The American Lung Association also said that heating, ventilation and air conditioning systems are a frequent source of the indoor air pollution that can aggravate asthma.

Ductz Indoor Air Professionals, in Ann Arbor Mich., suggest ways to reduce home's asthma triggers and improve the indoor air quality. They recommend:

-- Do not smoke indoors. The U.S. Environmental Protection Agency says secondhand smoke is particularly dangerous to those who suffer from asthma.

-- Keep the home dust-free. When dusting, the EPA suggests using a damp cloth and making sure all allergy and asthma sufferers have left the area.

-- Have heating, ventilation and air conditioning systems inspected and, if necessary, cleaned.