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Indoor Air Quality

The air in your home may be more polluted than outdoor air in even the largest and most heavily industrialized cities.

Research has revealed that Americans spend about 90 percent of their time indoors. So, for most people, the air pollutants most likely to affect them are the ones that they will encounter in their own homes and places of business. While levels of pollution from individual sources at home may not pose a significant risk by themselves, most homes have more than one source of pollutants. The cumulative effects of these sources can be dangerous. Fortunately, there are steps you can take both to reduce the risk and to prevent new problems from arising.

What pollutes the air in a home?

Indoor pollution sources fall into several general categories. How many of these do you have in your home?

Combustion sources: oil, gas, kerosene, coal, or wood.

Building materials and furnishings: cabinetry or furniture made of certain compressed-wood products: insulation containing asbestos; damp or wet carpeting.

Household products: cleaning and maintenance products, personal care items, and hobby products.

Central heating and cooling systems, and humidification devices. Outside sources that come inside: radon, pesticides, and outdoor air pollution.

What effect does ventilation have?

Inadequate ventilation can increase indoor pollutant levels by not bringing in sufficient outside air to dilute emissions from indoor sources. High temperature and humidity levels can also increase the concentration of some pollutants.

The rate at which outside air replaces indoor air is called the air exchange rate. Your home exchanges air with the outdoors in three ways:

Infiltration - air flowing through construction joints and around windows and doors, as well as from crawl spaces underneath homes.

Natural ventilation - air entering through open doors and windows.

Mechanical ventilation - devices including everything from simple outdoor-vented fans to sophisticated air-handling systems that mix indoor and outdoor air or remove polluted air from the whole house.

When the combination of infiltration, natural ventilation, and mechanical ventilation doesn't produce a vigorous air exchange rate, pollutants inside the home can build up.

How can you recognize bad indoor air?

Some health effects can be symptoms of an air quality problem, especially if they appear after you move to a new residence, remodel or refurnish a home, or treat your home with pesticides. If you think you have symptoms that could be related to your home environment, consult your doctor or your local health department.

Even if you don't have noticeable symptoms, you should try to improve your indoor air quality. The earliest symptoms of some long-term health problems, such as some respiratory illnesses and cancer, don't appear until years after damaging exposure.

Identify potential sources of indoor air pollution. Although the presence of such sources doesn't necessarily mean you have a problem, being aware of the type and number of potential pollutants can help you assess the quality of the air in your home.

Examine your lifestyle and activities. Do you smoke? Do you use solvents in cleaning or in hobby activities? Do you use paint strippers in redecorating activities? What kinds of cleaners and pesticides do you use when housekeeping?

Look for signs of air flow problems in your home. Can you detect any smelly or stuffy air, moisture condensation on windows or walls, signs of water leakage, or areas where books or shoes become moldy? Is your central heating or cooling equipment dirty? Does your home have damaged flues or chimneys?

What about radon?

Radon is a colorless, odorless gas that occurs naturally and is found everywhere at very low levels. Exposure to radon becomes a concern when radon gets trapped indoors so that concentrations build up in indoor air.

Lung cancer is associated with exposure to elevated levels of radon. The Environmental Protection Agency estimates that between 5,000 and 20,000 lung cancer deaths each year may be attributed to radon.

The federal government recommends that you measure the level of radon in your home. Inexpensive devices for measuring radon are widely available. For pollutants other than radon, testing can be expensive. Consult your local health department or an air quality professional before monitoring for these other pollutants.

How can you improve your air at home?

Here are three basic strategies for improving indoor air quality.

Source Control
Eliminate individual sources of pollution or reduce their emissions. Some sources, like insulation containing asbestos, can be sealed or enclosed; others, like gas stoves, can be adjusted to decrease emissions. Source control can be the most cost-efficient approach to improving air quality, because it is more energy-efficient than increasing ventilation.

Ventilation Improvement
Opening windows and doors, when the weather permits, increases the natural ventilation rate and can result in immediate air quality improvement. Turning on bathroom or kitchen exhaust fans, if they are vented to the outdoors, can lower pollution levels by removing contaminants from the room where the fan is located. Where radon may be a problem, a window should be opened while exhaust fans are in use.

It is particularly important to increase ventilation when you are engaged in activities such as painting or paint stripping, heating with kerosene heaters, cooking with un-vented gas stoves, or participating in hobby or maintenance activities such as welding, soldering, or sanding. You can increase the mechanical ventilation rate by installing heat recovery ventilators (also known as air-to-air heat exchangers). These devices draw outside air into a home and conserve energy by recovering the heat from air that is exhausted to the outdoors. Heat recovery ventilators can be installed in central air systems in new homes or during major remodeling; window units can be installed in existing homes.

Air Cleaners
There are many types and sizes on the market, ranging from tabletop models to whole-house systems. Some are more efficient than others. Air cleaners are generally not designed to remove gaseous pollutants. Air cleaners can be judged on how well they collect pollutants and by how much air they draw through the cleaning or filtering element (expressed in cubic feet per minute). The long-term performance of any air cleaner depends on maintaining it according to the manufacturer's instructions.

At present, the EPA doesn't recommend using air cleaners to reduce levels of radon or its decay products.

Studies show that many times, the dirtiest air we breathe is in our own homes. As we walk through the house, the air turbulence created by our moving bodies stirs up a combination of dust and debris that can be very irritating to the lungs.


Human skin particles, pollen, and smoke are all part of this bothersome brew of irritants. The most irritating are dust mites. Dust mites are microscopic creatures that feed on dust-especially flakes of skin. Examined under a microscope, these little critters make Godzilla look friendly.

Household cleaners and pesticides are full of chemicals. People are even bothered by low levels of these compounds. Ironically, indoor air is now recognized as being full of many of the same chemicals we've spent so much time reducing outdoors. Another important source of indoor air pollution is dry-cleaned clothes, which emit a number of chemicals that may be harmful.


Fortunately, homeowners these days have a wide range of options that can help them breathe more easily and comfortably in the home.

Reducing and Altering Indoor Chemical Use

Pay close attention to the labels on household products. If possible switch to natural products that contain fewer toxic chemicals. When you do need to use a stronger chemical, use it sparingly and follow all the precautions explained on the label.

Air Out Dry-Cleaned Items

Don't immediately store dry cleaned items in a closet. Take the plastic off and allow your clothing to air out for a day or two in a space with good air circulation. Then, recover the items with plastic and store them in a closet.

Use More Sophisticated Furnace Filters

The traditional furnace air filter isn't designed to clean air. Its only function is to keep large particles, like hair and debris, from damaging the furnace blower. These larger particles are rarely the source of human breathing difficulty.

Now there are new, more elaborate filters on the market that trap enough particulate matter to help humans breathe better. In general, the more costly the filter, the more dust it snags out of the airflow. Costing anywhere from $7 to $100, sophisticated filters can pull out up to five times as much dust as traditional filters.

Install an Electronic Air Cleaner

Electronic air cleaners can extract 30 times as much dust as ordinary filters, but they cost a lot more. In fact, a professionally installed air cleaner costs $500 to $700. While this is a substantial amount of money, it's worth every penny if it offers