Indoor air quality ( IAQ ) is a term that refers to the air quality in and around buildings and structures, especially with regard to occupant health and comfort. IAQ can be affected by gases (including carbon monoxide, radon, volatile organic compounds), particulates, microbial contaminants (fungi, bacteria), or mass or energy stress that can cause poor health conditions. Source control, filtration and use of ventilation to dilute contaminants are the main methods for improving indoor air quality in most buildings. Residential units can further improve indoor air quality by carpet cleaning and carpet rugs on a regular basis.
The IAQ determination involves collecting air samples, monitoring human exposure to pollutants, collecting samples on building surfaces, and modeling computer airflows within the building.
The IAQ is part of the indoor environmental quality (IEQ), which includes IAQ as well as other physical and psychological aspects of indoor life (eg lighting, visual quality, acoustics, and thermal comfort).
Indoor air pollution in developing countries is a major health hazard. The main source of indoor air pollution in developing countries is the burning of biomass (eg wood, charcoal, dirt, or crop residue) for heating and cooking. The resulting exposure to high particle levels produced between 1.5 million and 2 million deaths in 2000.
Video Indoor air quality
Public pollutants
Passive smokers
Secondhand smoke is tobacco smoke that affects people other than 'active' smokers. Secondhand smoke includes gas and particle phases, with particular hazards arising from carbon monoxide levels (as shown below) and very small particulates (particularly on the size of PM2.5 and PM10) that enter the bronchioles and alveoli in lungs. The only particular method of improving indoor air quality in relation to second-hand smoke is the application of a comprehensive smoke-free law.
Radon
Radon is an invisible radioactive atomic gas produced from radioactive decay of radium, which can be found in rock formations beneath a building or in a particular building material itself. Radon may be the most widespread serious danger for indoor air in the United States and Europe, probably responsible for tens of thousands of deaths from lung cancer each year. There is a relatively simple test tool for do-it-yourself radon gas testing, but if the house is sold, testing should be performed by a licensed person in some US states. The radon gas enters the building as a soil gas and is a heavy gas and thus will tend to accumulate at the lowest level. Radon can also be put into the building through drinking water especially from bathroom showers. Building materials can be a rare source of radon, but little testing is done for stone, stone or tile products brought to the building site; The largest accumulation of radon for well-insulated homes. The half-life for radon is 3.8 days, indicating that once the source is removed, the dangers will be greatly reduced in a few weeks. Radon mitigation methods include sealing concrete floor plates, basement foundations, water drainage systems, or by increasing ventilation. They are usually cost effective and can greatly reduce or even eliminate contamination and related health risks.
Mushrooms and other allergens
These biological chemicals can arise from a number of means, but there are two general classes: (a) growth caused by moisture of the fungal colony and (b) natural substances released into the air such as animal fur and plant pollen. The fungus is always associated with moisture, and its growth can be inhibited by keeping the humidity level below 50%. Humidity buildup in buildings may arise from water that penetrates compromised areas of the building or leather coverings, from pipeline leaks, from condensation due to improper ventilation, or from moisture of soil penetrating parts of buildings. Even something as simple as drying clothes indoors on a radiator can increase the risk of exposure (among other things) Aspergillus - a very dangerous fungus that can be fatal for people with asthma and parents. In areas where cellulosic material (paper and wood, including drywall) becomes damp and fails to dry within 48 hours, mold fungus can propagate and release allergen spores into the air.
In many cases, if the material has failed to dry several days after the suspected water event, the growth of the fungus is suspected in the wall cavity even if not immediately visible. Through a print investigation, which may include a destructive inspection, one must be able to determine the presence or absence of a mold. In situations where there is visible mold and indoor air quality may have been compromised, a mold repair may be required. Printing and inspection testing shall be carried out by independent investigators to avoid conflicts of interest and ensure accurate results; Free printing tests offered by the remediation company are not recommended.
There are several types of fungi that contain toxic compounds (mycotoxins). However, exposure to dangerous levels of mycotoxins through inhalation is not possible in many cases, since the toxins are produced by the fungal body and not at a significant level in the spores that are released. The main hazard of fungal growth, which is related to indoor air quality, comes from the allergic nature of the spore cell wall. More serious than most allergenic properties is the mushroom ability to trigger episodes in people who already have asthma, serious respiratory diseases.
Carbon monoxide
One of the most toxic indoor air contaminants is carbon monoxide (CO), a colorless, odorless gas that is a by-product of incomplete burning of fossil fuels. Common sources of carbon monoxide are tobacco smoke, space heaters using fossil fuels, damaged central heating furnaces and car disposal. By reducing the brain of oxygen, high levels of carbon monoxide can cause nausea, unconsciousness, and death. According to the Conference of American Government Industrial Hygiene Experts (ACGIH), the average time limit (TWA) for carbon monoxide (630-08-0) is 25 ppm.
The level of indoor CO is increased systematically due to the increasing implementation of smoke-free laws.
Volatile organic compounds
The volatile organic compound (VOC) is emitted as a gas of a particular solid or liquid. VOCs include a variety of chemicals, some of which may have adverse short-term and long-term health effects. The concentrations of many VOCs are consistently higher in the room (up to ten times higher) than outdoors. VOCs are emitted by a myriad of thousands of products. Examples include: paints and lacquers, paint dancers, cleaning supplies, pesticides, building materials and furniture, office equipment such as photocopiers and printers, correction fluids and carbonless copier paper, graphic materials and crafts including glue and adhesives, permanent markers, and photography solutions.
Chlorinated drinking water releases chloroform when hot water is used at home. Benzene is emitted from fuel stored in a connected garage. Overheated cooking oil removes acrolein and formaldehyde. A meta-analysis of 77 VOC surveys in homes in the US found the top ten most in-risk VOCs in the air were acrolein, formaldehyde, benzene, hexachlorobutadiene, acetaldehyde, 1,3-butadiene, benzyl chloride, 1,4-dichlorobenzene, carbon tetrachloride, acrylonitrile, and vinyl chloride. These compounds exceed health standards in most homes.
Organic chemicals are widely used as ingredients in household products. Paints, varnishes and candles all contain organic solvents, such as many cleaning products, disinfectants, cosmetics, cleansers, and hobbies. Fuel consists of organic chemicals. All of these products can release organic compounds during use, and, to some extent, when they are stored. Emission testing of building materials used indoors has become increasingly common for floor coverings, paints, and many other important indoor building materials and finishes.
Some initiatives envisage to reduce indoor air contamination by limiting VOC emissions from the product. There are regulations in France and in Germany, and many voluntary ecolabel and rating systems contain low VOC emission criteria such as EMICODE, M1, Blue Angel and Indoor Air Comfort in Europe, as well as the California Standard CDPH Section 01350 and several others in the US. These initiatives are changing markets where more and more low-emission products have been available over the last few decades.
At least 18 Microbial VOCs (MVOCs) have been characterized including 1-octen-3-ol, 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 first of these compounds is called an alcoholic fungus. The last four are products of the Stachybotrys chartarum , which has been linked to sick building syndrome.
Legionella
Legionellosis or Legionnaire Disease is caused by water-borne bacteria Legionella that grows best in slow-moving or still-warm water. The main exposure route is through the creation of aerosol effects, most often from evaporative cooling towers or showers. Common sources of Legionella in commercial buildings are from poorly placed or maintained evaporative cooling towers, which often release water in the aerosols that can enter the nearest ventilation intake. Outbreaks in medical facilities and nursing homes, where patients are immuno-suppressed and immuno-weak, are the most frequently reported cases of Legionellosis. More than one case has involved an outdoor fountain in public places. The presence of Legionella in commercial building water supplies is poorly reported, since healthy people need heavy exposure to get infections.
Legionella testing usually involves collecting water samples and surface swabs from evaporative cooling basins, shower heads, faucets/taps, and other locations where warm water is collected. Samples were then cultured and the colony-forming units (cfu) of Legionella were quantified as cfu/Liter.
Legionella is a protozoan parasite such as amoeba, and thus requires conditions suitable for both organisms. Bacteria form biofilms that are resistant to chemical and antimicrobial treatments, including chlorine. Remediation for Legionella outbreaks in commercial buildings varies, but often includes very hot water streams (160 ° F, 70 ° C), water sterilization standing in evaporative cooling basins, shower head replacements, and in some cases flushes of heavy metals salt. Preventive measures include adjusting normal hot water levels to allow 120 ° F (50 ° C) in the faucet, evaluating the facility layout design, removing the faucet aerator, and periodic testing in the area of ​​the suspect.
Other bacteria
There are many bacterial health significances found in the indoor air and on the indoor surface. The role of microbes in indoor environments is increasingly studied using modern gene-based analysis of environmental samples. Currently efforts are being made to connect microbial ecologists and indoor air scientists to forge new methods for analysis and to better interpret results.
"There are about ten times as many bacterial cells in human flora as there are human cells in the body, with large amounts of bacteria on the skin and as intestinal flora." Most of the bacteria found in the air and dust in the house are detached from humans. Among the most important bacteria known to occur in indoor air are Mycobacterium tuberculosis, Staphylococcus aureus, Streptococcus pneumoniae.
Asbestos fibers
Many of the common building materials used before 1975 contain asbestos, such as some floor tiles, ceiling tiles, shingles, fireproofing, heating systems, pipe wrapping, mud recording, mastics, and other insulating materials. Typically, significant release of asbestos fibers does not occur unless building materials are disrupted, such as by cutting, sanding, drilling, or building renovations. Removal of asbestos-containing materials is not always optimal because the fibers can spread into the air during the removal process. Management programs for ingredients containing asbestos intact are often recommended instead.
When materials containing asbestos are damaged or destroyed, microscopic fibers are dispersed into the air. Inhaling asbestos fibers during long exposure times was associated with an increased incidence of lung cancer, specifically the specific form of mesothelioma. The risk of lung cancer from inhaling asbestos fibers is significantly greater for smokers, but there is no definite association with damage caused by asbestosis. The symptoms of the disease usually do not appear until about 20 to 30 years after the first exposure to asbestos.
Asbestos is found in old homes and buildings, but most often occurs in schools, hospitals and industrial settings. Although all asbestos is dangerous, the product is fragile, for example. coatings and sprayed insulations, pose significantly higher hazards as they are more likely to release fibers into the air. The US Federal Government and several states have set standards for acceptable indoor asbestos fiber level. There are strict rules that apply to schools.
Carbon dioxide
Carbon dioxide (CO 2 ) is relatively easy to measure a replacement for the inner pollutants emitted by humans, and correlates with human metabolic activity. Carbon dioxide at very high levels indoors can cause drowsy dwellers, headaches, or functioning at lower activity levels. Extra CO 2 level is usually 350-450 ppm whereas maximum indoor CO level 2 is considered to be acceptable is 1000 ppm. Humans are the source of carbon dioxide in the main room in most buildings. The indoor CO level 2 is an indicator of the adequacy of outdoor air vent relative to the density of indoor occupants and metabolic activity.
To eliminate most complaints, the total indoor CO level 2 should be reduced to a margin of less than 600 ppm above the outer surface. The National Institute for Occupational Safety and Health (NIOSH) considers that indoor carbon dioxide concentrations exceeding 1,000 ppm are markers that indicate inadequate ventilation. The British standard for schools says that carbon dioxide in all study and teaching rooms, when measured at the height of the sitting head and the average throughout the day should not exceed 1,500 ppm. The whole day refers to normal school hours (ie 9:00 am to 3:30 pm) and includes periods not as busy as lunch breaks. In Hong Kong, the EPD sets indoor air quality objectives for office buildings and public places where carbon dioxide levels below 1,000 ppm are considered good. European standards limit carbon dioxide to 3,500 ppm. OSHA limits the concentration of carbon dioxide in the workplace to 5,000 ppm for a long time, and 35,000 ppm for 15 minutes. These higher limits are related to avoiding loss of consciousness (fainting), and not addressing the cognitive and energy performance disorders, which begin to occur at lower carbon dioxide concentrations.
The concentration of carbon dioxide increases as a result of human occupancy, but lags behind in cumulative occupancy and fresh air intake. The lower the air exchange rate, the slower the accumulation of carbon dioxide to the apparent "steady state" concentration on which the NIOSH and English references are based. Therefore, the measurement of carbon dioxide for the purpose of assessing the adequacy of ventilation needs to be done after a period of permanent occupancy and ventilation - at school at least 2 hours, and at the office at least 3 hours - for concentration to be a reasonable indicator. adequacy of ventilation. Portable instruments used to measure carbon dioxide should often be calibrated, and outdoor measurements used for calculations should be made in the near future to indoor measurements. Correction for temperature effects on outdoor measurements may also be required.
The concentration of carbon dioxide in a confined or limited space can increase to 1,000 ppm within 45 minutes of the enclosure. For example, in an office measuring 3.5 x 4 meters (11 feet), atmospheric carbon dioxide increases from 500 ppm to more than 1,000 ppm in 45 minutes of ventilation shutdown and window and door closures.
Ozone
Ozone is generated by ultraviolet light from the Sun that strikes the Earth's atmosphere (especially in the ozone layer), lightning, certain high-voltage electrical devices (such as air ionizers), and as a by-product of other types of pollution.
Ozone exists in greater concentration at altitudes normally flown by passenger jets. The reaction between ozone and onboard substances, including oil and skin cosmetics, can produce toxic chemicals as a by-product. Ozone itself also irritates lung tissue and is harmful to human health. Larger jets have ozone filters to reduce cabin concentration to safer and more comfortable levels.
The outside air used for ventilation may have enough ozone to react with common indoor pollutants as well as skin oils and chemicals or other indoor air surfaces. Special attention is justified 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 as well as fine particles and ultrafine. Ventilation with outside air containing high ozone concentrations can complicate remediation efforts.
Ozone is on the list of six air pollutants. The Clean Air Act of 1990 requires the US Environmental Protection Agency to set a National Air Quality Standard (NAAQS) for six indoor air pollutants that are harmful to human health.. There are also several other organizations that have proposed air standards such as Occupational Safety and Health (OSHA), the National Institute for Occupational Health and Safety (NIOSH), and the World Health Organization (WHO). The OSHA standard for Ozone concentrations in space is 0.1 ppm. While the NAAQS and EPA standards for ozone concentrations are limited to 0.07 ppm.. The regulated ozone type is the ozone at the soil surface which is within the breathing range of most building occupants
Particulate
Atmospheric particles, also known as particulates can be found indoors and can affect occupant health. The authorities have set the standard for maximum particulate concentration to ensure indoor air quality.
Maps Indoor air quality
Cognitive prompt prompt
In 2015, experimental studies reported the detection of significant (epicodic) cognitive impairment of airborne impurities inhaled by test subjects who were not informed of changes in air quality. Researchers at Harvard University and SUNY Upstate Medical University and Syracuse University measured 24 participants' cognitive performance in three different controlled laboratory atmospheres that simulated those found in "conventional" and "green" buildings, as well as green buildings with improved ventilation. Performance is evaluated objectively using the widely used Strategic Management Simulation simulation tool, which is a well-validated assessment test for executive decision making in unlimited situations that allow initiative and improvisation. Significant deficits are observed in performance scores achieved in increasing concentrations of either volatile organic compounds (VOCs) or carbon dioxide, while keeping other factors constant. The highest impurity levels achieved are not uncommon in some classrooms or office environments.
Influence of indoor plants
Ornamental plants together with the media in which they grow can reduce the components of indoor air pollution, especially volatile organic compounds (VOCs) such as benzene, toluene, and xylene. Plants release CO 2 and release oxygen and water, despite the quantitative impacts for small house plants. Most of its effects are attributed to the growing medium itself, but even these effects have limited limits associated with the type and quantity of medium and airflow through the medium. The influence of house plants on VOC concentrations was investigated in one study, conducted in static spaces, by NASA for possible use in space colonies. The results showed that the elimination of a chemical challenge was roughly equivalent to that provided by vents occurring in very energy-efficient places with very low ventilation rates, an air exchange rate of about 1/10 per hour. Therefore, air leakage in most homes, and in non-residential buildings as well, will generally remove chemicals faster than researchers reported for plants tested by NASA. The most effective household crops reported include aloe vera, ivy English, and Boston ferns to remove chemicals and biological compounds.
Plants also appear to reduce microbes in the air, mold, and increase moisture. However, the increase in moisture itself can lead to increased levels of mold and even VOCs.
As the concentration of carbon dioxide increases indoors relative to outdoor concentrations, it is simply an indicator that ventilation is inadequate to remove metabolic products associated with human occupancy. Plants need carbon dioxide to grow and release oxygen when they consume carbon dioxide. A study published in the journal Environmental Science & amp; The technology considers the rate of absorption of ketones and aldehydes by the peace lily (Spathiphyllum clevelandii) and gold pothos (Epipremnum aureum.) Akira Tani and C. Nicholas Hewitt found "long-term fumigation results reveal that the total absorption amount is 30 -100 times more than the amount dissolved in leaves, indicating that volatile organic carbon is metabolized in leaves and/or transplanted through petiole. "It is worth noting that the researchers sealed the plants in Teflon bags. "No loss of VOC is detected from the pocket when the plant is not present, but when the plant is in the bag, the level of aldehyde and ketone both decreases slowly but continuously, indicating the removal by the plant". Studies conducted in enclosed pockets do not precisely reproduce conditions in attractive indoor environments. Dynamic conditions with outside air vents and processes associated with the surface of the building itself and its contents and occupants need to be studied.
While the results show house plants may be effective for removing some VOCs from the air supply, a review of studies between 1989 and 2006 on ornamental plant performance as an air purifier, presented at the Healthy House 2009 conference in Syracuse, NY, concluded ".. The deep crop has few benefit, if any, to move indoor air from VOCs in residential and commercial buildings. "
Because high humidity is associated with increased mold growth, allergic responses, and respiratory responses, the presence of additional moisture from crops may be undesirable in all indoor settings.
HVAC Design
The concept of eco-friendly design also includes aspects related to the commercial and residential heating and ventilation, ventilation and air conditioning (HVAC) industries. Among several considerations, one of the topics attended was the problem of indoor air quality throughout the design and construction stages of a building's life.
One technique for reducing energy consumption while maintaining adequate air quality, is demand-driven ventilation. Instead of setting the throughput at a fixed air replacement level, the carbon dioxide sensor is used to dynamically control the rate, based on emissions from the actual building occupants.
Over the last few years, there has been much debate among indoor air quality experts about the precise definition of indoor air quality and specifically what constitutes acceptable "indoor air quality".
One way to ensure indoor air health is by the effective frequency of interior air rotation with replacement with the outside air. In the UK, for example, classrooms are required to have 2.5 hourly air changes per hour. In spaces, exercise rooms, dining rooms, and physiotherapy, ventilation should be sufficient to limit carbon dioxide to 1,500 ppm. In the US, and according to ASHRAE Standards, ventilation in the classroom is based on the amount of outdoor air per passenger plus the amount of outdoor air per unit floor area, not the hourly air change. Because indoor carbon dioxide comes from residents and outside air, the adequacy of ventilation per occupant is indicated by indoor concentrations minus the outdoor concentration. The value of 615 ppm above the outdoor concentration indicates about 15 cubic feet per minute of outdoor air per adult who performs immovable office work in which the outdoor air contains 385 ppm, the current global average CO concentration 2 . In the classroom, the requirements in the ASHRAE 62.1 standard, Ventilation for Acceptable Indoor Air Quality, will typically generate about 3 air changes per hour, depending on the density of the occupants. Of course, residents are not the only source of pollutants, so outside air ventilation may need to be higher when unusual or strong sources of pollution are in the room. When outdoor air is polluted, bringing in more outside air may actually worsen the overall quality of indoor air and worsen some occupant symptoms associated with outside air pollution. Generally, air abroad is better than indoor city air. The leakage of exhaust gas may occur from the furnace metal exhaust pipe leading to the chimney when there is leakage in the pipe and the diameter of the gas pipeline area has been reduced.
The use of air filters can trap some air pollutants. The Energy Efficiency and Renewable Energy Department Department of Energy wrote "[Water] Filtration must have a Minimum Efficiency Reporting Value (MERV) of 13 as determined by ASHRAE 52.2-1999." The air filter is used to reduce the amount of dust that reaches the wet roll. Dust can serve as food to grow mushrooms on wet rolls and channels and can reduce coil efficiency.
Humidity management and humidity control require HVAC operating systems as designed. Moisture management and humidity control may conflict with efforts to try to optimize operations to save energy. For example, humidity and humidity control management requires systems to be arranged to supply Make Up Water at lower temperatures (design level), rather than higher temperatures sometimes used to conserve energy in predominantly cooler climatic conditions. However, for most of the US and many parts of Europe and Japan, for most hours of the year, outdoor temperatures are cool enough so that air does not need further cooling to provide thermal comfort indoors. However, high humidity outside the room creates a need for careful attention to the level of humidity in the room. High humidity induces mold growth and indoor humidity is associated with a higher prevalence of resident respiratory problems.
"Dew point temperature" is the absolute measure of moisture in the air. Some facilities are being designed with dew design points below 50 Â ° F, and some above and below 40 Â ° F. Some facilities are being designed using desiccant wheels with gas-fired heaters to dry enough wheels to get the dew point needed. In such a system, once the moisture is removed from the air of makeup, the cooling coil is used to lower the temperature to the desired level.
Commercial buildings, and sometimes housing, are often kept under relatively positive relative to outside air pressure to reduce infiltration. Limiting infiltration helps with moisture management and moisture control.
Dilution of indoor pollutants with outside air is effective as far as outside air is free from harmful pollutants. Ozone in the outdoor air takes place indoors at reduced concentrations because ozone is highly reactive with many chemicals found indoors. The products of the reaction between ozone and many common indoor pollutants include organic compounds that may be smelly, irritating, or toxic than those from which they form. These ozone chemical products include formaldehyde, higher molecular weight aldehydes, acidic aerosols, and fine particles and ultrafine, among others. The higher the level of outdoor ventilation, the higher the ozone concentration in the room and the more likely the reaction will occur, but even at low levels, the reaction will occur. This suggests that ozone should be removed from air vents, especially in areas where ozone levels outside are often high. Recent research has shown that mortality and morbidity are increasing in the general population during higher ozone periods and the threshold for this effect is about 20 parts per billion (ppb).
Build ecology
It is common to assume that buildings are physical entities that are not lifeless, relatively stable over time. This implies that there is little interaction between the triad of buildings, what is in them (the inhabitants and the content), and what is around them (the wider environment). We usually see the majority of the material mass in a building as a relatively unchanging physical material over time. In fact, the original nature of buildings can be seen as the result of a series of complex dynamic interactions between their physical, chemical, and biological dimensions. Buildings can be described and understood as complex systems. Research that applies the approach used by ecologists to understand ecosystems can help improve our understanding. "Building ecology" is proposed here as applying that approach to the built environment given the dynamic system of the building, its inhabitants, and the larger environment.
Buildings continue to evolve as a result of changes in the environment around them as well as the occupants, materials, and activities in them. The various surfaces and air within the building continue to interact, and these interactions produce changes in each. For example, we may see a window change slightly from time to time as it becomes dirty, then cleaned up, piling up the dirt again, cleaning it again, and so on for the rest of its life. In fact, the "impurities" we see may develop as a result of the interactions between moisture, chemicals, and biological materials found there.
Buildings are designed or intended to respond actively to some of these changes and surroundings by heating, cooling, ventilation, air cleaning or illumination systems. We clean, clean, and retain surfaces to improve appearance, performance, or longevity. In other cases, such changes subtly or even dramatically alter buildings in ways that may be important to their own integrity or their impact on building occupants through the evolution of the physical, chemical, and biological processes that determine them at any time. We may find it useful to combine the tools of physics with biological sciences and, in particular, some of the approaches used by scientists who study ecosystems, to gain a better understanding of the environment in which we spend most of our time, our buildings.
The building ecology was first described by Hal Levin in an article in the April 1981 issue of Progressive Architecture.
Institutional program
IAQ topics have become popular because of the greater awareness of health problems caused by fungi and triggers for asthma and allergies. In the US, awareness has also been enhanced by the involvement of the US Environmental Protection Agency, which has developed the "IAQ Tools for Schools" program to help improve indoor environmental conditions in educational institutions (see external links below). The National Institute for Occupational Safety and Health undertakes Health Hazard Evaluation (HHEs) in the workplace at the request of employees, authorized representatives of employees, or employers, to determine whether substances normally found in the workplace have potentially toxic effects, including indoor air quality.
Various scientists work in the field of indoor air quality including chemists, physicists, mechanical engineers, biologists, bacteriologists, 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.
Source of the article : Wikipedia
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