The Inside Scoop.

Having Trouble Breathing? The Problem Could Be Indoor Air

Most people link air pollution with industrial smokestacks or trucks belching clouds of diesel exhaust. But the air we breathe while indoors, where most of us spend 80 to 90 percent of our time, is filled with chemicals and particles that can deliver even higher levels of chemical exposure.

A recent study of residents in both rural and industrial areas confirmed this. It found high chemical levels in the subjects' bodies, indicating they had received doses of pollutants in their homes five to 70 times higher than the highest outdoor levels.

Go to the Source

The best way to improve indoor air quality is to eliminate as many sources of pollution as possible: cigarette smoke, older carpeting, mold and mildew--even hoodless stoves, pressed wood cabinets and burning candles contribute their share. "The sources of pollutants vary greatly, as does the sensitivity of individuals," says Hal Levin, editor and publisher of Indoor Air Bulletin.

Unless you live in a city with unhealthy ozone levels, the next step is to open the windows, or otherwise improve your home's ventilation.

An air filter or cleaning device may be another quick fix. They are most useful in a room with a constant pollution source, or one with limited ventilation. Most only reduce particles in the air, however, and do not eliminate gaseous pollutants.

Mechanical and electric filters may be installed in heating or air conditioning ducts, or used in a portable device with a fan. Basic flat filters can trap large particles, but don't effectively remove small particles, which are easily breathed in. Medium-efficiency filters are typically pleated, woven material made with smaller fibers that can trap the breathable particles without reducing air flow. They are rated at 20 to 50 percent efficiency for removing particles of 0.3 to 10 microns (a micron is one millionth of a meter).

The effectiveness of an air cleaner depends on how well it collects pollutants from indoor air (a percentage efficiency rate) and how much air it draws through the cleaning or filtering element (measured in cubic feet per minute).

High-efficiency filters are rated at 60 to 95 percent efficiency, and are sometimes confused with High Efficiency Particle Arrestance (HEPA) filters, which are defined as being 99.97 percent efficient. Since HEPA filters require powerful fans, they are rarely used in central forced air systems of homes, but are available in portable units. For most homes, upgrading to a medium-or high-efficiency in-duct filter (which cost about $20 to $130) may provide a noticeable improvement.

Filters only work until they become clogged, so pay attention to their performance and change them if you notice a decline. Or you can have an inexpensive pressure gauge installed and change it when the pressure reaches the manufacturer's maximum recommended for the model. As Levin points out, manufacturers' recommendations for changing them are only guidelines; if the air is very dirty, they'll need to be replaced much more often.

Go Electric or Charge It

Electric filters create an electrically charged field or ionize particles to trap them more effectively. Some use electrostatic precipitators, which are charged plates that collect the particles before they are attracted to something else in the room. They were found to be the best filter device by a recent Consumer Reports test. But because of their high cost, the magazine recommended an alternative combination electrostatic/mechanical pleated filter.

Ion generators, available as portable units, also use electrical charges. They work by charging particles in a room, but do not collect them. The particles are then attracted to any nearby surface--walls, floors, furniture or people. These do not improve breathing conditions, as the charged particles are also more attracted to the walls of your respiratory tract.

A few products intentionally produce ozone, which the manufacturers say can improve air by breaking down harmful gases and bacteria. However, ozone is a lung irritant, and although the concentrations from these sources may be low, it is best not to intentionally introduce more into your home. Ozone, a reactive form of oxygen, can also create more harmful chemicals than the ones it breaks down.

Many public health organizations, including the American Lung Association and the California Department of Health Services, warn consumers not to use ozone generators because of ozone's harmful health effects. Electric filters, which may also produce ozone, need to be monitored, particularly if they were not installed or maintained correctly.

Since the effectiveness of filters varies based on airflow, the size of the room and of the particles to be filtered, and how quickly the filtering mechanism needs to be replaced, compare filter efficiencies before investing. CONTACT: EPA's Indoor Air Quality Information Clearinghouse, [phone], www.epa.gov/iaq/iaqinfo.html; National American Lung Association Headquarters, (800)LUNG-USA, www.lungusa.org. The Association of Home Appliance Manufacturers, [phone], www.aham.org, has developed a standard for portable air cleaners. See www.cadr.org for approved devices.

KATHLEEN O'NEIL is a Connecticut-based freelance writer. She spends much of her day breathing.