Air ducts should be cleaned as needed as there is no evidence of health benefits from routine cleaning, notes the U.S. Environmental Protection Agency. Have the ducts cleaned if there is evidence of bugs or rodents, mold on hard surfaces, or if dust is released from vents during use.
Duct cleaning providers are not certified by the EPA, but consumers can check with local agencies to learn whether they are licensed. The EPA warns people to be wary of any duct cleaner who either claims the service provides health benefits or attempts to use chemicals. The agency also suggests contacting the references of duct cleaning professionals before hiring them.