Last fall a load of towels in my apartment took three full cycles to dry, and I blamed the towels. Then the laundry room started feeling like a sauna, and the outside flap on the vent barely moved when the dryer ran. When I finally pulled the dryer out, the foil duct behind it had a lump of lint the size of a dinner roll. That was the moment I looked up how often to clean a dryer vent and realized I’d been doing it never, which is apparently very normal and also how a lot of house fires start. My answer now is once a year, and September is the month I’d pick, before the heavy-sweater, wet-boots, flannel-sheets season sends your dryer into overtime.
Dryer fires peak in the months right after this one
The U.S. Fire Administration, part of FEMA, estimates about 2,900 clothes dryer fires in homes each year, causing around 5 deaths, 100 injuries, and $35 million in property loss. The leading factor, involved in 34% of those fires, is plain failure to clean. In a third of these fires, the problem was lint someone could have removed in an hour.
The timing matters too. USFA’s report found dryer fires are more common in fall and winter, with January the single worst month at 11% of incidents. That makes sense when you think about what’s in the drum in January: heavier fabrics, more loads, and dryers running longer to deal with them. If you clean the vent in September, you go into the risky months with a clear line instead of a year’s worth of buildup.
The lint screen catches less than you think
Most of us empty the lint trap and figure we’re done. The screen catches a lot, but plenty of fine lint slips past it and settles along the duct, especially at bends and anywhere the duct sags. Over months, that layer narrows the path the hot, wet air takes out of your house. The dryer then runs hotter and longer, and the lint sitting closest to the heat is the fuel in every one of those USFA fire numbers.
The National Fire Protection Association says the classic warning sign is clothes taking longer than usual to dry, which usually means the vent pipe is clogged. USFA’s dryer safety flyer adds a check you can do in ten seconds: go outside while the dryer runs and make sure the vent cover opens. Those were the two signs I ignored for months. If you have either one, don’t wait for September.
One more thing worth checking while the dryer is pulled out: the duct itself. NFPA recommends rigid or flexible metal venting, and USFA says to check that the duct behind the dryer isn’t crushed or restricted. Thin foil accordion duct is the kind that crushes and sags most easily. Mine was the crinkly foil kind, and it had a kink right behind the machine.
What a clogged vent costs you before it’s ever dangerous
Here’s the part I didn’t expect. A clogged vent costs you money every week, long before it becomes a fire risk, and you can estimate how much.
A typical electric dryer draws somewhere around 5,000 watts while it’s heating. Call it 5 kilowatt-hours for each hour of running, which at 18 cents a kilowatt-hour (look at your own bill for your rate) is about 90 cents an hour. Say a clean vent dries a load in 45 minutes, and the clog has stretched that to 75 minutes. That’s an extra half hour per load, or about 45 cents.
At five loads a week, the extra time adds up to 2.5 hours, which is $2.25 a week. Over 52 weeks, that’s about $117 a year spent heating air that can’t get out. A professional dryer vent cleaning runs about $143 on average according to HomeAdvisor, with most people paying between $103 and $184. In this example, the cleaning pays for itself in a little over a year, and that’s before you count the towels that stop smelling musty.
Your numbers will vary with your dryer, your rates, and how bad the clog is. But if your loads have quietly gotten longer, you’re paying for it either way, either on the power bill or to the vent cleaner.
How often to clean a dryer vent yourself, and how to do it in an hour
If your vent run is short and straight, you can handle it. A dryer vent brush kit with flexible rods that screw together costs about $20 to $30 at a hardware store. Unplug the dryer (and turn off the gas if it’s a gas dryer, then don’t touch the gas line), slide it out, and disconnect the duct from the back. Run the brush through the duct and through the wall opening, working toward the outside, and vacuum what comes out. Then go outside and clear the vent hood and the flap. Reconnect, push the dryer back without crushing the duct, and run an empty cycle on air-only to blow out what’s left.
Call a pro if your vent runs a long way, goes up through a roof, has several bends, or if you live in a building where the ducts are shared. Long runs are exactly where lint piles up, and a brush won’t reach the middle.
Put it on the fall list with the smoke alarms
I keep a short fall list taped inside a kitchen cabinet, a much smaller cousin of the spring cleaning checklist I do in March. Dryer vent, smoke and carbon monoxide alarm batteries, the furnace filter, and the gutters. It takes one weekend, and I don’t think about any of it again until next year.
So, how often to clean your dryer vent? NFPA’s answer is at least once a year, and sooner if drying slows down. I’d go more often if you have a big household, pets that shed, or a long duct run, and right away if your loads are taking longer than they used to. Clean the lint screen every single load, which takes five seconds; USFA says before and after each cycle. And never leave a dryer running when you’re leaving the house or going to bed, an NFPA tip I follow now without exception. The lump of lint I pulled out of my duct last year lives in my memory as the scariest thing in my apartment, and it cost me nothing but an hour to get rid of.