I keep hearing Air Duct and Vent Cleaning commercials on the radio. Clearly it is a big business.  They brush and vacuum up each air duct and into each return where possible.  It is supposed to help remove dust, mold, etc especially helpful for people with allergies.

American Lung Association states:

“Duct cleaning has not been shown to prevent health problems, nor is scientific evidence currently available to conclusively demonstrate that particle (e.g., dust) levels in homes increase because of dirty air ducts. The U.S. Environmental Protection Agency does not recommend that air ducts be cleaned routinely, but only as needed.”

They also have tips for improving Air Quality.

Be sure to read Fixing Leaky Ducts – Reducing Air Leaks