Clogged dryer vent: the signs and how to check

Updated September 23, 2026 · Every figure checked twice against its source · How we verify

The clearest sign of a clogged dryer vent is a load that takes longer than it used to: the USFA says that when jeans or towels take a long time to dry, or clothes feel hotter than usual at the end of a cycle, a clogged vent is the likely problem. Check the outside flap while the dryer runs. If it does not open, air is not getting out.

Signs of a clogged dryer vent

Sign	What it tells you	Source
Heavy loads such as jeans or towels take a long time to dry	Moist air is not leaving fast enough	USFA
Clothes feel hotter than usual at the end of the cycle	Hot air is not leaving with the exhaust	USFA
The outside flap does not open while the dryer runs	The run is blocked or the hood is stuck	NFPA tip sheet
An "AF" or airflow code on the control panel	On Whirlpool models with airflow detection, a blocked or partly blocked vent, or a run that is too long	Whirlpool
A crushed or kinked hose behind the dryer	Restricted airflow before the air even reaches the wall	USFA; Whirlpool
Nesting material at the outside vent	A blockage at the exit	USFA

What happens when dryer vent is blocked?

The dryer keeps heating but cannot push the air out. The USFA explains that reduced airflow from lint buildup can make a dryer run inefficiently and possibly overheat, and that lint is highly combustible. That combination is why failure to clean was the leading factor in residential dryer fires in USFA data (34 percent, 2008 to 2010) and in NFPA's newer estimate (32 percent, 2014 to 2018). A blocked vent also costs you in time: every load runs longer.

A blocked vent can also mean the exhaust is going somewhere it should not. The USFA warns that faulty installations can vent exhaust into the attic, crawl space, chimney or interior walls, causing poor indoor air and mold.

How to check if dryer vent is clogged

Whirlpool's venting specification lists these checks for an airflow warning. They work for any vented dryer:

Look at the run from the dryer to the wall. Pull the dryer out and check the hose is not crushed or kinked.
Check that section for lint and debris. Disconnect it and look inside.
Check the outside hood. Clear lint and debris, then confirm the flap opens while the dryer runs.
Check the length. Confirm the run and the number of elbows fall within your dryer's limit. The code limit is 35 feet with deductions for each elbow; see dryer vent repair and the code rules.
Test again. Whirlpool says to run a timed heated cycle; if the warning persists, have the entire vent run cleaned.

On a gas dryer, be careful moving the machine. The NFPA and the USFA both say the gas line and connection should be checked by a qualified professional.

How to clean a clogged dryer vent

A light lint buildup in a short, reachable run is a DIY job with a brush kit; our step-by-step guide covers how to clean a dryer vent. Call a professional dryer vent cleaning service for a roof vent, a run longer than your brush, a nest, or a crushed duct inside a wall. Cleaning a clogged vent costs $100 to $200, according to Fixr; see the full dryer vent cleaning cost guide.

Dryer not drying after cleaning vent

If the vent is clean and loads are still slow, work back through the checklist above. The Whirlpool steps point to three causes a cleaning does not fix: a crushed transition hose, a run that is too long or has too many elbows for the dryer, and a hood or flap that stays shut. A run that is too long needs a reroute, not another cleaning. If none of those apply, the problem may be in the dryer itself, which is a job for an appliance technician.

Clogged dryer vent: common questions

How to tell if your dryer vent is clogged

Watch drying time and heat. The USFA says long drying times for heavy items such as jeans or towels, or clothes that feel hotter than usual at the end of the cycle, point to a clogged vent. Then check that the outside flap opens while the dryer runs.

What are signs a dryer vent needs cleaning?

Slow drying, hot clothes, a flap that does not open, lint or nesting material at the outside hood, and an airflow code on dryers that have one. Even without signs, the NFPA says to clean the vent pipe once a year.

Clogged roof dryer vent

Roof vents clog more than wall vents, according to Fixr, because they are more exposed to the elements. Cleaning one costs $150 to $250 (HomeGuide) or $150 to $300 (Fixr). Roof work carries a fall risk, so this one is worth hiring out.

Dryer vent clogged with lint

Lint gets past the lint screen: the USFA says lint is carried through the vent system along with the moist air. Clean the full run with a brush and vacuum, clean the lint screen every load, and clean the vent once a year per the NFPA.

Blocked dryer vent

A blocked vent can be lint, a nest, a crushed hose or a stuck flap. Fixr prices clearing a clog at $100 to $200 and removing a bird nest at $150 to $400.

Sources

U.S. Fire Administration, "Clothes Dryer Fires in Residential Buildings (2008 to 2010)", August 2012: usfa.fema.gov
NFPA, "Clothes dryer safety" tip sheet: nfpa.org
NFPA, "Home Dryer Fires", Marty Ahrens, June 2020: content.nfpa.org
Whirlpool, "Dryer venting specifications" (W11688180A): whirlpool.com
International Code Council, 2021 International Residential Code, section M1502: codes.iccsafe.org
Fixr, "Dryer vent cleaning cost", updated January 31, 2025: fixr.com
HomeGuide, "How much does dryer vent cleaning cost?", page dated April 29, 2024: homeguide.com

All sources read September 23, 2026.