Dryer vent safety

Every load of laundry sends hot, damp air and lint out of the dryer, through a duct, and out of the house. When lint builds up in that path, the dryer runs hotter and longer, and it can overheat and start a fire [2]. The U.S. Fire Administration lists failure to clean as the leading factor in clothes dryer fires, at 31 percent [1].

The good news is that most of the fix is routine cleaning and the right kind of duct. This guide covers the warning signs, what you can clean yourself and when to call a professional. For pricing, see dryer vent cleaning and repair cost.

Signs your dryer vent is clogged

Clothes take longer to dry, or are still damp at the end of a normal cycle. The Consumer Product Safety Commission says this may mean the lint screen or the exhaust duct is blocked [2].
The flap on the outside vent doesn't open when the dryer is running [3].
Little or no air comes out of the outside vent. With the dryer running, hold your hand under the outdoor vent hood. You should feel a strong flow of warm air [4].
Lint collects around the outside vent or behind the dryer.
The duct behind the dryer is crushed, kinked or pulled loose [3].

If you ever smell something burning, stop the dryer, unplug it if you can do so safely, and don't use it again until the vent is checked. If there's smoke or fire, get out and call 911.

Clean the lint screen every load

Clean the lint screen before or after every load [2]. The U.S. Fire Administration goes further and recommends before and after each cycle, and never running the dryer without the screen in place [3].

Every so often, also:

Pull the screen and vacuum the slot it sits in.
Clean behind and under the dryer, where lint builds up too [3].

Clean the vent

The CPSC recommends cleaning the dryer vent and exhaust duct periodically [2]. Your dryer's manual says how. For a short, straight vent through a wall, many homeowners can do it themselves:

Unplug the dryer. If it's a gas dryer, have a professional move it and disconnect it. The gas connection should be handled by someone qualified [3].
Pull the dryer out gently and loosen the clamp holding the duct to the back of the dryer.
Clean the duct from both ends with a vacuum or a dryer vent brush kit, then clean the opening on the back of the dryer.
Go outside and clean the vent hood. Remove lint from the flap and the opening, and make sure the flap swings freely.
Reconnect the duct with clamps. Don't use screws that poke into the duct, because they catch lint, and don't use duct tape [4].
Test it. Run the dryer for 5 to 10 minutes and feel for strong airflow at the outside hood [4]. Reconnect anything you disconnected before you use the dryer again [2].

Hire a professional dryer vent cleaner when the vent is long, has several bends, runs through the attic or ends on the roof. A vent that ends on the roof is hard to reach safely.

Why plastic and foil hoses should go

Many dryers are still hooked up with the white plastic or crinkly foil accordion hose sold at hardware stores. The CPSC warns that these hoses trap lint more easily and kink or crush, which can greatly cut airflow. It recommends replacing them with rigid or semi-rigid metal duct [2].

Dryer makers say the same. Whirlpool's installation instructions call for a 4-inch heavy metal vent and state: do not use a plastic vent, and do not use a metal foil vent. Flexible metal duct is allowed only if it can be reached for cleaning, and that model's instructions limit it to 7¾ feet total [4]. LG also says to avoid plastic or vinyl ducting [5].

If your laundry area has a vinyl or foil dryer hose, replacing it is one of the simplest safety upgrades in the house.

How a dryer vent should be set up

Use your dryer's installation instructions as the rule, since requirements vary by brand and model. Common requirements from the manufacturers' instructions:

Part of the vent	What to look for
Duct material	Rigid or semi-rigid metal, usually 4 inches across [2, 4]
Length	As short as possible. Every bend reduces the allowed length [4, 5]
Bends	Few. LG allows no more than four 90-degree elbows [5]
Shape	Straight or a gentle curve, not kinked, crushed or dented [5]
Connections	Clamps, not screws or duct tape [4]
Where it ends	Outdoors, never into a wall, ceiling, attic, crawl space or chimney [4]
Outside hood	A louvered or box-style hood that opens freely, at least 12 inches above the ground. Whirlpool says not to use a hood with a magnetic latch [4]

The maximum length depends on the dryer and on the number of bends. For example, LG lists a 65-foot maximum for a straight run of 4-inch rigid duct, with 6 feet less for each added elbow [5]. Whirlpool's table for one of its dryers runs from 64 feet with no elbows down to 27 feet with four, depending on the hood [4]. A vent that's too long for your dryer, or one with too many turns, may need to be rerouted.

A few setups to fix:

A screen or grate over the outside opening. It catches lint and clogs. A dryer vent needs a flap, not a screen. See dryer vent cover grate.
A vent that ends in the garage, attic or crawl space. That puts lint and damp air inside the house. A dryer that vents into the crawl space adds moisture that can lead to mold and rot [6]. See vapor barrier vs. encapsulation for more on crawl space moisture.
A duct that's come loose behind the dryer. Reconnect it with clamps.

Other dryer safety habits

Have the dryer installed and serviced by a professional [3].
Plug the dryer directly into a wall outlet. Never use an extension cord with a major appliance [1].

Many vent problems show up during a home evaluation, from a dirty dryer vent to a bad hookup. If the dryer itself is the problem, see the appliance guides.

HomeCloud is a licensed general contractor. We evaluate homes and price and do the repairs, including dryer vent work.