Regular cleaning of home air vents isn't recommended by the Environmental Protection Agency, although cleaning is recommended if mold is visible in the ducts or if dust is projected from the ducts. Cleaning also is recommended if the ducts are infested with insects or vermin.
If these conditions are present, homeowners must determine the cause of the problem before cleaning the ducts because the situation is likely to recur. Insulated ducts that show mold can't be adequately cleaned and must be replaced. The EPA cautions homeowners to investigate potential duct cleaning companies thoroughly because improper cleaning techniques can release contaminants into the home.