Indoor air quality
From Free net encyclopedia
Indoor Air Quality (IAQ) deals with the content of interior air that could affect health and comfort of building occupants. The IAQ may be compromised by microbial contaminants (mold, bacteria), chemicals(such as carbon monoxide,radon}, allergens, or any mass or energy stressor that can induce health effects. Often it is perceived that outdoor air is polluted, but indoor air is acceptable. Scientific studies illustrate the falsity of this perception, and, in fact, indoor air is often a greater health hazard than the corresponding outdoor setting.
Techniques for analyzing IAQ include collection of air samples, collection of samples on building surfaces and computer modelling of air flow inside buildings. The resulting samples can be analyzed for mold, bacteria, chemicals or other stressors. These investigations can lead to an understanding of the sources of the contaminants and ultimately to strategies for removing the unwanted elements from the air.
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Carbon Monoxide
One of the most acutely toxic indoor air contaminants is carbon monoxide(CO), a colorless, odorless gas that is a byprocuct of imcomplete combustion of fossil fuels. Common sources of carbon monoxide are tobacco smoke,space heaters using fossil fuels, central heating furnaces and automobile exhaust. Improvements in indoor levels of CO are systematically improving from increasing numbers of smoke-free restaurants and other legislated non-smoking buildings. By depriving the brain of oxygen, high levels of carbon monoxide can lead to nausea, unconsiousness and death.
Radon
Radon is an invisible, radioactive atomic gas that results from radioactive decay of some forms of radium that 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, probably responsible for tens of thousands of lung cancer deaths per annum. There are relatively simple tests for radon gas, but these tests are not commonly done, even in areas of known systematic hazards. Radon is a very heavy gas and thus will tend to accumulate at the floor level. Building materials are actually a signicant source of radon, but very little testing is done for stone, rock or tile products brought into building sites. The half life for radon is 3.8 days incicating that once the source is removed, the hazard will be greatly reduced within a few weeks.
Molds and other Allergens
These biological agents can arise from a host of means, but there are two common classes: (a) moisture induced growth of mold spore colonies and (b) natural substances released into the air such as animal dander and plant pollen. Moisture buildup inside buildings may arise from water penetrating compromised areas of the building skin, from plumbing leaks or from ground moisture penetrating a building slab. Especially in the absence of light and with lack of air circulation, mold colonies can propagate on surfaces and eventually enter the air. Many of these mold types can cause allergic reactions and respiratory effects; there are some varieties of mold that are toxic in nature.
Legionellosis
Legionellosis or Legionnaire's Disease is caused by a waterborne bacterium, which is probably the most common serious health threat to building interiors, since mortality is high in infected patients. The number of instances of this disease is higher than commonly understood. The bacterium itself thrives on warm moist substrates and hence is usually associated with a plumbing misdesign or malfunction.
Asbestos Fibers
The U.S.Federal Government and some states have set standards for acceptable levels of asbestos fibers in indoor air. Many common building materials used before 1975 contain asbestos, such as some floor tiles, ceiling tiles, taping muds, pipe wrap, mastics and other insulation materials. Normally significant releases of asbestos fiber do not occur unless the building materials are disturbed, especially by sanding, drilling or building remodelling. There are particularly stringent regulations applicable to schools and residences. Inhalation of asbestos fibers over long exposure times is associated with increased incidence of lung cancer.
Institutional Roles
The topic of IAQ has become popular due to the greater awareness of health problems caused by mold and triggers to asthma and allergies. Awareness has also been increased by the involvement of the Environmental Protection Agency. They have developed an "IAQ Tools for Schools" program to help improve the indoor environmental conditions in educational institutions (see external link below).
A variety of 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, American Indoor Air Quality Council, Indoor Environmental Institute, Indoor Air Quality Association, and the Indoor Environmental Standards Organization. AIHA and A2LA both offer laboratory accreditation programs that relate to indoor air quality.