Dryer Vent Safety and Lint Fires

A clothes dryer pushes hot, damp air loaded with lint through a duct to the outside. Most of the lint stays in the lint screen. Some does not, and it collects in the dryer housing, the duct and the outside hood. Lint is made of fibre and burns readily, and a restricted duct makes the dryer run hotter. That combination is why fire services and manufacturers repeat the same advice about cleaning, and why a slow dryer is worth taking seriously.

What the fire data say

The most detailed published breakdown of dryer fires comes from the U.S. Fire Administration. Its report on clothes dryer fires in residential buildings (2008 to 2010) estimated about 2,900 such fires reported to US fire departments each year, causing an estimated 5 deaths, 100 injuries and $35 million in property loss annually. Failure to clean was the leading factor contributing to ignition, at 34%. Dust, fibre and lint (28%) and clothing (27%) were the leading items first ignited. Fires were more frequent in fall and winter, peaking in January.

The USFA's current appliance safety page gives a more recent figure: failure to clean was the leading factor in home clothes dryer fires from 2018 to 2020, at 31%. These are US figures, but the physics of a lint-filled duct are the same in an Ottawa basement.

Signs your dryer vent may be restricted

Long drying times with heat. Whirlpool's product help states that if a dryer is heating but still has long dry times, the likely cause is a vent issue or restricted airflow. See dryer taking too long.
A hot dryer or hot laundry room. The top of the dryer, the clothes or the room are hotter than usual. See dryer overheating.
The dryer shuts off early or a thermal fuse blows, which can happen when the dryer overheats. See dryer shuts off.
The outside hood flap does not open when the dryer is running, or little air comes out.
Lint collects around the door opening, behind the dryer or around the outside hood.
A burning or scorched smell. Stop the dryer. See the section on what to do below.

Our problem guide on a clogged dryer vent covers the symptoms in more detail.

What you can safely do yourself

Every load

Clean the lint screen before or after every load. The City of Toronto, the Town of Oakville fire department, Consumer Reports and Natural Resources Canada all give the same advice. Oakville's fire department adds: never run the dryer without the lint filter in place.

Every month or so

If you use dryer sheets, the screen can clog with a film that you cannot see. Natural Resources Canada suggests scrubbing the lint filter with a toothbrush about once a month in that case. Rinse and let it dry fully before putting it back.

Outside, especially in winter

Check that the outside hood flap moves freely and is not blocked. Whirlpool says exhaust hoods must be at least 305 mm (12 in) from the ground or anything that could obstruct the exhaust, including snow. In Ottawa and Gatineau winters, a snowbank or ice around the hood can block it within a day. Clear it gently by hand; do not use a sharp tool on the flap.

Behind the dryer

With the dryer unplugged (and, for a gas dryer, without touching the gas line or connector), look at the duct between the dryer and the wall. It should not be crushed, kinked or pushed flat against the wall. Vacuum lint from the floor behind the dryer.

Vent materials and layout

Whirlpool recommends 4 in (102 mm) heavy metal exhaust vent, rigid or flexible metal, and says aluminium foil or plastic vent is not recommended because it can collapse or be crushed. The City of Toronto's fire safety page gives the same advice: rigid or flexible metal ducting to the outdoors, because plastic or foil ducts are more prone to kinking, sagging and crushing. Consumer Reports suggests replacing accordion-style ducts with rigid metal.

Length and elbows matter. Whirlpool notes that increased length and elbows reduce airflow and encourage lint build-up, and that vent runs should not exceed the lengths in the dryer's vent system chart, which is specific to each model. InterNACHI's life expectancy chart puts a plastic dryer vent at about 5 years and a steel one at about 20.

In condos, townhouses and stacked laundry closets, the duct run is often long, or hidden in a wall or ceiling. That is where a full-length clean needs proper equipment, and where an owner check cannot see the whole duct.

How often to clean the duct

Whirlpool says the venting from the dryer to the outside must be cleaned every one to two years, or whenever drying performance drops. Consumer Reports recommends at least once a year, using a brush made for dryer ducts. A large household running the dryer daily will need it more often than a single person running it twice a week.

Habits that lower the risk

Turn the dryer off if you leave home or go to bed (City of Toronto).
Keep the area around the dryer clear of things that can burn.
Do not dry fabrics soaked with oils, chemicals, gasoline, wax or solvents, including cleaning rags. The City of Toronto lists vegetable oils among these.
Do not overload the dryer. Natural Resources Canada notes that overfilling reduces airflow and strains the motor.
Have working smoke alarms on every storey, and a carbon monoxide alarm if you have a natural gas or propane dryer (City of Toronto).

Gas dryers: two extra points

A gas dryer vents combustion products as well as damp air, so a blocked or disconnected duct matters for more than drying time. The City of Toronto's fire safety advice is to install a carbon monoxide alarm if you use a natural gas or propane dryer. Do not move a gas dryer to clean behind it if that would strain the gas connector; ask a technician. RepairWell diagnoses gas dryers, and any work on the burner, igniter, valve or gas connection is done by a certified gas contractor we work with.

If you smell burning or see smoke

Stop the dryer. If there are flames or smoke you cannot account for, get everyone out and call 911 from outside. Samsung's Canadian support advice is that if an electric dryer is smoking, turn it off; if a burning smell continues, turn the dryer off at the circuit breaker and request service. If a gas dryer is smoking or you smell gas, leave the building and call emergency services without touching switches. Our appliance emergency page has the gas utility numbers for Ottawa and Gatineau.

A new dryer can give off a burning smell on its first runs as oil residue burns off; Samsung suggests running it empty for about 15 minutes. That does not apply to a dryer that has been in use for months.

What a technician checks

When we diagnose a dryer that overheats, shuts off or takes too long, airflow is one of the first things checked, because a restricted vent can make a new part fail the same way the old one did. Lint that has built up inside the dryer housing, around the blower and near the heater is technician territory: it means removing panels, and on a gas dryer it sits near the burner, which is work for the certified gas contractor we work with. The written finding says whether the vent needs attention and whether it is within reach of a standard clean. RepairWell's diagnostic is $89, waived if you go ahead with the repair.

Questions

How often should you clean a dryer vent?

Whirlpool says every one to two years, or when drying performance drops; Consumer Reports says at least once a year. Clean the lint screen on every load and check the outside hood more often in winter, when snow can block it.

Can a dryer catch fire from lint?

Yes. The U.S. Fire Administration found failure to clean was the leading factor contributing to ignition in residential dryer fires, and dust, fibre and lint were among the leading items first ignited. A restricted vent also makes the dryer run hotter.

What are the signs of a clogged dryer vent?

Clothes take much longer to dry even though the dryer heats, the dryer or room gets hot, the outside flap barely opens, lint collects around the door or hood, or the dryer shuts off early. Any burning smell means stop the dryer.

Is foil or plastic dryer vent safe?

Manufacturers and fire services advise against it. Whirlpool recommends 4 in (102 mm) rigid or flexible metal vent and says foil or plastic can collapse or be crushed; the City of Toronto gives the same advice.

Is it safe to run the dryer when no one is home?

Fire safety advice from the City of Toronto is to turn the dryer off if you leave home or go to bed. A fire that starts in an empty house has longer to spread before anyone notices.

Why is my dryer taking two cycles to dry?

A restricted vent is one common cause, especially if the dryer is producing heat. Other possibilities include a faulty heating part, a worn moisture sensor or overloading. If the vent is clear and the problem continues, book a diagnosis.

Dryer vent safety and lint fires