The Real Rule: Inspect Yearly, Clean When Needed
The EPA's guide says ducts should be cleaned only as needed, not routinely. NADCA, the duct cleaning industry's association, recommends inspecting the system once a year and cleaning when the inspection finds a reason. Both point to the same habit: look first, then decide.
A yearly look takes a flashlight at one supply register and one return, or a camera inspection for the runs you can't reach.
Homes That Need Cleaning Sooner
| Factor | What it adds to the ducts | What to do |
|---|---|---|
| Shedding pets | Hair and dander in the returns | Check the return grilles every few months |
| Renovation or new construction | Drywall and sawdust | Inspect once the work ends |
| Water leak or flooding | Moisture that feeds mold | Inspect right away |
| Rodents or insects | Droppings and nesting | Clean after the pests are gone |
| Smoking indoors | Residue in duct dust | Inspect for odor and buildup |
Signs It's Time Now
- Dust puffs out of the supply registers when the system starts
- Visible mold inside the ducts or on the coil
- Droppings, nesting material or insects in the runs
- A filter that clogs much faster than it used to
Those match the EPA's reasons to clean. Whether the cost is justified is covered in is air duct cleaning worth it, and the season to book in is covered in the best time of year to clean ducts.
The Dryer Vent Runs on a Different Clock
The dryer vent is a fire-safety job, not an air-quality one. The U.S. Fire Administration reports that failure to clean was the leading factor in home clothes dryer fires from 2018 to 2020, at 31 percent. Clean the lint screen every load and get the vent line checked when drying slows down, which happens faster on long townhome runs.