Dryer Vent Fires and How to Prevent Them

What the fire data shows

The U.S. Fire Administration's topical report on clothes dryer fires in residential buildings, covering 2008 to 2010, is still one of the most detailed public looks at the problem. Its estimates:

• About 2,900 dryer fires in residential buildings were reported to U.S. fire departments each year, causing an estimated 5 deaths, 100 injuries and $35 million in property loss annually.
• Failure to clean was the leading factor contributing to ignition, at 34 percent.
• Dust, fiber and lint were the item first ignited in 28 percent of fires, and clothing in 27 percent.
• Fires were more common in fall and winter, peaking in January at 11 percent.
• 83 percent started in laundry areas.

The figures are more than a decade old, so treat them as a picture of how these fires start rather than a current count. The pattern they show, lint and clothing catching where the dryer sits, is what the prevention advice below targets.

Following one load through the dryer

Walking a single load from the washer to the basket shows where fire can start along the way.

1. LoadingAnything that has soaked up cooking oil, gasoline, paint thinner or alcohol should not go in. The National Fire Protection Association says never to dry items that have come in contact with flammable substances like these. The U.S. Consumer Product Safety Commission adds that clothes soiled with volatile chemicals should be washed more than once and hung to dry if possible.
2. HeatingThe heater warms air, and the drum tumbles the clothes through it. Fibers loosen and ride the air toward the lint screen.
3. The lint screenIt catches most lint, not all. CPSC and USFA both say to clean it before or after every load, and never to run the dryer without it.
4. Inside the cabinetSome lint settles around the drum and inside the machine. NFPA advises removing lint around the drum, and CPSC recommends having a qualified service person clean the inside of the dryer cabinet periodically.
5. The duct and the outside hoodThe rest of the moist, linty air travels through the duct to the outdoors. Every bend, joint and screen along the way is a place for lint to collect and airflow to slow.
6. The finished basketCPSC warns not to leave dried clothes in the dryer or piled in a laundry basket, to prevent them from igniting after drying. Hot laundry piled up holds its heat.

Why airflow is the safety margin

A dryer depends on moving air to carry heat out of the drum. CPSC explains that lint building up in the dryer or exhaust duct can block airflow and cause excess heat, which may start a fire in some dryers. A restricted vent therefore does two things at once: it adds fuel along the path and it keeps more heat in the machine.

That is why the duct material matters. CPSC recommends replacing plastic or foil accordion-type ducting with rigid or corrugated semi-rigid metal duct, since flexible plastic and foil kink, crush and trap lint more easily. NFPA likewise calls for rigid or flexible metal venting to sustain proper airflow and drying time. USFA adds a check most people skip: look at the venting behind the dryer to make sure it is not damaged, crushed or restricted.

Longer drying times, damp clothes after a normal cycle and an outdoor flap that does not open are the usual clues. Our dryer vent cleaning page lists the signs and explains how the full run is cleaned.

Winter makes it worse

USFA's data shows dryer fires peaking in January. Households run more loads of heavy clothing and bedding in cold months, and the outside of the vent faces weather it does not see in summer. NFPA's tip list includes making sure the outdoor vent flap is not covered by snow. After a storm, clearing the hood is as much a part of digging out as clearing the steps.

Holiday visitors and extra laundry also mean more back-to-back loads with less time between cleanings of the lint screen. If a load suddenly takes much longer than usual, stop and check the screen and the outside hood before starting another.

Gas dryers have one more connection

A gas dryer adds a burner and a gas supply to everything above. NFPA advises having gas dryers inspected by a professional to make sure the gas line and connection are intact and free of leaks. The exhaust from a gas dryer also carries combustion products, which is one more reason the vent must run outdoors without leaks or disconnections.

If a gas dryer has to be pulled out to clean behind it, move it gently and do not disturb the gas connection; reconnecting or replacing gas fittings is work for a qualified gas technician. If you notice a gas odor, get out first and call the gas utility or 911 once you are outside. A working carbon monoxide alarm on each level of the home is a sensible backstop in any house with fuel-burning appliances.

Where the vent goes matters

A short, straight run through an outside wall is the easiest kind of dryer vent to keep clear. Longer runs with several elbows, vents that rise through the roof, and ducts hidden in walls, floors or attics collect more lint and are harder to check. The dryer's installation instructions set the maximum length and number of bends for that model, and a run that exceeds them stays a problem no matter how often it is cleaned.

If you do not know where your vent ends, go outside while the dryer runs and look for the hood with air coming out. A vent that ends in the attic, crawl space or garage instead of outdoors is a reason to have the run evaluated, since it drops moist, linty air inside the house.

Setting up the laundry area

Since most dryer fires start in the laundry area, the room around the machine matters as much as the machine.

• Clear space. NFPA says to keep the area around the dryer clear of things that can burn, such as boxes and clothing. CPSC also advises cleaning behind the dryer, where lint builds up.
• Power. NFPA advises using the right plug and outlet, connecting the machine properly and making sure washers and dryers are grounded.
• Space behind the machine. Leave enough room that the transition duct is not crushed when the dryer is pushed back.
• Installation. USFA and NFPA both advise having a dryer installed and serviced by a professional.
• Load size. NFPA says to avoid overloading washers and dryers and to follow the manufacturer's operating instructions.

A routine that covers the risks

• Every load: clean the lint screen; do not leave a running dryer when you go to bed or leave the house, as NFPA advises; take clothes out promptly.
• Every month or so: with the dryer running, step outside and confirm air is leaving the vent and the flap opens, as CPSC and USFA suggest.
• Once a year, or sooner if drying times grow: NFPA's guidance is to clean lint out of the vent pipe or have a dryer lint removal service do it.
• Periodically: have the inside of the dryer cabinet cleaned by a qualified service person, per CPSC.
• Whenever the dryer moves: check that the duct behind it is reconnected and not crushed.

If you see smoke or flames from the dryer, leave, close the door behind you if you can do it on the way out, and call 911.

Questions homeowners ask

Sources

1. U.S. Fire Administration: Clothes Dryer Fires in Residential Buildings (2008-2010), Topical Fire Report Series Vol. 13, Issue 7 (PDF)
2. U.S. Fire Administration: Clothes dryer fire safety flyer (PDF)
3. U.S. CPSC: Overheated clothes dryers can cause fires (Publication 5022, PDF)
4. NFPA: Clothes dryer and washing machine safety tips (PDF, hosted by the U.S. Department of Energy)

This guide is general information. It can't diagnose a specific chimney; an inspection can.