, 2018). "The World Wants Air-Conditioning. That Could Warm the World". The New York Times. Archived from the original on February 16, 2021. Retrieved May 12, 2021.
  44. ^ Carroll, Rory (October 26, 2015). "How America became addicted to air conditioning". The Guardian. Los Angeles. Archived from the original on March 13, 2021. Retrieved May 12, 2021.
  45. ^ Lester, Paul (July 20, 2015). "History of Air Conditioning". United States Department of Energy. Archived from the original on June 5, 2020. Retrieved May 12, 2021.
  46. ^ Cornish, Cheryl; Cooper, Stephen; Jenkins, Salima. Characteristics of New Housing (Report). United States Census Bureau. Archived from the original on April 11, 2021. Retrieved May 12, 2021.
  47. ^ "Central Air Conditioning Buying Guide". Consumer Reports. March 3, 2021. Archived from the original on May 9, 2021. Retrieved May 12, 2021.
  48. ^ Petchers, Neil (2003). Combined Heating, Cooling & Power Handbook: Technologies & Applications : an Integrated Approach to Energy Resource Optimization. The Fairmont Press. p. 737. ISBN 978-0-88173-433-1.
  49. ^ Krarti, Moncef (December 1, 2020). Energy Audit of Building Systems: An Engineering Approach, Third Edition. CRC Press. p. 370. ISBN 978-1-000-25967-4.
  50. ^ "What is a Reversing Valve". Samsung India. Archived from the original on February 22, 2019. Retrieved May 12, 2021.
  51. ^ "Humidity and Comfort" (PDF). DriSteem. Archived from the original (PDF) on May 16, 2018. Retrieved May 12, 2021.
  52. ^ Perryman, Oliver (April 19, 2021). "Dehumidifier vs Air Conditioning". Dehumidifier Critic. Archived from the original on May 13, 2021. Retrieved May 12, 2021.
  53. ^ Snijders, Aart L. (July 30, 2008). "Aquifer Thermal Energy Storage (ATES) Technology Development and Major Applications in Europe" (PDF). Toronto and Region Conservation Authority. Arnhem: IFTech International. Archived (PDF) from the original on March 8, 2021. Retrieved May 12, 2021.
  54. ^ a b "Cold Climate Air Source Heat Pump" (PDF). Minnesota Department of Commerce, Division of Energy Resources. Archived (PDF) from the original on January 2, 2022. Retrieved March 29, 2022.
  55. ^ "Even in Frigid Temperatures, Air-Source Heat Pumps Keep Homes Warm From Alaska Coast to U.S. Mass Market". nrel.gov. Archived from the original on April 10, 2022. Retrieved March 29, 2022.
  56. ^ "Heat Pumps: A Practical Solution for Cold Climates". RMI. December 10, 2020. Archived from the original on March 31, 2022. Retrieved March 28, 2022.
  57. ^ "TEM Instruction Sheet" (PDF). TE Technology. March 14, 2012. Archived from the original (PDF) on January 24, 2013. Retrieved May 12, 2021.
  58. ^ "Coefficient of Performance (COP) heat pumps". Grundfos. November 18, 2020. Archived from the original on May 3, 2021. Retrieved May 12, 2021.
  59. ^ "Unpotted HP-199-1.4-0.8 at a hot-side temperature of 25 °C" (PDF). TE Technology. Archived from the original (PDF) on January 7, 2009. Retrieved February 9, 2024.
  60. ^ Newell, David B.; Tiesinga, Eite, eds. (August 2019). The International System of Units (SI) (PDF). National Institute of Standards and Technology. doi:10.6028/NIST.SP.330-2019. Archived (PDF) from the original on April 22, 2021. Retrieved May 13, 2021.
  61. ^ ANSI/AHRI 210/240-2008: 2008 Standard for Performance Rating of Unitary Air-Conditioning & Air-Source Heat Pump Equipment (PDF). Air Conditioning, Heating and Refrigeration Institute. 2012. Archived from the original on March 29, 2018. Retrieved May 13, 2021.
  62. ^ Baraniuk, Chris. "Cutting-Edge Technology Could Massively Reduce the Amount of Energy Used for Air Conditioning". Wired. ISSN 1059-1028. Retrieved July 18, 2024.
  63. ^ "M-Series Contractor Guide" (PDF). Mitsubishipro.com. p. 19. Archived (PDF) from the original on March 18, 2021. Retrieved May 12, 2021.
  64. ^ "エアコンの歴史とヒミツ | 調べよう家電と省エネ | キッズ版 省エネ家電 de スマートライフ(一般財団法人 家電製品協会) 学ぼう!スマートライフ". shouene-kaden.net. Archived from the original on September 7, 2022. Retrieved January 21, 2024.
  65. ^ "Air conditioner | History". Toshiba Carrier. April 2016. Archived from the original on March 9, 2021. Retrieved May 12, 2021.
  66. ^ "1920s–1970s | History". Mitsubishi Electric. Archived from the original on March 8, 2021. Retrieved May 12, 2021.
  67. ^ Wagner, Gerry (November 30, 2021). "The Duct Free Zone: History of the Mini Split". HPAC Magazine. Retrieved February 9, 2024.
  68. ^ "History of Daikin Innovation". Daikin. Archived from the original on June 5, 2020. Retrieved May 12, 2021.
  69. ^ Feit, Justin (December 20, 2017). "The Emergence of VRF as a Viable HVAC Option". buildings.com. Archived from the original on December 3, 2020. Retrieved May 12, 2021.
  70. ^ a b "Central Air Conditioning". United States Department of Energy. Archived from the original on January 30, 2021. Retrieved May 12, 2021.
  71. ^ Kreith, Frank; Wang, Shan K.; Norton, Paul (April 20, 2018). Air Conditioning and Refrigeration Engineering. CRC Press. ISBN 978-1-351-46783-4.
  72. ^ Wang, Shan K. (November 7, 2000). Handbook of Air Conditioning and Refrigeration. McGraw-Hill Education. ISBN 978-0-07-068167-5.
  73. ^ Hleborodova, Veronika (August 14, 2018). "Portable Vs Split System Air Conditioning | Pros & Cons". Canstar Blue. Archived from the original on March 9, 2021. Retrieved May 12, 2021.
  74. ^ Kamins, Toni L. (July 15, 2013). "Through-the-Wall Versus PTAC Air Conditioners: A Guide for New Yorkers". Brick Underground. Archived from the original on January 15, 2021. Retrieved May 12, 2021.
  75. ^ "Self-Contained Air Conditioning Systems". Daikin Applied Americas. 2015. Archived from the original on October 30, 2020. Retrieved May 12, 2021.
  76. ^ "LSWU/LSWD Vertical Water-Cooled Self-Contained Unit Engineering Guide" (PDF). Johnson Controls. April 6, 2018. Archived (PDF) from the original on May 13, 2021. Retrieved May 12, 2021.
  77. ^ "Packaged Rooftop Unit" (PDF). Carrier Global. 2016. Archived (PDF) from the original on May 13, 2021. Retrieved May 12, 2021.
  78. ^ "Packaged Rooftop Air Conditioners" (PDF). Trane Technologies. November 2006. Archived (PDF) from the original on May 13, 2021. Retrieved May 12, 2021.
  79. ^ "What is Packaged Air Conditioner? Types of Packged Air Condtioners". Bright Hub Engineering. January 13, 2010. Archived from the original on February 22, 2018. Retrieved May 12, 2021.
  80. ^ Evans, Paul (November 11, 2018). "RTU Rooftop Units explained". The Engineering Mindset. Archived from the original on January 15, 2021. Retrieved May 12, 2021.
  81. ^ "water-cooled – Johnson Supply". studylib.net. 2000. Archived from the original on May 13, 2021. Retrieved May 12, 2021.
  82. ^ "Water Cooled Packaged Air Conditioners" (PDF). Japan: Daikin. May 2, 2003. Archived (PDF) from the original on June 19, 2018. Retrieved May 12, 2021.
  83. ^ "Water Cooled Packaged Unit" (PDF). Daikin. Archived (PDF) from the original on May 13, 2021. Retrieved May 12, 2021.
  84. ^ Lun, Y. H. Venus; Tung, S. L. Dennis (November 13, 2019). Heat Pumps for Sustainable Heating and Cooling. Springer Nature. p. 25. ISBN 978-3-030-31387-6.
  85. ^ Ghanbariannaeeni, Ali; Ghazanfarihashemi, Ghazalehsadat (June 2012). "Bypass Method For Recip Compressor Capacity Control". Pipeline and Gas Journal. 239 (6). Archived from the original on August 12, 2014. Retrieved February 9, 2024.
  86. ^ "Heat Stroke (Hyperthermia)". Harvard Health. January 2, 2019. Archived from the original on January 29, 2021. Retrieved May 13, 2021.
  87. ^ "Weather Related Fatality and Injury Statistics". National Weather Service. 2021. Archived from the original on August 24, 2022. Retrieved August 24, 2022.
  88. ^ "Extreme Weather: A Guide to Surviving Flash Floods, Tornadoes, Hurricanes, Heat Waves, Snowstorms Tsunamis and Other Natural Disasters". Reference Reviews. 26 (8): 41. October 19, 2012. doi:10.1108/09504121211278322. ISSN 0950-4125. Archived from the original on January 21, 2024. Retrieved December 9, 2023.
  89. ^ a b c Gamarro, Harold; Ortiz, Luis; González, Jorge E. (August 1, 2020). "Adapting to Extreme Heat: Social, Atmospheric, and Infrastructure Impacts of Air-Conditioning in Megacities—The Case of New York City". Journal of Engineering for Sustainable Buildings and Cities. 1 (3). doi:10.1115/1.4048175. ISSN 2642-6641. S2CID 222121944.
  90. ^ Spiegelman, Jay; Friedman, Herman; Blumstein, George I. (September 1, 1963). "The effects of central air conditioning on pollen, mold, and bacterial concentrations". Journal of Allergy. 34 (5): 426–431. doi:10.1016/0021-8707(63)90007-8. ISSN 0021-8707. PMID 14066385.
  91. ^ Portnoy, Jay M.; Jara, David (February 1, 2015). "Mold allergy revisited". Annals of Allergy, Asthma & Immunology. 114 (2): 83–89. doi:10.1016/j.anai.2014.10.004. ISSN 1081-1206. PMID 25624128.
  92. ^ "Subpart 4-1 – Cooling Towers". New York Codes, Rules and Regulations. June 7, 2016. Archived from the original on May 13, 2021. Retrieved May 13, 2021.
  93. ^ Nordhaus, William D. (February 10, 2010). "Geography and macroeconomics: New data and new findings". Proceedings of the National Academy of Sciences. 103 (10): 3510–3517. doi:10.1073/pnas.0509842103. ISSN 0027-8424. PMC 1363683. PMID 16473945.
  94. ^ Barreca, Alan; Deschenes, Olivier; Guldi, Melanie (2018). "Maybe next month? Temperature shocks and dynamic adjustments in birth rates". Demography. 55 (4): 1269–1293. doi:10.1007/s13524-018-0690-7. PMC 7457515. PMID 29968058.
  95. ^ Glaeser, Edward L.; Tobio, Kristina (January 2008). "The Rise of the Sunbelt". Southern Economic Journal. 74 (3): 609–643. doi:10.1002/j.2325-8012.2008.tb00856.x.
  96. ^ Sherman, Peter; Lin, Haiyang; McElroy, Michael (2018). "Projected global demand for air conditioning associated with extreme heat and implications for electricity grids in poorer countries". Energy and Buildings. 268: 112198. doi:10.1016/j.enbuild.2022.112198. ISSN 0378-7788. S2CID 248979815.
  97. ^ Air Filters Used in Air Conditioning and General Ventilation Part 1: Methods of Test for Atmospheric Dust Spot Efficiency and Synthetic Dust Weight Arrestance (Withdrawn Standard). British Standards Institution. March 29, 1985. BS 6540-1:1985.
  98. ^ Mutschler, Robin; Rüdisüli, Martin; Heer, Philipp; Eggimann, Sven (April 15, 2021). "Benchmarking cooling and heating energy demands considering climate change, population growth and cooling device uptake". Applied Energy. 288: 116636. Bibcode:2021ApEn..28816636M. doi:10.1016/j.apenergy.2021.116636. ISSN 0306-2619.
  99. ^ a b "Climate-friendly cooling could cut years of Greenhouse Gas Emissions and save US$ trillions: UN". Climate Change and Law Collection. doi:10.1163/9789004322714_cclc_2020-0252-0973.
  100. ^ Gerretsen, Isabelle (December 8, 2020). "How your fridge is heating up the planet". BBC Future. Archived from the original on May 10, 2021. Retrieved May 13, 2021.
  101. ^ Encyclopedia of Energy: Ph-S. Elsevier. 2004. ISBN 978-0121764821.
  102. ^ Corberan, J.M. (2016). "New trends and developments in ground-source heat pumps". Advances in Ground-Source Heat Pump Systems. pp. 359–385. doi:10.1016/B978-0-08-100311-4.00013-3. ISBN 978-0-08-100311-4.
  103. ^ Roselli, Carlo; Sasso, Maurizio (2021). Geothermal Energy Utilization and Technologies 2020. MDPI. ISBN 978-3036507040.
  104. ^ "Cooling Emissions and Policy Synthesis Report: Benefits of cooling efficiency and the Kigali Amendment, United Nations Environment Programme - International Energy Agency, 2020" (PDF).
  105. ^ Harlan, Sharon L.; Declet-Barreto, Juan H.; Stefanov, William L.; Petitti, Diana B. (February 2013). "Neighborhood Effects on Heat Deaths: Social and Environmental Predictors of Vulnerability in Maricopa County, Arizona". Environmental Health Perspectives. 121 (2): 197–204. Bibcode:2013EnvHP.121..197H. doi:10.1289/ehp.1104625. ISSN 0091-6765. PMC 3569676. PMID 23164621.
  106. ^ a b Chan, Emily Ying Yang; Goggins, William B; Kim, Jacqueline Jakyoung; Griffiths, Sian M (April 2012). "A study of intracity variation of temperature-related mortality and socioeconomic status among the Chinese population in Hong Kong". Journal of Epidemiology and Community Health. 66 (4): 322–327. doi:10.1136/jech.2008.085167. ISSN 0143-005X. PMC 3292716. PMID 20974839.
  107. ^ Ng, Chris Fook Sheng; Ueda, Kayo; Takeuchi, Ayano; Nitta, Hiroshi; Konishi, Shoko; Bagrowicz, Rinako; Watanabe, Chiho; Takami, Akinori (2014). "Sociogeographic Variation in the Effects of Heat and Cold on Daily Mortality in Japan". Journal of Epidemiology. 24 (1): 15–24. doi:10.2188/jea.JE20130051. PMC 3872520. PMID 24317342.
  108. ^ Stafoggia, Massimo; Forastiere, Francesco; Agostini, Daniele; Biggeri, Annibale; Bisanti, Luigi; Cadum, Ennio; Caranci, Nicola; de'Donato, Francesca; De Lisio, Sara; De Maria, Moreno; Michelozzi, Paola; Miglio, Rossella; Pandolfi, Paolo; Picciotto, Sally; Rognoni, Magda (2006). "Vulnerability to Heat-Related Mortality: A Multicity, Population-Based, Case-Crossover Analysis". Epidemiology. 17 (3): 315–323. doi:10.1097/01.ede.0000208477.36665.34. ISSN 1044-3983. JSTOR 20486220. PMID 16570026. S2CID 20283342.
  109. ^ a b c d Gronlund, Carina J. (September 2014). "Racial and Socioeconomic Disparities in Heat-Related Health Effects and Their Mechanisms: a Review". Current Epidemiology Reports. 1 (3): 165–173. doi:10.1007/s40471-014-0014-4. PMC 4264980. PMID 25512891.
  110. ^ O'Neill, M. S. (May 11, 2005). "Disparities by Race in Heat-Related Mortality in Four US Cities: The Role of Air Conditioning Prevalence". Journal of Urban Health: Bulletin of the New York Academy of Medicine. 82 (2): 191–197. doi:10.1093/jurban/jti043. PMC 3456567. PMID 15888640.
  111. ^ a b Sampson, Natalie R.; Gronlund, Carina J.; Buxton, Miatta A.; Catalano, Linda; White-Newsome, Jalonne L.; Conlon, Kathryn C.; O’Neill, Marie S.; McCormick, Sabrina; Parker, Edith A. (April 1, 2013). "Staying cool in a changing climate: Reaching vulnerable populations during heat events". Global Environmental Change. 23 (2): 475–484. Bibcode:2013GEC....23..475S. doi:10.1016/j.gloenvcha.2012.12.011. ISSN 0959-3780. PMC 5784212. PMID 29375195.
  112. ^ Niktash, Amirreza; Huynh, B. Phuoc (July 2–4, 2014). Simulation and Analysis of Ventilation Flow Through a Room Caused by a Two-sided Windcatcher Using a LES Method (PDF). World Congress on Engineering. Lecture Notes in Engineering and Computer Science. Vol. 2. London. eISSN 2078-0966. ISBN 978-9881925350. ISSN 2078-0958. Archived (PDF) from the original on April 26, 2018. Retrieved May 13, 2021.
  113. ^ Zhang, Chen; Kazanci, Ongun Berk; Levinson, Ronnen; Heiselberg, Per; Olesen, Bjarne W.; Chiesa, Giacomo; Sodagar, Behzad; Ai, Zhengtao; Selkowitz, Stephen; Zinzi, Michele; Mahdavi, Ardeshir (November 15, 2021). "Resilient cooling strategies – A critical review and qualitative assessment". Energy and Buildings. 251: 111312. Bibcode:2021EneBu.25111312Z. doi:10.1016/j.enbuild.2021.111312. hdl:2117/363031. ISSN 0378-7788.
  114. ^ Linden, P. F. (1999). "The Fluid Mechanics of Natural Ventilation". Annual Review of Fluid Mechanics. 31: 201–238. Bibcode:1999AnRFM..31..201L. doi:10.1146/annurev.fluid.31.1.201.
  115. ^ Santamouris, M.; Asimakoupolos, D. (1996). Passive cooling of buildings (1st ed.). London: James & James (Science Publishers) Ltd. ISBN 978-1-873936-47-4.
  116. ^ Leo Samuel, D.G.; Shiva Nagendra, S.M.; Maiya, M.P. (August 2013). "Passive alternatives to mechanical air conditioning of building: A review". Building and Environment. 66: 54–64. Bibcode:2013BuEnv..66...54S. doi:10.1016/j.buildenv.2013.04.016.
  117. ^ M.j, Limb (January 1, 1998). "BIB 08: An Annotated Bibliography: Passive Cooling Technology for Office Buildings in Hot Dry and Temperate Climates".
  118. ^ Niles, Philip; Kenneth, Haggard (1980). Passive Solar Handbook. California Energy Resources Conservation. ASIN B001UYRTMM.
  119. ^ "Cooling: The hidden threat for climate change and sustainable goals". phys.org. Retrieved September 18, 2021.
  120. ^ Ford, Brian (September 2001). "Passive downdraught evaporative cooling: principles and practice". Arq: Architectural Research Quarterly. 5 (3): 271–280. doi:10.1017/S1359135501001312. ISSN 1474-0516. S2CID 110209529.
  121. ^ a b Chen, Meijie; Pang, Dan; Chen, Xingyu; Yan, Hongjie; Yang, Yuan (2022). "Passive daytime radiative cooling: Fundamentals, material designs, and applications". EcoMat. 4. doi:10.1002/eom2.12153. S2CID 240331557. Passive daytime radiative cooling (PDRC) dissipates terrestrial heat to the extremely cold outer space without using any energy input or producing pollution. It has the potential to simultaneously alleviate the two major problems of energy crisis and global warming.
  122. ^ Raman, Aaswath P.; Anoma, Marc Abou; Zhu, Linxiao; Rephaeli, Eden; Fan, Shanhui (November 2014). "Passive radiative cooling below ambient air temperature under direct sunlight". Nature. 515 (7528): 540–544. Bibcode:2014Natur.515..540R. doi:10.1038/nature13883. PMID 25428501.
  123. ^ a b Bijarniya, Jay Prakash; Sarkar, Jahar; Maiti, Pralay (November 2020). "Review on passive daytime radiative cooling: Fundamentals, recent researches, challenges and opportunities". Renewable and Sustainable Energy Reviews. 133: 110263. Bibcode:2020RSERv.13310263B. doi:10.1016/j.rser.2020.110263. S2CID 224874019.
  124. ^ Mokhtari, Reza; Ulpiani, Giulia; Ghasempour, Roghayeh (July 2022). "The Cooling Station: Combining hydronic radiant cooling and daytime radiative cooling for urban shelters". Applied Thermal Engineering. 211: 118493. Bibcode:2022AppTE.21118493M. doi:10.1016/j.applthermaleng.2022.118493.
  125. ^ Yang, Yuan; Zhang, Yifan (July 2020). "Passive daytime radiative cooling: Principle, application, and economic analysis". MRS Energy & Sustainability. 7 (1). doi:10.1557/mre.2020.18.
  126. ^ Miranda, Nicole D.; Renaldi, Renaldi; Khosla, Radhika; McCulloch, Malcolm D. (October 2021). "Bibliometric analysis and landscape of actors in passive cooling research". Renewable and Sustainable Energy Reviews. 149: 111406. Bibcode:2021RSERv.14911406M. doi:10.1016/j.rser.2021.111406.
  127. ^ a b Needham, Joseph; Wang, Ling (1991). Science and Civilisation in China, Volume 4: Physics and Physical Technology, Part 2, Mechanical Engineering. Cambridge University Press. ISBN 978-0521058032. OCLC 468144152.
  128. ^ Dalley, Stephanie (2002). Mari and Karana: Two Old Babylonian Cities (2nd ed.). Piscataway, New Jersey: Gorgias Press. p. 91. ISBN 978-1931956024. OCLC 961899663. Archived from the original on January 29, 2021. Retrieved May 13, 2021.
  129. ^ Nagengast, Bernard (February 1999). "Comfort from a Block of Ice: A History of Comfort Cooling Using Ice" (PDF). ASHRAE Journal. 41 (2): 49. ISSN 0001-2491. Archived (PDF) from the original on May 13, 2021. Retrieved May 13, 2021.
  130. ^ Bahadori, Mehdi N. (February 1978). "Passive Cooling Systems in Iranian Architecture". Scientific American. 238 (2): 144–154. Bibcode:1978SciAm.238b.144B. doi:10.1038/SCIENTIFICAMERICAN0278-144.
  131. ^ Smith, Shane (2000). Greenhouse Gardener's Companion: Growing Food and Flowers in Your Greenhouse Or Sunspace. Illustrated by Marjorie C. Leggitt (illustrated, revised ed.). Golden, Colorado: Fulcrum Publishing. p. 62. ISBN 978-1555914509. OCLC 905564174. Archived from the original on May 13, 2021. Retrieved August 25, 2020.
[edit]

 

Photo
Photo
Photo
View GBP
Capacitors are crucial for starting and running the motors in an HVAC system. A faulty capacitor can cause the motor to fail, leading to inefficient operation or complete system shutdown, so replacing it ensures reliable performance.
Signs of a failing capacitor include frequent cycling, humming noises from the unit, delayed start-up, or the air conditioner not blowing cold air. If you notice these symptoms, its likely time for a replacement.
Ignoring a faulty capacitor can lead to increased energy consumption, further damage to other components like the compressor or fan motor, and eventually complete system failure which may result in more costly repairs.
While technically possible for someone with electrical knowledge to replace an HVAC capacitor themselves, it involves handling high-voltage components. Its safer and recommended to hire a professional technician to ensure proper installation and safety compliance.
Capacitors generally last about 10-20 years but should be checked during regular maintenance visits at least once a year. Regular checks help catch potential issues early before they lead to larger problems.