How to clean a dryer vent before it starts a fire

Towels now take two cycles, the top of the dryer is hot, and the laundry room smells faintly scorched. The lint screen is clean, so it looks like the dryer is wearing out. It usually is not. The lint that gets past the screen packs the duct behind the dryer and the pipe through the wall, and both NFPA and the U.S. Fire Administration name failure to clean the dryer as the leading cause of dryer fires. Fall is when a dryer goes back to daily use, so clear the whole run now, before the first cold week.

Check the outside vent while the dryer runs

Start an empty air-only cycle and go outside to the vent hood. The flap should lift and you should feel a steady push of warm air. A flap that barely moves, or a hood packed with gray fuzz, confirms the duct is blocked and not the dryer. Pull the lint out of the hood by hand, and check that the flap is not painted shut, taped over, or covered by a screen that catches lint.

Unplug the dryer and pull it away from the wall

Switch the dryer off, then unplug it. For a gas dryer, turn the gas shutoff valve on the supply line to the closed position before you move anything, and do not stretch or kink the flexible gas connector. Walk the dryer forward far enough to reach the duct clamp behind it. Vacuum the floor and the back panel of the dryer, where lint collects around the exhaust outlet.

Disconnect the duct and clear both ends

Loosen the clamp or tape holding the short transition duct to the dryer outlet, then the clamp at the wall. Take the duct outside and shake or brush out the lint. Reach into the dryer exhaust outlet with a vacuum crevice tool and pull out what you can. If the transition duct is white plastic or thin foil, throw it out and replace it with rigid or flexible metal duct, which NFPA recommends for proper airflow. Foil and plastic trap lint and crush flat behind the dryer.

Brush the wall duct through to the outside

Feed a dryer vent brush, or a vacuum hose with an extension, into the wall opening and work it toward the outside hood. Long runs need a brush kit with screw-together rods, sold by hardware stores. Push in, twist, pull back, and clean the brush each time until it comes out clean. Go outside and pull out any lint the brush pushed to the hood end.

Reconnect the duct and test the airflow

Fit the transition duct back onto the dryer outlet and the wall pipe with the clamps tight, keeping the run as short and straight as the space allows. Slide the dryer back without crushing the duct, then plug it in and reopen the gas valve if you closed one. Run the empty cycle again and confirm the outside flap now opens fully and the air is warm and strong. Clean the lint screen before or after every load from here on, and repeat the full clearing once a year, or sooner if drying times climb again.

If that fails. If the flap still barely opens after the duct is clear, the blockage is in a section you cannot reach, such as a run through a ceiling or a crushed pipe inside a wall. Book a dryer vent cleaning service rather than running the dryer on a partial vent.

If you smell gas. Stop, do not plug the dryer back in, leave the house, and call the gas utility from outside. A gas dryer's line and connection should be checked by a qualified technician, and any fitting you disturbed needs a leak test before the dryer runs again.

Sources. U.S. Fire Administration clothes dryer fire safety flyer, NFPA clothes dryer safety tip sheet.