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What Causes Indoor Air Problems?

Indoor pollution sources that release gases or particles into the air are the primary cause of indoor air quality problems in homes. Inadequate ventilation can increase indoor pollutant levels by not bringing in enough outdoor air to dilute emissions from indoor sources and by not carrying indoor air pollutants out of the home. High temperature and humidity levels can also increase concentrations of some pollutants.

There are many sources of indoor air pollution in any home. These include combustion sources such as oil, gas, kerosene, coal, wood, and tobacco products; building materials and furnishings as diverse as deteriorated, asbestos-containing insulation, wet or damp carpet, and cabinetry or furniture made of certain pressed wood products; products for household cleaning and maintenance, personal care, or hobbies; central heating and cooling systems and humidification devices; and outdoor sources such as radon, pesticides, and outdoor air pollution.

The relative importance of any single source depends on how much of a given pollutant it emits and how hazardous those emissions are. In some cases, factors such as how old the source is and whether it is properly maintained are significant. For example, an improperly adjusted gas stove can emit significantly more carbon monoxide than one that is properly adjusted.

Some sources, such as building materials, furnishings, and household products like air fresheners, release pollutants more or less continuously. Other sources, related to activities carried out in the home, release pollutants intermittently. These include smoking, the use of unvented or malfunctioning stoves, furnaces, or space heaters, the use of solvents in cleaning and hobby activities, the use of paint strippers in redecorating activities, and the use of cleaning products and pesticides in housekeeping. High pollutant concentrations can remain in the air for long periods after some of these activities.

If too little outdoor air enters a home, pollutants can accumulate to levels that can pose health and comfort problems. Unless they are built with special mechanical means of ventilation, homes that are designed and constructed to minimize the amount of outdoor air that can "leak" into and out of the home may have higher pollutant levels than other homes.

However, because some weather conditions can drastically reduce the amount of outdoor air that enters a home, pollutants can build up even in homes that are normally considered "leaky." Radon can enter and collect inside homes and other buildings that are not built with radon-resistant techniques. However, buildings constructed with radon-resistant techniques can ensure lower radon levels, energy efficiency, and a safer home. Read more about what steps to take both to reduce the risk from existing sources of indoor air pollution and how to prevent new problems from occurring in The Inside Story- A Guide to Indoor Air Quality.

Healthy Indoor Air for America's Homes Project

EPA and the U.S. Department of Agriculture-Cooperative State Research, Education and Extension Service have developed a national consumer education program concerned with improving the quality of indoor air in homes. The project helps provide awareness of indoor air quality issues such as Carbon Monoxide and other combustion products, Radon, Formaldehyde, Molds, Lead, and Air Hazards associated with remodeling and household products.

Read the brochure: Indoor Air Hazards Every Homeowner Should Know About.

The brochure is also available in Spanish as," Contaminantes Peligrosos del Aire Que Cada Dueño De Hogar Debe Conocer.

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Last Revised: July15, 1999