Indoor air quality

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. Recent findings have demonstrated that indoor air is often more polluted than outdoor air (albeit with different pollutants) although this has not changed the common understanding of air pollution. In fact, indoor air is often a greater health hazard than the corresponding outdoor setting. Using ventilation to dilute contaminants, filtration, and source control are the primary methods for improving indoor air quality in most buildings.

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.

1 Risk Assessment
2 HVAC engineering issues
3 Institutional Roles
4 How To Improve Indoor Air Quality
5 References
6 See also
7 External links

[edit] Risk Assessment

[edit] Radon

Radon is the invisible, radioactive atomic gas that results from radioactive decay of some forms of uranium 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 can actually be a significant 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 indicating that once the source is removed, the hazard will be greatly reduced within a few weeks.

[edit] 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 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 a lack of air circulation, mold colonies can propagate and release mycotoxins] into the air. In a situation where there is visible mold and the indoor air quality may have been compromised a mold inspection and/ or mold remediation may be needed. Through an inspection one should be able to determine the presence or absence of mold, which can cause allergic reactions and respiratory effects; there are some varieties of mold that are toxic in nature. Indoors, mold growth can be inhibited by keeping humidity levels between forty and sixty percent and by eliminating leaks or moisture condensation and accumulation

[edit] Carbon Monoxide

One of the most acutely toxic indoor air contaminants is carbon monoxide (CO), a colorless, odorless gas that is a byproduct of incomplete combustion of fossil fuels. Common sources of carbon monoxide are tobacco smoke, space heaters using fossil fuels, defective 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.

[edit] Legionella

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.

[edit] 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.

[edit] Carbon Dioxide

Carbon dioxide is a surrogate for indoor pollutants emitted by humans and correlates with human metabolic activity. Carbon dioxide at levels that are unusually high indoors may cause occupants to grow drowsy, get headaches, or function at lower activity levels. Humans are the main indoor source of carbon dioxide. Indoor levels are an indicator of the adequacy of outdoor air ventilation relative to indoor occupant density and metabolic activity. To eliminate most Indoor Air Quality complaints, total indoor carbon dioxide should be reduced to below 600 ppm above outdoor levels. NIOSH considers that indoor air concentrations of carbon dioxide that exceed 1,000 ppm are a marker suggesting inadequate ventilation (1,000 ppm equals 0.1%). ASHRAE recommends that carbon dioxide levels not exceed 700 ppm above outdoor ambient levels. The UK standards for schools say that carbon dioxide in all teaching and learning spaces, when measured at seated head height and averaged over the whole day should not exceed 1,500 ppm. The whole day refers to normal school hours (i.e. 9.00am to 3.30pm) and includes unoccupied periods such as lunch breaks. Canadian standards limit carbon dioxide to 3500 ppm. OSHA limits carbon dioxide concentration in the workplace to 5,000 ppm for prolonged periods, and 35,000 ppm for 15 minutes.

[edit] HVAC engineering issues

A basic way of measuring 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.

The use of air filters can trap some of the air pollutants. The Department of Energy's Energy Efficiency and Renewable Energy section wrote "[Air] Filtration should have a Minimum Efficiency Reporting Value (MERV) of 13 as determined by ASHRAE 52.2-1999."^[1] Air filters are used to reduce the amount of dust that reaches the wet coils. Dust can serve as food to grow molds on the wet coils and ducts and can reduce the efficiency of the coils.

Moisture management and humidity control requires operating HVAC systems as designed. Moisture management and humidity control may conflict with efforts to try to optimize the operation 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. However, high humidity outdoors creates the need for careful attention to humidity levels indoors. High humidities give rise to mold growth and moisture indoors is associated with a higher prevalence of occupant respiratory problems.

The "dew point temperature" is an absolute measure of the moisture in air. Some facilities are being designed with the design dew points in the lower 50's °F, and some in the upper and lower 40's °F. Some facilities are being designed using desiccant wheels with gas fired heater to dry out the wheel enough to get the required dew points. 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.

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. Recent research has shown that mortality and morbidity increase in the general population during periods of higher outdoor ozone and that the threshold for this effect is around 20 parts per billion (ppb).

[edit] 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 and the American Indoor Air Quality Council. AIHA and A2LA both offer laboratory accreditation programs that relate to indoor air quality.

[edit] How To Improve Indoor Air Quality

According to the National Safety Council, Americans spend about 90 percent of their time indoors, and 65 percent of that time at home. Thus poor indoor air quality can have a significant impact on people’s lives, especially those who are most vulnerable: infants and children, pregnant women, the elderly, and those who have chronic illnesses.

Steps can be taken to help improve indoor air quality at home, the workplace, and in other indoor environments. Some of those steps include the following:

Understand the role of Green Cleaning

Introduce toxin-consuming plants to your home, office, and other indoor environments. Certain plants, including philodendron, spider plants, golden pothos, peace lilies, bamboo palms, mums, and English ivy remove dangerous toxins (e.g., formaldehyde, carbon monoxide, benzene, and others) from the air, according to research. However, the amount of these pollutants removed by plants is actually minuscule compared with the removal that occurs even at very low rates of outdoor air ventilation. There is also a risk of increasing indoor humidity levels and of promoting mold growth when indoor plants are not properly maintained. See: List of air filtering plants

Use natural household cleaning products and reduce exposure to potentially toxic airborne substances.

Use natural pest control techniques indoors whenever possible. Banish pesticides from your garden and lawn as well, as these toxins can easily be transported into the house on shoes and clothing and by air.

Keep your plumbing traps filled with water to help prevent sewer gas from entering the building.

Regularly clean the vents in your kitchen, bathroom, and dryer, and make sure they operate properly.

Do not smoke or allow smoking in your home, and avoid indoor areas where smoking takes place.

Avoid or reduce biological contaminants by maintaining humidifiers, dehumidifiers, and air conditioners; emptying water trays in dehumidifiers, air conditioners, and refrigerators frequently; drying or removing any water-damaged carpets or furniture; and routinely cleaning bedding and items used by pets.

Prevent carbon monoxide exposure by keeping gas appliances properly serviced, having your central heating system inspected and cleaned yearly, and never idling your car inside an attached garage.

Change filters on central cooling and heating systems and air cleaners according to the manufacturer’s directions.

Test your home for radon. Radon can seep into the house from contaminated earth and rock under the home, or from well water and/or building materials. Easy, do-it-yourself kits can be purchased at hardware and other retail outlets.

[edit] References

Salthammer, T.(ed.)1999. "Organic Indoor Air Pollutants — Occurrence, Measurement, Evaluation". Wiley-VCH, Germany.
Spengler, J.D. and Samet, J.M. (1991). "Indoor air pollution: A health perspective". Johns Hopkins University Press, Baltimore.
Spengler, J.D., Samet, J.M. & McCarthy, J.F (2001). "Indoor Air Quality Handbook". McGraw–Hill, NY. ISBN 0-07-445549-4.

^ [1] DOE EERE Indoor Air Quality - MERV 13 Air Filters

[edit] See also

[edit] External links

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Categories: Health risks | Air pollution | Building biology | Industrial hygiene | Building engineering

Indoor air quality

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