Quick answer
The signs of a blocked dryer vent are loads that need two cycles, a dryer top and laundry room that get hot, a burning-lint smell, and an outside vent flap that barely opens while the dryer runs. Stop using the dryer if you smell burning. With a gas dryer, a blocked vent can also push carbon monoxide indoors. Cleaning runs $100–$200.
The signs of a blocked dryer vent show up in the laundry before they show up anywhere else: a normal load that used to dry in one cycle now needs two. A dryer works by pushing hot, wet air outdoors. When lint, a crushed hose or a nest narrows the vent, that air has nowhere to go, the moisture stays in the drum and the heat stays in the machine.
Seven signs your dryer vent is blocked or restricted
- Loads need two cycles, or towels and jeans come out hot but damp.
- The top of the dryer is too hot to rest a hand on, and the laundry room turns warm and humid when it runs.
- A burning or scorched-lint smell. Lint has reached the heater or burner area, so stop the dryer.
- The exterior flap or louvres do not open fully while the dryer is running, or you feel only a weak puff of air outside.
- Lint collects around the door seal, behind the machine or on the wall around the outside hood.
- The dryer shuts off mid-cycle. Its high-limit thermostat or thermal fuse is opening on overheat, and a blown thermal fuse means no heat at all until it is replaced.
- Condensation on the laundry room window or a musty smell: the moisture is ending up in the house.
Why a blocked vent is a fire and carbon monoxide hazard
A blocked dryer vent is a safety problem first and an efficiency problem second. Lint is fine cotton and polyester fibre, it ignites easily, and a restricted vent both collects it and raises the temperature around it. Fire investigators list failure to clean the lint path as the leading cause of clothes dryer fires.
Gas dryers add a second hazard. The burner's combustion products leave through the same vent as the moist air, so a blocked vent spills them into the laundry room, carbon monoxide included. If you have a gas dryer and anyone gets a headache or feels nauseous while it runs, turn it off, open the house up and leave. Ontario's Hawkins-Gignac Act requires working carbon monoxide alarms in any home with a fuel-burning appliance, and a gas dryer counts.
Check this yourself first
- Clean the lint screen, then wash it with dish soap and a brush. Dryer-sheet film can seal the mesh even when it looks clean; water should run straight through it.
- Start the dryer on a heated cycle and go outside. The flap should stand open and you should feel a strong, warm stream of air from a metre away.
- Look into the hood. Lint mats on the louvres, and starlings and sparrows build nests in dryer hoods in spring. A hood with a screen or cage over it will clog with lint: dryer hoods should have a damper flap and no screen.
- Pull the dryer forward and check the transition hose behind it. A hose crushed flat against the wall is a blockage by itself.
- Unplug the dryer before you disconnect anything, and do not move a gas dryer far enough to strain its gas connector.
What a proper dryer vent run looks like
A dryer vent that keeps clogging is usually built wrong. The run should be 4-inch rigid metal duct with smooth walls, joints sealed with foil tape instead of screws that poke into the airstream and catch lint, and a short metal transition hose at the machine. White vinyl or thin foil flex hose inside a wall or ceiling sags, holds lint and should be replaced.
Length matters as much as material. Every dryer's installation manual gives a maximum equivalent vent length, and each elbow counts as several feet of straight pipe against it. Houses with second-floor laundry rooms, common in 2000s and newer subdivisions, often have long runs through the joist space to a side wall or up to the roof, with two or three elbows. Those runs clog faster and need cleaning every year instead of every few years.
Condo and townhouse dryers sometimes vent through a booster fan or a secondary lint trap in the ceiling. Both need their own cleaning, and a failed booster fan produces every sign on the list above. In a condo, ask the property manager which parts of the run are yours before booking.
Call now if, and what dryer vent cleaning costs
- You smell burning lint or see scorch marks on the lint screen housing or the hose.
- A carbon monoxide alarm sounds while a gas dryer is running.
- The dryer cabinet is too hot to touch or it trips off on every load.
- The vent run is in a ceiling or wall you cannot reach and the outside flap does not move.
- Dryer vent cleaning: $100–$200, booked alone or added to a duct cleaning.
- Whole-house duct cleaning for a typical detached home: $300–$700.
- Rerouting or replacing a vent run: quoted in writing after we see the route, since length and access set the price.
A proper cleaning brushes and vacuums the whole run from the hood back to the machine and ends with an airflow check at the flap. Book dryer vent cleaning by itself or with a duct cleaning visit. A vent that is too long, crushed or made of vinyl gets a quote for a new dryer vent run, and gas dryer connections fall under the CSA B149.1 gas code, so ZK Mechanical's TSSA-licensed technicians handle them.
Contact ZK Mechanical to book from Burlington, Oakville, Milton, Hamilton or Mississauga. Pricing details are in what dryer vent cleaning costs, and related questions sit under air quality and ducts.