How to Clean a Dryer Vent Duct

Lint is the fuel. A blocked duct is the furnace. U.S. fire departments respond to roughly 14,630 home dryer fires each year, and “failure to clean” accounts for 34% of them. Cleaning the vent duct is a task most homeowners can complete in about 90 minutes, but the right approach depends on your setup: how long the duct runs, what it’s made of, and where it exits the house. This guide walks you through assessing that setup, cleaning the vent, and catching problems along the way.

Scope

Priority	High
Difficulty	DIY
Estimated Time	90 minutes
Frequency	Annual

Tools and Materials

Tools:

• Dryer vent brush kit with flexible rod extensions (12-foot kit for most ducts; 24-foot for longer runs)
• Vacuum with hose attachment
• Screwdriver (for duct clamps)
• Flashlight

Materials:

• Metal duct clamps or foil tape (if current connections are loose)
• 4-inch rigid metal duct sections, if replacement is needed

A basic brush kit costs $20–$40 at hardware stores and lasts for future cleanings.

Before You Handle Anything

Unplug the dryer before disconnecting any ductwork. For a gas dryer, close the shutoff valve on the supply line behind the unit before you pull the dryer away from the wall. Reconnect the gas line carefully afterward and test the connection with soapy water before restarting: bubbles indicate a leak. If you’re not comfortable working around the gas supply valve, have a technician handle the gas connections while you clean the duct, or call a professional for the full job.

The duct exhaust is hot during operation. Let the dryer cool for at least 15 minutes before beginning.

Assess Your Setup First

A standard duct run is a 90-minute DIY job. A complicated one is a different task. Answer these four questions before you pull the dryer away from the wall.

How long is the duct? Measure from the back of the dryer to the exterior termination point. The code maximum is 35 feet, reduced by 2.5 feet for each 45-degree bend and 5 feet for each 90-degree bend. A run longer than 25 feet with multiple bends is harder to clean with a standard brush kit.

What material is it? Rigid metal with a smooth interior and corrugated semi-rigid metal are correct. Flexible plastic or foil accordion duct is not. The ridges in plastic and foil duct trap lint, and both materials are prone to crushing. If yours is plastic or foil, plan to replace it during this cleaning.

Where does it terminate? The duct must exit through an exterior wall or roof cap. A vent that terminates in a crawlspace, attic, or garage deposits lint and moisture where it causes mold and wood decay. If you’re not sure where your duct ends, trace it or check from outside before starting.

Are warning signs already present? Clothes still damp after a normal cycle, longer drying times than usual, or an exterior vent flap that stays closed while the dryer runs all point to a blocked or restricted duct.

Clean, Inspect, Fix: Step by Step

1. Shut off power (and gas). Unplug the dryer. For a gas dryer, close the shutoff valve on the supply line.

2. Disconnect the duct. Slide the dryer forward enough to reach the back. Loosen the clamp or tape connecting the duct to the exhaust port and pull the duct free.

Inspect now: If the duct is flexible plastic or foil accordion material, this is the moment to replace it. Measure the full run, buy 4-inch rigid metal duct sections, and route the new duct with as few bends as possible before proceeding.

3. Vacuum the exhaust port and duct end. Use the vacuum hose to clear the opening at the back of the dryer and the first section of duct. Remove visible lint by hand first.

4. Run the brush kit from the interior. Feed the brush into the duct from the dryer end, adding rod extensions as you go. Push in short strokes and rotate the brush to break up packed lint. Work toward the exterior termination.

Inspect now: If the brush stops and won’t advance, you’ve hit a kink, crushed section, or tight bend. Back the brush out, note the distance, and check the duct at that point. A crushed or kinked section needs to be cut out and replaced, not forced through.

5. Clean from the exterior. Go outside and remove the vent cover. Clear lint from the cover and opening by hand or with the brush. Feed the brush kit in from the exterior to dislodge anything the first pass left behind. Vacuum the opening.

Inspect now: The vent flap or louver should open freely and close under its own weight. A stuck, corroded, or nest-blocked cover restricts airflow as much as a lint clog. Clean or replace it before continuing.

6. Vacuum behind and under the dryer. Lint accumulates outside the duct. Vacuum under and behind the unit before sliding it back into place.

7. Reconnect and secure. Reattach the duct to the exhaust port with a metal clamp or foil tape. Confirm the connection is snug and the duct doesn’t kink between the dryer and the wall. Slide the dryer back with a few inches of clearance so the duct curves rather than folds.

For gas dryers: reopen the supply valve and test the connection with soapy water. Do not proceed if bubbles appear.

8. Run a test cycle. Plug the dryer in and run it on air-dry or fluff for 15–20 minutes. Check outside to confirm the vent flap opens and exhaust air flows freely.

Confirming the Job Is Done

The vent flap opens fully while the dryer runs. Exhaust air flows strongly from the exterior opening. A test load dries in its normal cycle time. There are no burning smells during operation.

If drying times remain long after cleaning, the duct may have an inaccessible section, a disconnected joint inside a wall, or an undersized termination cap. These require professional inspection.

Mistakes That Undo the Work

Leaving flexible foil or plastic duct in place. Cleaning an accordion duct removes surface lint but doesn’t fix the underlying restriction. The ridges continue to trap lint and reduce airflow.

Using duct tape on connections. Standard duct tape dries out and fails. Use a metal clamp or foil tape.

Cleaning only from the inside. Working from one direction leaves a lint plug near the termination end. Always clean from both the interior and exterior openings.

Compressing the duct when pushing the dryer back. A tight kink near the wall restricts airflow as much as lint buildup. Confirm the duct curves gently, with a few inches of clearance from the wall.

When Something Still Isn’t Right

Problem	Likely Cause	What to Try
Drying times still long after cleaning	Inaccessible lint blockage or disconnected joint inside a wall	Call a professional with commercial rotary brush equipment
Brush kit won’t pass through a section	Crushed duct, kink, or severe bend	Locate and replace the damaged section
Exterior vent flap doesn’t open	Debris or nest blocking the cover	Remove the cover and clear the opening; replace the cover if damaged
Burning smell during test cycle	Lint inside the dryer chassis	Have the dryer interior professionally serviced
Soapy water bubbles at gas connection	Leaking fitting	Do not use the dryer; call a technician

When to Call a Professional

• The duct runs longer than 25 feet or has more than two 90-degree bends
• The duct passes through walls or ceilings where sections can’t be inspected or replaced
• The duct terminates in a crawlspace, attic, or garage (requires correction before the dryer is used)
• You find a disconnected joint inside a wall
• You have a gas dryer and aren’t comfortable working around the supply valve
• The brush kit can’t pass through a section you can’t access for replacement

Keeping the Duct Clear

Clean the lint screen before or after every load. If you use dryer sheets, scrub the screen with a brush and water monthly: the residue they leave reduces airflow even when the screen looks clean.

Clean the full duct once a year for typical use (four to seven loads per week). If you dry frequently or wash heavy-shedding items like pet bedding and towels, clean it every six months. Lint buildup reduces dryer efficiency by over 30%, which shows up on your utility bill before you’d notice longer drying times.

Each spring, spend two minutes checking the exterior vent cover for debris, bird nests, or corrosion. A clear termination point is the simplest part of the system to maintain, and the easiest to overlook.