Duct-cleaning services often claim that they can improve a home’s air quality and boost the efficiency of its heating and cooling system by sucking or blowing dust and dirt from HVAC system ducts. Some even claim that duct cleaning can improve respiratory health. 

Problem: Duct cleaning actually doesn’t do any of these things. The Environmental Protection Agency reports say in no uncertain terms that duct cleaning has never been shown to prevent air-quality–related health problems…and that the presence of dust and dirt in a home’s ducts has not been shown to increase particulate levels in its air. Studies also have failed to show that duct cleaning improves HVAC system efficiency or reduces home heating or cooling costs. One thing duct cleaning does do well is clean out home owners’ wallets—it can cost between $300 to $1,000 depending on the size of the system being cleaned.

Duct-cleaning services are correct when they say that dust and dirt often lurk in HVAC system ducts. But that dust and dirt tend to remain in ducts, not get blown into the living area of the home. It sounds counterintuitive, but the air flowing through HVAC ductwork typically pushes dust and dirt into the corners of ducts where airflow is too weak to pick it up…and where it doesn’t cause any problems. 

Possible exceptions: Duct cleaning might have health and air-­quality benefits if you smell mustiness when you sniff the air coming from your ducts…or if you see rodent droppings inside your ducts. But even in these cases, duct cleaning is not the main solution—you need to determine how musty air or rodents are getting into your ducts and solve those problems. The most likely explanation is that there’s a gap in your ductwork in a part of your home that smells musty, such as the basement. An energy auditor certified by the Building Performance Institute can perform a duct-leakage test to find these gaps for about $200 (BPIHomeowner.org/find-a-contractor). Repair costs will depend on how much ducting is involved and how accessible it is—prices can range from $400+ for a small ranch house to $2,000+ for a more complicated system in a larger house.