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How to clean a dryer vent, and how often?

By Roof & Router Team. Updated October 11, 2026.

How common are dryer fires?

The NFPA estimates U.S. fire departments responded to about 15,970 home fires per year involving clothes dryers or washing machines (2010-2014 annual average). Dryers were involved in 92% of them.

The derived counts are simple arithmetic: 15,970 × 0.92 ≈ 14,690, and 15,970 × 0.31 ≈ 4,950. The NFPA fact sheet covers dryers and washers combined, so treat these as approximate.

Lint is the problem. CPSC warns: “Fires can occur when lint builds up in the dryer or in the exhaust duct.”

How often should you clean a dryer vent?

Clean more often if you run several loads a day, dry lots of towels or bedding, or have a long duct run. Never run the dryer without the lint filter in place.

What are the signs a dryer vent is clogged?

CPSC lists two clear warning signs. Clothes are still damp at the end of a normal cycle, or drying takes longer than it used to. Other things to check:

• The outdoor flap does not open, or opens only slightly, while the dryer runs.
• You feel little or no air at the outside hood.
• Lint collects around the outdoor opening or behind the dryer.
• The duct is crushed or kinked behind the machine.

If you notice a burning smell, stop the dryer and do not use it until the vent is checked.

How do you clean a dryer vent yourself?

You need a dryer vent brush kit (flexible rods with a round brush), a vacuum with a hose attachment, a screwdriver or nut driver, and clamps or UL 181 foil tape (not cloth duct tape).

1. Unplug the dryer. For a gas dryer, also close the gas shutoff valve.
2. Pull the dryer out gently. Leave room to work without stretching the gas line or power cord.
3. Detach the transition duct. Loosen the clamp at the dryer outlet and at the wall.
4. Vacuum the dryer outlet and the wall opening. Clean the lint screen slot too.
5. Brush the duct. Feed the brush in from inside. Rotate it in the direction the kit specifies so the rods do not unscrew. Pull lint out as you go.
6. Brush from outside. Remove the hood cover if possible and brush back toward the house. Don’t brush roof or second-story vents from a ladder; hire a pro.
7. Clean the outdoor hood. Remove lint, nests, or debris. Confirm the flap moves freely.
8. Reconnect the duct. Use clamps or UL 181 foil tape, not cloth duct tape. Do not use screws that stick into the duct, since they catch lint.
9. Test it. Run the dryer on air or low heat. Go outside and confirm air is escaping and the flap opens.

What type of dryer duct should you use?

CPSC says to replace plastic or foil accordion-type duct with rigid or corrugated semi-rigid metal duct. Its reason: flexible plastic or foil duct traps lint more easily and is more likely to kink or crush. San Diego Fire-Rescue also calls for rigid or flexible metal venting to keep proper airflow and drying time.

The model residential code (IRC M1502.4.1) requires exhaust ducts made of metal at least 0.0157 inch thick (No. 28 gage).

How long can a dryer vent be?

Under IRC Section M1502.4.5, the maximum exhaust duct length is 35 feet. Fittings reduce that limit. For standard mitered elbows, subtract 5 ft per 90° and 2.5 ft per 45°. Smooth, larger-radius elbows subtract less (see IRC Table M1502.4.5.1), and the manufacturer’s installation instructions take precedence. Local codes vary.

Formula (mitered elbows): allowed length = 35 ft − (5 ft × number of 90° elbows) − (2.5 ft × number of 45° elbows)

The code also limits the flexible transition duct behind the dryer to 8 feet. It requires a backdraft damper at the outside termination and prohibits screens there, because screens collect lint.

What should you check on the outdoor vent flap?

San Diego Fire-Rescue and CPSC both say to check that the outdoor flap opens when the dryer runs. A stuck flap blocks airflow. A flap that never closes lets in cold air, rain, and pests. Check it each season, and add it to your winterize house checklist. Do not add a screen or cage that traps lint.

Is cleaning a gas dryer vent different?

Yes. A gas dryer burns fuel, so the vent also carries combustion gases outside. A blocked vent can push those gases, including carbon monoxide, back into the house. Keep a working CO alarm on each level of the home.

When moving a gas dryer:

• Close the gas valve first.
• Do not kink, twist, or crush the flexible gas connector.
• After reconnecting, have the gas line checked. San Diego Fire-Rescue says gas dryers should be inspected by a professional to make sure the gas line and connection are intact.
• If you smell gas, leave the house and call the gas utility from outside.

When should you hire a professional?

Hire a dryer vent cleaning service or HVAC contractor if:

• The duct runs more than a few feet through walls, a ceiling, or an attic.
• The vent exits through the roof or a second-story wall. Don’t brush these from a ladder.
• Brushing does not fix long drying times.
• The duct is crushed, disconnected inside a wall, or made of plastic or foil inside a wall.
• You have a gas dryer and are not comfortable with the gas connection.

Quick answers

How often should I clean my dryer vent? At least once a year for the vent duct, and every load for the lint screen. Clean the duct sooner if drying times increase.

Can a clogged dryer vent cause a fire? Yes. Failure to clean is the leading cause of home dryer and washer fires, at 31% in NFPA data.

Is foil dryer duct safe? CPSC recommends replacing foil or plastic accordion duct with rigid or semi-rigid metal duct. Foil traps lint and crushes easily.

What is the maximum length for a dryer vent? The IRC allows 35 feet, minus 5 feet per 90-degree and 2.5 feet per 45-degree standard mitered elbow. Smooth, larger-radius elbows subtract less, and the manufacturer’s instructions take precedence.

Can a gas dryer vent leak carbon monoxide? A blocked vent can send combustion gases indoors. Keep the vent clear and install CO alarms.