A breath of fresh air: home ventilation made simple. (House & Home).

On a blistering cold day, with the house tightly sealed and the heating cranked up, the air at home may pose more of a threat to human health than smoggy urban air.

Environmental Protection Agency (EPA) studies indicate that indoor levels of pollutants may be two to five times--and occasionally more than 100 times--higher than outdoor levels. And a pollutant released indoors is 1,000 times more likely to reach a person's lungs than one released outdoors, according to the World Health Organization (WHO).

While the highest indoor air pollution exposures occur in developing countries, well-insulated American homes are not immune to the problem. Although tightly sealed homes have reduced the use of fuels, they have also wreaked havoc with Americans' respiratory systems, says Cherylee Darneille, a registered nurse with the American Lung Association.

Inadequate ventilation can increase indoor pollutant levels by not bringing in enough fresh air to dilute emissions from indoor sources, says Darneille. High temperature and humidity can also increase concentrations of some pollutants.

Dry-cleaned clothing, chlorinated water, tobacco smoke, pressed wood products, insulation, adhesives, foam, lubricants, plastics, carpets and household cleaning products can off-gas pollutants, says the EPA. Other potential sources are visitors from outside, such as pesticides and mold. Indoor air pollutants include carbon monoxide, formaldehyde, asbestos and lead, many of which are part of a class of chemicals known as Volatile Organic Compounds (VOCs) that evaporate quickly at room temperature.

"Pollutants can be really troublesome for people with allergies," Darneille says, adding that short-term exposure might cause headaches and dizziness. Long-term exposures can result in respiratory disease, heart disease and cancer. Luckily, there are simple things people can do to improve their air, according to Michael Lamb, a Department of Energy certified energy specialist.

Seal and Ventilate

When it's cold, rainy or swelteringly hot, opening windows for fresh air is not energy efficient. Lamb's motto for achieving healthy indoor air quality is "seal tight, ventilate right."

Rob Watson, senior scientist and green building expert at the Natural Resources Defense Council (NRDC), says inadequately sealed ductwork can cause higher energy bills and deposit dust back into the home. "Windows need to be airtight and should have thermal breaks and no condensation. Enemy number one of indoor air quality is moisture," he says.

Moisture spurs mold growth, which is an adversary of respiratory systems. Watson encourages residents to leave windows open when showering or cooking, He says, "A more effective tactic is using bathroom and laundry room fans, which can be set to timers." Lamb adds, "Even better, attach a humidistat that will automatically turn the fan on when moisture reaches a specific level. Undisturbed dampness can cause serious mold problems. You won't die, but you may wish you were dead."

Watson says enemy number two to indoor air quality is inadequate ventilation for stoves. "Range hoods over gas stoves should be vented to the outside, and all wood-burning heaters and fireplaces should have a dedicated fresh air supply."

Use Common Sense

When dealing with ventilation, bigger is not necessarily better. "People often buy air conditioners too large for their homes and end up with soaking wet ducts" says Lamb. He also points out that "monster-sized fans can cause back drafting, which might draw radon and other nasty elements from around the foundation into the house."

Lamb says, "If you smell something strange, shut off your heating or cooling system, and open windows." There should also be a complete renewal of the home's air supply every three hours to meet the standard for healthy indoor environments. Most homes rely on mechanical ventilation for this.

"Heat Recovery Ventilators (HRVs) introduce fresh air and direct 80 percent of the energy back into the system," says Watson. Benefits are two-fold--lower energy bills and increased comfort.

To determine your home's energy and ventilation fitness, Watson suggests contacting a state energy office or a home energy doctor. Do-it-yourself test kits for some pollutants are available at major stores and EPA offices, says Darneille. By applying energy-saving techniques and introducing fresh air, all of a building's occupants should be able to breathe a little easier. CONTACT: American Indoor Air Quality Council, [phone], www.iaq council.org; Home Ventilating Institute, [phone], www.hvi.org.

DIANE M. MARTY enjoys fresh air in Littleton, CO.