How often should you clean your dryer vent / exhaust duct?

Failure to clean is the leading factor in home clothes dryer fires.

The US Fire Administration estimated 2,900 clothes dryer fires in US homes a year in its 2008 to 2010 study, and found failure to clean was the leading factor in how they started, at 34 percent. Well before that point, a restricted duct makes the dryer run longer per load: the Consumer Product Safety Commission lists clothes still damp after a normal cycle as a sign that the lint screen or exhaust duct is blocked.

1. Unplug the dryer. On a gas dryer, do not strain, kink or disconnect the gas connector. If the dryer cannot be moved without disturbing it, have a qualified person do this job.
2. Pull the dryer out and disconnect the duct. Loosen the clamp at the back of the machine rather than pulling the hose free.
3. Clear the duct with a rotary brush kit. Work from both ends where you can. A drill-driven brush on flexible rods reaches along the run.
4. Clean the exterior vent hood. Check the flap opens and closes freely. Birds’ nests and lint both block it.
5. Vacuum behind and under the dryer. Lint builds up here too. Leave the inside of the cabinet to a qualified service person, as the Consumer Product Safety Commission advises.
6. Reconnect and confirm airflow. Run the dryer for a minute and check outside that the vent cover opens and air is leaving with force.

• Loads still damp at the end of a normal cycle, or taking longer than they used to
• The dryer cabinet or the clothes noticeably hot at the end of a cycle
• A burning smell during operation, which means stop using it now
• Little or no air movement at the exterior vent while the dryer runs
• Lint visible around the vent hood outside

• Cleaning the lint screen and assuming the duct is done: the screen catches only part of it
• Using plastic or foil accordion-type duct, which traps lint and kinks or crushes easily. The Consumer Product Safety Commission says to replace it with rigid or corrugated semi-rigid metal duct
• Crushing the duct against the wall when pushing the dryer back, which undoes the whole job
• Long runs with several elbows that exceed the maximum length in the dryer’s installation instructions

• Large households running daily loads need it more often than once a year
• A long or convoluted duct run traps far more lint than a short straight one
• Pet hair and heavy bedding loads add to the buildup

If the duct runs through a wall cavity, ceiling or roof, or is long with several bends, a professional with proper rotary equipment will clear it rather than push the blockage further along. Gas dryers are also better left to a professional: the US Fire Administration advises having a dryer installed and serviced by one.