Clothes dryers are a well-documented cause of house fires, and the leading factor, according to both the National Fire Protection Association and the U.S. Fire Administration, is failure to clean them. Lint is light, dry and highly flammable, and a dryer moves hot air through it for an hour at a time. The lint screen catches most of it. What gets past the screen collects in the duct behind the dryer and in the duct that runs to the outside wall, and that is where fires start.
A clogged vent also makes every load take longer and wears out the dryer's heating element and motor. Once a year, before the heavy laundry season of fall and winter, is a sensible time to look at the whole path from the drum to the outside wall. This guide covers what to look for, what you can safely do yourself, and what a vent cleaning service does.
Signs the vent is blocked
A dryer with a blocked vent tells you, if you know what to listen for. The NFPA's tip sheet flags longer drying times as the main warning sign. The others are easy to check in one load.
- A normal load of towels takes more than one cycle, or clothes are still damp at the end.
- The top of the dryer and the laundry room are noticeably hot while it runs.
- A burning smell during a cycle.
- The outside vent flap barely opens, or does not move at all, while the dryer runs.
- Lint collecting on the floor behind the dryer or around the outside vent hood.
- The dryer shuts off mid-cycle or shows an airflow or vent error code (newer models have a sensor for this).
What you can safely do yourself
The homeowner part is the lint screen, the area you can reach by hand, and the outside vent hood. None of it involves disconnecting the duct from a gas dryer or moving a dryer that is hooked to a gas line, which is a job for a technician.
- Clean the lint screen before every load. Once a month, wash it with warm soapy water and let it dry fully; dryer sheet residue clogs the mesh and cuts airflow.
- Vacuum the lint screen slot with a crevice tool and wipe lint from around the drum opening and the door seal.
- Go outside and find the vent hood. Clear leaves, lint and any bird nest from the flap, and confirm the flap swings open freely when the dryer runs. Remove any screen someone added over it; screens trap lint and are not allowed by most dryer manufacturers.
- Look at the duct behind the dryer without moving it. If you see white vinyl or thin foil, note it: both NFPA and the USFA say the duct should be rigid or flexible metal, and the old plastic type should be replaced.
What a professional vent cleaning includes
A dryer vent service or appliance technician cleans the path you cannot reach: inside the dryer cabinet, the transition duct behind it, and the full run of duct through the wall, floor or attic to the outside. Long runs with several elbows, or runs that go up through a roof, collect the most lint and are the hardest to clear without the right brushes.
The visit usually takes under an hour on a straight run and longer on a long or complicated one. Ask them to show you what came out, and to tell you how long the run is and how many turns it has; that determines how often it needs doing.
- Pull the dryer out, disconnect the transition duct, and vacuum lint from inside the dryer cabinet around the blower and heating element.
- Run a rotary brush through the entire duct from the dryer end and from the outside hood, with a vacuum catching what comes loose.
- Replace a plastic or foil transition duct with semi-rigid or rigid metal, and replace crushed or kinked sections.
- Check the outside hood, replace a damaged flap, and remove any screen.
- On a gas dryer, check that the gas connector is intact and leak-free after moving the dryer back.
How often, and what changes the schedule
Once a year is the baseline that the NFPA gives, with more frequent cleaning if drying times are getting longer. Several things push a house toward twice a year or more.
- A long duct run, more than a few elbows, or a run that goes up through the roof instead of straight out a wall.
- A large household or a lot of towels, bedding and pet hair, or any history of the vent being blocked before.
Other dryer fire safety habits
The vent is the biggest item, but the NFPA and USFA tip sheets include a few more habits that cost nothing. Keep the area around the dryer clear of boxes, cleaning supplies and clothes, and never run it when you leave the house or go to bed. Items that have touched gasoline, cooking oil or solvents should be laid outside to air out before washing and should not go in the dryer until washed. Foam-backed rugs and anything with rubber should air dry. Do not overload the drum. And have the dryer installed and serviced by a professional, especially a gas dryer, where the connection behind it should be checked whenever it is moved.
Questions people ask
My vent looks clean from outside. Does it still need cleaning?
The hood is the easy part to see and the last place lint collects. Most buildup is in the elbows and the horizontal run inside the wall or attic. If drying times are longer than they used to be, the run needs clearing regardless of what the hood looks like.
Can I clean the duct myself with a brush kit?
On a short, straight run to an electric dryer that you can pull out easily, a drill-powered brush kit works for many people. On a gas dryer, a long run, or a run through the roof, a service is safer and more thorough.
Is the vinyl duct behind my dryer really a problem?
Yes. Thin plastic and foil ducts trap lint in their ridges, crush easily behind the dryer, and can burn. Both the NFPA and the USFA say to use rigid or flexible metal duct. Replacing the transition duct is a quick job for a technician.
Sources
- U.S. Fire Administration: Appliance and electrical fire safety www.usfa.fema.gov
- U.S. Fire Administration: Clothes dryer fire safety flyer (PDF) www.usfa.fema.gov
- NFPA: Clothes dryer safety tip sheet (PDF) www.nfpa.org