How to Fix and Clean a Dryer Duct: Preventing Fires and Improving Efficiency

A clogged dryer duct is one of the most common — and most overlooked — fire hazards in a home. Lint is extremely flammable, and every load of laundry deposits more of it inside the duct.

A clogged dryer duct is one of the most common — and most overlooked — fire hazards in a home. Lint is extremely flammable, and every load of laundry deposits more of it inside the duct. Most homeowners never clean the duct beyond the lint trap, which catches only about 75 percent of the lint the dryer produces.

This guide covers how to diagnose a blocked duct, clean it from end to end, and replace accordion flex duct with rigid metal for a permanent fix.

What You Need

• Dryer vent brush kit — flexible rods with a lint brush that reaches the full duct length
• 4-inch foil rigid duct — smooth interior, code-compliant for in-wall runs
• Flexible dryer vent cleaning rods — attach to a drill for powered scrubbing
• HVAC foil tape — heat-rated tape for sealing duct joints
• Dryer vent booster fan — extends allowable duct length for longer runs
• Dryer vent clog alarm — alerts when airflow drops below safe levels

Why Dryer Vents Fail

Two problems account for the majority of dryer duct failures: lint accumulation and flexible duct kinking.

Lint accumulation happens gradually. Every load deposits a thin layer of lint on the duct walls. Over months and years, this builds into a thick crust that restricts airflow and can ignite. The lint trap catches most but not all lint — fine fibers pass through and coat the duct interior. Longer ducts with more bends accumulate lint faster because turbulent airflow at the elbows deposits lint at those transition points.

Flexible duct kinking is a problem specific to accordion-style flex duct. When a dryer is pushed too close to the wall, the flex duct behind it collapses into an S-shape or kink. This restriction doubles or triples the effective duct length and can completely block airflow even if the duct is otherwise clean. Kinked flex duct also traps lint at the kink point, where it cannot be brushed out without disconnecting and straightening the duct.

Signs of Blockage

Check for these warning signs before doing any cleaning:

• Clothes are still damp after a full cycle, or require two cycles to dry completely.
• The laundry room feels hot or humid when the dryer is running.
• The dryer exterior is hot to the touch.
• You smell something burning — even faintly — during a cycle.
• The exterior vent flap stays closed or barely opens when the dryer runs.
• Lint or moisture appears around the connection between the dryer and the wall duct.

Any one of these signs justifies immediate cleaning. Multiple signs together indicate a serious blockage.

Step-by-Step Duct Cleaning

1. Unplug the dryer or shut off the gas valve if it is a gas dryer.
2. Pull the dryer away from the wall at least 2 feet to access the duct connection.
3. Disconnect the flex duct from the back of the dryer and from the wall fitting. This connection is typically held by a hose clamp or a slip fit.
4. Clean the wall duct from the inside. Feed the brush kit rods into the wall duct, connecting extensions as you go, and rotate the brush to dislodge lint. Have a helper check the exterior vent for lint being pushed out.
5. Clean from the exterior end. Remove the exterior vent cap and brush from that end toward the interior. This dislodges lint that the interior pass did not reach.
6. Vacuum the connection at the wall and the transition area behind the dryer.
7. Inspect the flex duct for kinks, tears, or crushed sections. Replace it if damaged.
8. Reconnect the duct and seal any joints with HVAC foil tape.
9. Push the dryer back — leave at least 4 inches of clearance at the rear so the flex duct does not kink.
10. Run a test cycle with a damp towel and check that the exterior vent flap opens fully within 30 seconds.

Replacing Flex Duct with Rigid Metal Duct

If the duct run is accessible in a laundry room or utility space, replacing accordion flex duct with rigid metal is the best permanent fix. Rigid duct does not accumulate lint at the same rate, cannot kink, and is the only type permitted in enclosed spaces.

Steps:

1. Measure the existing duct run from the dryer outlet to the exterior vent, including any turns. Rigid duct comes in 4-foot sections.
2. Calculate equivalent length: straight sections count as actual length, each 90-degree elbow counts as 5 feet, each 45-degree elbow counts as 2.5 feet. Total must be under 25 feet for most installations.
3. Cut rigid duct to length with metal snips where needed.
4. Connect sections with the male end (crimped end) going in the direction of airflow — toward the exterior.
5. Seal all joints with HVAC foil tape on the outside of the connection.
6. Connect the final section to the exterior vent and seal that joint.
7. Leave a short section of UL-listed foil flex duct — maximum 8 feet — as the transition between the dryer (which moves for maintenance) and the fixed rigid duct. Secure both ends with hose clamps.

Related Reading

• How to Clean a Dryer Vent
• How to Fix a Dryer Not Heating
• How to Fix a Noisy Dryer
• Annual Home Maintenance Schedule