Studies conducted by the Environmental Protection Agency have shown that the air within our homes and other buildings can be more seriously polluted than the outdoor air in even the largest and most industrialized cities. And because most people spend as much as 90 percent of every day indoors, this can spell trouble, especially for children, seniors and people burdened with respiratory or cardiovascular disease.

As houses have become more energy-efficient, with less room for air to escape, particles and gases become trapped inside, explained Dr. Mahmoud Effat, a board-certified allergist and immunologist based in Exton.

The list of pollutants that can become trapped in homes is extensive, from remnants of the chemical, perchloroethylene, also known as perc, emanating from newly dry-cleaned clothes, to radon, cigarette smoke, pesticides, aerosol sprays, pet dander, dust, mold and even airborne particles generated from a wood-burning fireplace. The ramification of each pollutant varies, from mild discomfort to serious illness and sometimes even death.

"(And) the incidence of allergy and asthma has been increasing," he added. For people with allergies and asthma, indoor air pollutants such as dust, mold and mildew can be a major source of discomfort. Although seemingly similar in symptoms to that of a cold, allergy symptoms usually last for longer periods of time and are not as severe.

According to Kevin Stewart, director of Environmental Health for the American Lung Association of Pennsylvania, the first line of defense in minimizing the effect of mold spores, dust mites, pet dander and other allergens is source control.

Combustion in the home is another potent air pollutant. "Any time you are burning something, you are making exhaust components of whatever (you are burning). From the heat comes carbon monoxide, a lung asphyxiate, which grabs a hold of hemoglobin (in the blood) so the blood is not able to carry oxygen."

Carbon monoxide is a colorless, odorless gas. Gradual exposure over a long period of time can cause flu-like symptoms, headache and nausea. Stewart recommends a three-prong approach to safeguard against carbon monoxide.

First, don’t run a car or lawn mower in a closed garage. Second, routinely maintain heating systems, whether oil, gas, coal or wood. Finally, install a carbon monoxide monitor in the house, preferably in the primary sleep area.

Stewart urges using wood fireplaces sparingly, only for heat and not esthetics. Another area of concern to the American Lung Association is air toxins. Pesticides, cleaning solvents such as floor and tile cleaners, hair spray, nail polish and nail polish remover all affect air quality.

Air filters can also help further the cause of fresh indoor air by removing small particles from the air. Dr. Effat recommends HEPA or 3M furnace filters. He prefers the disposable type of filter in lieu of the permanent washable variety.

"You can not wash everything out of everything." And don’t forget to circulate fresh air throughout the house from time to time, Effat added. Something as simple as opening the windows a crack for half an hour a day in nice weather can have a measurable impact on the quality of indoor air. Letting fresh air in will help the house to breath.