Dryer vent cleaning: how often, and how to do it

The short answer

NFPA's dryer safety tip sheet says the leading cause of home clothes dryer fires is failure to clean them. Its schedule is simple: clean the lint filter before or after each load, and once a year, or more often if drying is taking longer than normal, clean lint out of the vent pipe or have a dryer lint removal service do it. The U.S. Fire Administration's flyer says to clean the lint filter before and after each cycle and never to run the dryer without one.

The lint filter catches most of it, but not all. The rest settles in the duct behind the dryer and in the vent to the outside, where you can't see it building up. CPSC explains why that matters: lint blocks the airflow, heat builds up, and in some dryers that can start a fire.

Signs the vent is clogged

• Longer drying timesCPSC says clothes still damp at the end of a normal cycle, or loads that need longer than usual, may mean the lint screen or the exhaust duct is blocked.
• No air at the outside ventWith the dryer running, go outside and feel the vent. CPSC says if exhaust air isn't escaping, the vent or duct may be blocked.
• A flap that stays shutNFPA and USFA both say the outdoor vent flap should open while the dryer runs. In winter, NFPA adds, check that snow isn't covering it.
• Lint behind the dryerUSFA and CPSC both say to clean behind the dryer, where lint builds up. A lot of it there is worth a closer look at the duct connection.

The duct matters: metal, not foil or plastic

CPSC says to replace plastic or foil accordion-type duct with rigid or corrugated semi-rigid metal duct, and notes that most dryer makers specify one of those. Metal gives the most airflow. The flexible plastic or foil kind traps lint more easily and kinks or crushes, which cuts airflow a lot. NFPA likewise says rigid or flexible metal venting should be used. Keep the run as short and straight as your laundry room allows. Your dryer's installation instructions give the maximum duct length for your model.

USFA also says to check the venting behind the dryer to make sure it isn't damaged, crushed or restricted. Pushing the dryer back against the wall is a common way to flatten a duct without noticing.

How to clean a dryer vent

1. 1. Unplug it, and shut off the gasUnplug an electric dryer. For a gas dryer, close the gas valve behind it before you move it, and be gentle with the gas line.
2. 2. Pull the dryer out and disconnect the ductSlide the dryer away from the wall and loosen the clamp holding the duct to the back of the dryer. CPSC notes that clearing a blockage may require disconnecting the duct.
3. 3. Clean the lint filter and its slotRemove the filter, clean it, and vacuum the slot it sits in as far as the hose reaches.
4. 4. Brush the duct from insideFeed the brush into the wall vent, adding rods as you go, and turn it in the direction the kit says. Pull out lint and vacuum it as it comes loose.
5. 5. Clean the outside hoodGo outside, clear lint from the hood and make sure the flap swings freely. Brush in from this end too if the run is long.
6. 6. Check the duct and reconnectReplace foil or plastic duct with metal, and replace any section that's crushed. Reconnect it to the dryer and the wall vent, as CPSC reminds, before you use the dryer again.
7. 7. Run it and check the airflowPush the dryer back without flattening the duct, run it on air or low heat, and feel for strong airflow at the outside vent.

Inside the dryer

Lint also gathers inside the cabinet, around the drum and the heater. NFPA says to remove lint that has collected around the drum, and CPSC suggests having a qualified service person clean the inside of the dryer chassis periodically. That is a job for a technician, not a screwdriver and a vacuum, especially on a gas dryer.

When to hire a pro

Call a dryer vent cleaning service if the vent runs a long way, goes up through the roof, has several bends, or is hidden in a wall or ceiling where you can't reach both ends. Do the same if cleaning didn't fix slow drying, or if the duct is foil or plastic and needs replacing in a tight space. For gas dryers, NFPA says to have a qualified professional inspect the gas line and connection to make sure they're intact and free of leaks. USFA and NFPA both say to have the dryer installed and serviced by a professional.

Everyday habits that help

NFPA also says not to overload the dryer, to keep boxes, cleaning supplies and clothes away from it, and to turn it off if you leave home or go to bed. Clothes soiled with gasoline, oils or other flammable substances need special care: CPSC suggests washing them more than once and hanging them to dry.

Questions people ask