Clogged Dryer Vent: Warning Signs and Fire Safety

A clogged dryer vent traps hot, lint-filled air inside the dryer and duct, and lint is what catches fire. The clearest early signs are clothes that stay damp after a normal cycle, drying that takes longer than it used to, and little or no air coming out of the outside vent. If you notice any of these, clean the lint screen and vent before running more loads.

Why a clogged vent is a fire risk

NFPA identifies failure to clean the dryer as the leading cause of home clothes dryer and washer fires. The CPSC explains how it happens: lint builds up in the dryer or exhaust duct, blocks airflow, and lets heat build up until, in some dryers, it ignites. CPSC staff add that lint can also collect inside the dryer cabinet even when the lint screen is cleaned after every load, and lint that reaches the heater can start a fire. The U.S. Fire Administration says the risk goes up when the lint filter and vents are not cleaned.

A blocked vent also wears the dryer. CPSC staff note that a blocked duct or lint screen can make the dryer cycle on its high-limit safety thermostat over and over to keep from overheating, often without the owner knowing. That is one reason a thermal fuse can blow; see our dryer thermal fuse guide.

Warning signs of a clogged dryer vent

• Clothes still damp at the end of a normal cycle, or loads that need a second cycle (CPSC).
• Weak or no airflow at the outside vent while the dryer runs (CPSC).
• The outside flap does not open when the dryer is on (USFA, NFPA).
• A hot, humid laundry room during a cycle, or lint collecting around the door seal or lint housing (Whirlpool).
• An airflow or "Check Vent" message on dryers that have one. Whirlpool says this signals restricted airflow from a clogged screen or vent, or a crushed or over-long duct.
• A burning smell while the dryer runs. Treat this as urgent and read what to do if your dryer smells like burning.

Slow drying is often the first and only clue, which is why our guide to a dryer not drying starts with the vent.

What you can safely check yourself

Unplug the dryer before you move it or disconnect anything. For a gas dryer, be careful not to bend or strain the gas connector when you pull the unit out. If you smell gas, do not touch light switches, phones or appliance controls near the smell; leave the house and call your gas utility from outside or from a neighbor's home.

1. Clean the lint screen before or after every load, and never run the dryer without it (USFA, NFPA).
2. Clean behind and around the dryer. USFA and the CPSC both note lint collects behind the dryer; keep the area clear of boxes and clothes.
3. Inspect the duct behind the dryer for kinks, crushing or damage. The CPSC recommends replacing plastic or foil accordion duct with rigid or semi-rigid metal duct, since flexible plastic and foil trap lint and crush more easily.
4. Clear the duct. The CPSC notes you may need to disconnect the duct to remove a blockage. Reconnect it to both the dryer and the outside vent before using the dryer again.
5. Check the outside hood. Make sure the flap opens and clear lint, leaves or nests. Keep snow off it in winter (NFPA). Whirlpool says the hood should be at least 12 inches above the ground or plants.

How often to clean the vent

NFPA recommends cleaning lint out of the vent pipe at least once a year, or sooner if drying is taking longer than usual, and notes you can hire a dryer lint removal service. Whirlpool suggests cleaning the venting every one to two years depending on use, with homes that have pets or dry lots of linty items needing it more often. Long runs that go through a roof or attic are harder to clean yourself and are a good job for a professional.

What correct dryer venting looks like

Dryer exhaust rules come from the dryer maker's installation instructions and the residential building code. The International Residential Code, Section M1502, as adopted by cities such as Seattle, sets these basics, and the manufacturer's instructions control where they set different limits:

Whirlpool echoes the same idea for its dryers: use only 4-inch heavy metal vent, keep the run short and straight, and stay within the vent chart in the installation instructions. A new dryer connected to an old, long or crushed vent can still dry slowly.

When to call a professional

Call for help if the vent is long, runs through a roof, attic or wall you cannot reach, uses plastic or foil duct inside walls, or stays slow after cleaning. Have a pro look at the dryer itself if it overheats, keeps blowing its thermal fuse, or smells hot. NFPA and USFA both recommend professional installation and service, and NFPA advises having gas dryers inspected so the gas line and connection are intact and free of leaks. Our gas dryer repair listings cover that work.

Find local dryer repair companies or washer and dryer repair specialists, or start from your state on the states page. City pages, such as dryer repair in Charlotte, list companies by area.

What vent cleaning costs

HomeAdvisor lists a normal range of about $104 to $188 for professional dryer vent cleaning, with jobs running from about $75 up to $340. It puts repair or replacement of damaged venting at about $80 to $1,000 and rerouting a vent at about $200 to $500. If the dryer needs a part after an overheating event, see our dryer repair cost guide.

If a dryer fire starts

If you see smoke or flames, do not stop to deal with the load. NFPA's home fire guidance is to get out, close doors behind you, stay out, and call the fire department from outside. Do not go back in for anything. Afterward, have the dryer and vent inspected before using them again.