EPA studies show that even in the smoggiest cities, the air inside most modern homes is usually at least ten times more polluted than the air outside.
How can this be? There are many reasons, some of which were discovered only recently. They include invisible assassins like radon and CO2, as well as gas-emitting chemicals like formaldehyde used in making modern carpeting, drapery, household cleaners, furniture and building materials. There are also common airborne pollutants such as pollen, viruses, dust and dust mites and damp areas where standing water can breed mold, mildew and other microbes.
