Dryer Vent Cleaning: The Fire-Safety Job Most People Skip

Since February our techs have been out on 613 dryer calls. About one in four was some version of the same complaint: the dryer runs, but the clothes come out damp or cold. People run it a second time, then a third, and then they call us.

Plenty of those trace back to air, not heat. A dryer works by pushing hot, wet air out of the house. When the path out is packed with lint, the moisture has nowhere to go, the machine runs hotter and longer, and it gets a little closer to a fire every load.

One thing surprises people when they call. We don't clean dryer vents. We'll clear the lint out of the inside of your dryer and fix what the heat damaged, but the duct running from the back of the machine to the outside of your house is a different job with different tools. So this post covers why that duct matters, how to tell it's clogged, what you can check yourself, and who to call for which half.

Why lint is a fire problem, not just a slow dryer

Lint is a pile of tiny, dry fibers, which makes it close to perfect tinder. Every load leaves a little behind that the screen didn't catch. It settles in the hose, in the bends of the duct, and around the outside flap. As it builds up, airflow drops, the air inside the dryer gets hotter, and now you've got hot air blowing across a layer of kindling.

The U.S. Fire Administration puts it at roughly 2,900 home dryer fires a year, and the leading cause is failure to clean them. Those fires also happen more in fall and winter, when heavier clothes and bedding go through the machine and it runs more often. So September is a good month to deal with it.

Lint our techs pulled out of one dryer. All of it had slipped past the lint screen and packed in where nobody could see it.

What's actually between your dryer and the outside

Most people picture the lint screen and stop there. The screen is just the first of five places lint collects, and the other four are where the trouble starts.

The hose behind the dryer

This is the piece that takes the most abuse. Every time the dryer gets pushed back against the wall, the hose folds a little more. Stacked sets in laundry closets are the worst for this, because nobody pulls them out for years. If you have the white vinyl kind, replace it. Most dryer makers say not to use it at all. The thin foil accordion kind is better but still crushes easily and holds lint in every ridge. Semi-rigid or rigid metal, kept as short and straight as the space allows, is what you want.

Long runs and bends

Every bend slows the air down and gives lint a corner to settle in. The residential building code most of California follows caps a standard dryer duct at 35 feet, and each 90 degree bend counts as 5 of those feet, unless your dryer maker's instructions allow more. A laundry room in the middle of the house, venting up through the attic and out the roof, can use up that budget fast. Those long runs are the ones that clog quietly and are hardest to clean yourself.

The outside hood

Go look at yours. The flap should swing open freely when the dryer runs and close when it stops. We see them stuck shut with lint, painted over, and packed with bird nests. If someone put a screen over the opening to keep critters out, take it off. A screen on a dryer exhaust turns into a lint filter, which is why the code doesn't allow them. A hood with a proper flap or a guard made for dryer vents is the fix.

Signs your vent is clogged

• A normal load takes more than one cycle. Most full loads should dry in 30 to 45 minutes.
• The laundry room gets hot and muggy, or the top of the dryer is hot to the touch.
• Clothes come out much hotter than usual, but still damp.
• You smell something hot or burning while it runs.
• The flap outside barely moves when the dryer is on, or there is lint piling up around it.
• Your dryer shows a vent or airflow warning. A lot of newer models watch airflow and say so.

That last one is more common than people think. Our office notes from this year include dryers flashing blocked vent and duct blockage warnings, and owners who had cleaned the lint screen and couldn't figure out why the message kept coming back. When the screen is clean and the warning won't go away, the duct is the usual suspect.

A ten minute check you can do this weekend

1. Unplug the dryer. On a gas dryer, move it gently so you don't strain the gas line, and don't disconnect it.
2. Pull out the lint screen and clean it. If you use dryer sheets, wash it in warm soapy water and let it dry.
3. Pull the dryer out from the wall and look at the hose. Straighten any kinks. Replace it if it's vinyl, torn, or crushed flat.
4. Disconnect the hose at both ends and clear out any lint you can reach.
5. Go outside, find the hood, and make sure the flap moves freely. Remove any screen and clear any lint or nesting.
6. Reconnect everything, push the dryer back carefully so the hose doesn't fold, and run it on a heat setting.
7. Go back outside. You should feel a strong, steady stream of warm air. If it's weak, the blockage is inside the duct.

If step seven comes up weak, that's the part to hand off. Cleaning a long duct properly takes rotary brushes and a strong vacuum, and on roof vents it takes a ladder and a steady nerve.

Who does what

This is where a lot of people get bounced between companies, so here's the plain version.

For the duct side, we recommend Dryer Vent Wizard of Greater North Bay Area, serving Sonoma, Marin and Napa. Tell them Kelly's Appliance Center sent you. They're in our referral directory.

“We just had the vent cleaned and it still won't dry”

We hear this one a lot, and it makes sense once you know what a clog does on the way to being found. When a dryer can't breathe, it overheats. Most dryers have a thermal fuse, a one-time safety part that blows to cut the heat before things get dangerous. Cleaning the vent doesn't reset it. The fuse has to be replaced, and if the dryer ran hot for months, the heating element or a thermostat may have gone with it.

So if a vent company has been out and the dryer still runs cold, the vent did its job and now the dryer needs one. That's our half. Our post on why a dryer won't heat walks through the usual suspects.

After

Before

How often to do what

• Every load: clean the lint screen.
• Every few months: wash the screen if you use dryer sheets.
• Once a year: have the full duct cleaned. More often with a big household, pets, or a long run.
• When you see signs: have the inside of the dryer cleaned out, especially if you smell burning or find lint on the floor under the drum.

The short version

A clogged dryer vent makes your laundry slow, your power bill higher, and your house a little less safe, and most people never look past the lint screen. Take ten minutes this weekend, check the hose and the outside flap, and feel for that stream of warm air. If the duct needs cleaning, call a vent company. If the dryer still won't dry after that, or it's making noise, or it smells hot, that's where we come in.

We've been fixing dryers in Sonoma, Marin, and Napa counties since 1975. If yours is taking forever and you want someone to tell you which half the problem is on, book a visit or call us at (707) 664-9702.