Your home may have caulked windows, doorways sealed to prevent drafts, plus insulation to help keep warm air in and cold air out. All of these can have the cumulative effect of also keeping allergens, fumes, and other lung irritants in the home as well. This is why air cleaners and air purification products are so effective; they treat the trapped air and help circulate fresh air all through the home.
In addition to the purchase of air filtration products, you can also get some expert advice from the American Lung Association in a publication titled, "Improving Indoor Air Quality: A Guide For Homeowners." Pay a visit to lungsusa.org for more information and a link to this important resource for homeowners who want to know more about the dangers of bad air in the home.