How often should ducts be cleaned?
Date Published
Every three to five years suits most Mississauga homes. Move to every two to three if you have pets that shed, someone with asthma or allergies, or a finished basement generating a lot of dust.
The interval is a default, though, and four situations override it completely.
After any renovation
This is the one that matters most and the one people miss. Drywall dust is fine enough to travel the entire duct system, and it keeps recirculating for months afterward.
If you have finished a basement, opened a kitchen wall or had any sanding done, clean the ducts after the work — never before, which just means paying to clean ducts you are about to fill. If the work is ongoing, seal the registers in the work area with plastic and tape until the sanding is done.
When you move in
You have no idea what the previous owners did, whether they had pets, or whether the system has ever been cleaned. The house is also usually empty and easy to work in.
It is the single best-timed duct cleaning you will ever book, and it resets the clock so the three-to-five-year interval means something.
When you can see it
Pull a register cover off and look in with a phone light. Loose debris, matted dust on the duct walls, or visible material blowing out when the blower starts are not judgement calls — that is a system that needs cleaning regardless of when it was last done.
After water damage
Any flooding, a burst pipe, or a failed condensate drain that reached the ductwork needs immediate attention, and this is one of the few cases where sanitizing is genuinely warranted rather than an upsell.
A reason that is not a real reason
Annual duct cleaning is not necessary for a normal home, and any company recommending it every year is selling a schedule rather than a service.
Health Canada does not recommend routine duct cleaning as a health measure for a system that is already clean. Be equally sceptical of anyone promising it will cure allergies or asthma — the honest claim is less dust circulating and a blower and coil that are not fighting a layer of buildup.
Dryer vents are on a different schedule
Do not fold your dryer vent into the same interval. It is a fire-safety item rather than a comfort one, and lint accumulates far faster than duct debris.
Annually if you have a long run — six to eight metres with two or three elbows, common in Mississauga townhouses and semis where the laundry sits against an interior wall — or if you run several loads a day. Every two years for a short exterior-wall run in a smaller household.
Quick reference
- Most homes: every 3 to 5 years
- Pets, allergies or a dusty finished basement: every 2 to 3 years
- After any renovation involving drywall or sanding: immediately
- On moving into a home with unknown history: immediately
- After water damage reaching the ducts: immediately, with sanitizing
- Dryer vent, long run or heavy use: annually