TL;DR
Clean the dryer exhaust duct at least once a year -- more often with a long run, a household that dries daily, or pets in the house. Failure to clean is the leading contributing factor in home clothes dryer fires, and the duct, not the lint screen, is where the dangerous accumulation happens. Source: National Fire Protection Association
The duct matters more than the screen
The lint screen catches most fiber, but not all of it. What gets past settles in the blower housing and then in the exhaust duct -- on every bend, in every sag, and especially at the outside vent flap where airflow slows and moisture condenses.
That lint is dry, fine and highly combustible, sitting in a hot air path. Which is why a household can clean the lint screen after every load, exactly as recommended, and still have a genuine hazard behind the wall. Clean the lint trap after every load, and clean the duct annually. Both, not either.
How do you clean a dryer vent duct?
Unplug the dryer, pull it away from the wall, disconnect the duct from the machine, and vacuum out the blower outlet. Then run a flexible lint brush through the duct from both the inside end and the outside vent, vacuuming as you go. Reconnect, tape the joints, and run a test cycle.
What you need
- A vacuum with a hose and a crevice tool. A shop vacuum is better than a household one.
- A flexible dryer vent brush kit, the kind with screw-together fiberglass rods. Manual is fine.
- Foil duct tape. Not fabric duct tape, which fails in heat.
- A screwdriver and possibly a nut driver for the duct clamp.
- A flashlight, gloves and a dust mask.
Step by step
1. Cut the power, and the gas. Unplug an electric dryer. For a gas dryer, shut the gas supply valve behind the machine as well. If you are not confident disconnecting and reconnecting a gas dryer, have the gas line handled by a qualified technician and do only the outside-vent portion yourself.
2. Pull the dryer forward. You need eighteen inches or so. Walk it out gently rather than dragging, and watch the gas line if there is one.
3. Disconnect the duct. Loosen the clamp where the duct meets the dryer outlet and slide the duct off. Expect a lint cloud.
4. Vacuum the dryer outlet. Get the crevice tool into the blower outlet on the back of the machine and clear everything you can reach. This is often where the heaviest packing is.
5. Brush the duct from the inside end. Feed the brush in, add rods as you go, and work it back and forth. Pull it out slowly, dragging lint with it, and vacuum what comes out.
6. Go outside and do the other end. Open or remove the exterior vent hood cover and clear the lint packed around the flap -- usually the worst single spot, because it is where warm moist air meets cold. Brush inward from there and vacuum. Confirm the flap moves freely, and remove any wire mesh or screen: those are lint traps, not pest control.
7. Reconnect properly. Slide the duct on, tighten the clamp, and seal the joints with foil tape. Never use screws through duct joints -- protruding points catch lint and build a blockage.
8. Push the dryer back without crushing the duct, then restore power and gas, run a heated cycle, and check for strong warm airflow at the outside vent hood.
Rigid metal, semi-rigid, or foil? It matters
Flexible plastic and thin foil accordion ducting is not appropriate for a dryer exhaust. The ridges catch lint, the material sags and traps moisture, and it is far more likely to be crushed behind the machine.
Rigid metal duct is the right material for the concealed run, with a short semi-rigid metal transition from the machine to the wall. If your dryer is connected with white vinyl or thin foil accordion hose, replacing it is the single highest-value change you can make. Keep the run short and minimize elbows, since each elbow adds resistance equivalent to several feet of straight duct.
How often, and when to call someone
Once a year is the baseline. Go to every six months if the household dries several loads a day, if the duct run is long or has multiple turns, or if you have shedding pets.
Call a professional duct cleaning service if the run goes through an attic or an upper floor, if you cannot locate the exterior termination, or if the dryer is gas and you are not comfortable with the connection. Evidence of a rodent or bird nest belongs to a pest control specialist, not a cleaning routine.
Warning signs you should not wait on
- Loads that need two cycles. Start with why clothes take two cycles to dry.
- A burning or hot-lint smell during a cycle. Stop the dryer and investigate.
- Clothes that are very hot at the end of the cycle.
- The room getting humid or the machine cabinet getting hot to the touch.
- The outside vent flap barely moving while the dryer runs.
One absolute rule: never put anything contaminated with gasoline, paint thinner, or any flammable solvent into a clothes dryer, no matter how many times it has been washed. Vapors plus heat plus an ignition source is how dryer fires and explosions happen. Gasoline on clothing covers what to do instead.
FAQ
How often should a dryer vent be cleaned?
At least once a year for a typical household. Every six months if you dry multiple loads daily, have a long or twisting duct run, or live with shedding pets. Any time drying takes noticeably longer than it used to, clean it regardless of the calendar.
Can I clean a dryer vent myself?
Usually yes, if the run is short and reaches an exterior wall on the ground floor. A vent brush kit and a vacuum handle it in about an hour. Long runs through attics or upper floors, and gas dryers you are not comfortable disconnecting, are better handled by a professional.
What are the signs of a clogged dryer vent?
Longer drying times, very hot clothes or a hot cabinet, a humid or musty laundry room, lint appearing around the door seal, and weak or no airflow at the exterior vent hood while the dryer runs. A burning smell means stop the machine immediately.
Is flexible foil dryer duct safe?
Thin foil accordion and plastic ducting are poor choices because the ridges trap lint, the material sags and crushes easily, and it holds moisture. Rigid metal duct for the concealed run with a short semi-rigid metal transition is the appropriate setup.
Should I put a screen on the outside dryer vent?
No. Screens and wire mesh over a dryer vent hood clog with lint quickly and cause exactly the blockage you are trying to prevent. Use a proper vent hood with a working flapper instead, and check it during your annual cleaning.
Does a ventless or condenser dryer need duct cleaning?
There is no duct to clean, but ventless and heat pump dryers have their own filters and a condenser or evaporator coil that must be cleaned on the manufacturer schedule. A clogged condenser produces the same symptom -- loads that will not dry -- for a different reason.
Where this is one task among many, recurring house cleaning services take the broader load.
While you are back there, the space behind and under the machines usually needs attention too. A laundry room cleanout is a good pairing, and so is a check for residue inside the dryer drum. If the room is part of a bigger list, every home is different, so the real number depends on size, condition, and what you want covered. Get a quote and we will walk you through it.