Notice a dusty, musty smell emanating from your air ducts when you turn on the heat? Have them cleaned. Air in U.S. homes is two to five times more polluted than outdoor air, reports the EPA. If your duct system is well sealed and fitted with a high-efficiency filter, a thorough cleaning using brushes and a HEPA (high- efficiency particulate air filter) vacuum can be beneficial. Here’s what you need to know before calling the giant vacuum truck to your home.

Why should I bother?

1 Supply ducts filled with dust, mold, and debris could contaminate indoor air.

2 Dirty return ducts, air-handler fans, and coils could reduce the heating/cooling system’s performance.

3 With effective filtration, ducts shouldn’t need cleaning more than once every five to seven years.

4 Leaky ducts and inefficient filters, typically contaminated with particulates and microorganisms, should be discovered during a routine cleaning.

What do I need to know?

1 Cleaning chemicals, sealers, or disinfectants sprayed into ducts are often pollutants themselves. Ask the cleaner not to use these treatments.

2 Typically, vacuum cleaning alone isn’t enough to remove dirt buildup; however, use of mechanically rotating brushes, the most effective method, can cost four times more.

3 Some duct materials such as ductboard, which is lined with porous fiberglass, are impossible to clean thoroughly. Contamination can return to precleaning levels—often within two months. (EPA, 1998)

4 Residents with allergies, asthma, or chemical sensitivities should vacate their homes during cleaning.

5 Take pets to a safe—and quiet—location during cleaning. Large vacuums may be powerful enough to suck up small animals.

Sources: The Healthy House by John Bower (Healthy House Institute, 2001); EPA Indoor Air Quality site: EPA.gov/appcdwww/iemb/insideiaq.htm