Signs Your Dryer Vent Is Clogged (and What to Do)

If your dryer needs two cycles to finish a load, the vent is the first thing to rule in or out. It is not the only cause, and the sources below are careful to say so. This guide lists the signs, the check you can do in a minute at the outside wall, what to do with the result, and the other things that make a dryer slow. Our dryer vent cleaning page covers the service.

The signs, in the sources’ own words

Note the wording. The CPSC says “may be a sign” and lists the lint screen along with the duct. Samsung says “probably.” GE describes the same cluster, a dryer that is hot to the touch, sweats and takes longer to dry, and says a partly clogged exhaust “can impair performance.” Whirlpool adds that visible damage to the duct is a sign the duct itself needs replacing.

The outside flap check

The CPSC gives this test: “Check the outside dryer vent while the dryer is operating to make sure exhaust air is escaping. If it is not, the vent or the exhaust duct may be blocked.” The U.S. Fire Administration words it as making sure “the outdoor vent covering opens when the dryer is operating.”

1. Start the dryer on a heated cycle with a load in it.
2. Go outside to the vent cap on the wall. Find it from inside by following the duct, or from outside by looking for the small hood or louvered cover.
3. Hold your hand near the opening. You should feel warm, moist air, and the flap should be pushed open.
4. Look at the cap itself. GE says snow or ice should not be allowed to build up around it, and the U.S. Fire Administration says to check that nests of small animals and insects are not blocking it. An energy.gov-hosted article adds that birds or rodents sometimes block dryer vents.

Little or no air with the dryer running points to a blockage somewhere between the drum and the cap. A strong flow does not clear the rest of the system, but it makes a full-length clog less likely.

Rockford’s January average is 21.8 degrees F (National Weather Service, Rockford normals 1991-2020, 1991 to 2020), so the outside cap is worth a look after snow. Nicor Gas, in its customer safety insert, says snow or ice covering the outside venting of a furnace, water heater or clothes dryer “can cause hazardous buildup of carbon monoxide.” It asks you to clear snow with your hands or a broom, not a shovel or mechanical equipment.

Samsung’s vent blockage test and Whirlpool’s Check Vent light

Some dryers will tell you. Samsung describes a blockage test on certain models: “A code like C8 or C80 indicates about 80% clogged, and a code like C90 or C9 indicates about 90% clogged.” It is model specific, so look in your manual before you rely on it (Samsung, Run a Vent Blockage test on your Samsung dryer).

Whirlpool’s Check Vent light page tells you to check that the vent hood on the outside is not clogged or blocked by landscaping, then to clean the venting inside the house, which “may require a Vent Cleaning service person, depending on the venting.” The page says the venting needs cleaning every one to two years, or as needed when drying performance drops.

What to do next

1. Clean the lint screen and rerun a load. The CPSC says to do this before or after every load.
2. Do the flap check above.
3. Look at the duct behind the dryer if you can pull it out safely. The CPSC says the duct should not be crushed or kinked, and says to replace foil or plastic accordion duct with rigid or corrugated semi-rigid metal.
4. Clear the blockage or hire it out. The CPSC says it may be necessary to disconnect the duct from the dryer and to “reconnect the ducting to the dryer and outside vent before using the dryer again.” Pros and cons of doing this yourself are in can you clean a dryer vent yourself.

If you hire it, the price is a national figure, since no guide publishes one for Rockford. Angi lists $104 to $188 (updated October 14, 2026) and Thumbtack $186 to $510. The cost page has the sources and the extra charges for a nest or a damaged duct.

When it is not the vent

• The lint screen. A screen that is full, or coated in a film, cuts airflow before the air reaches the vent. The CPSC lists the screen in the same sentence as the duct.
• The inside of the dryer. The CPSC says to clean behind the dryer and to “have a qualified service person clean the interior of the dryer chassis periodically.” A clean vent does not clean the cabinet.
• A crushed transfer hose. Samsung lists a crushed hose among other causes of damp loads. So do the CPSC’s remarks on kinks and crushing.
• Dryer sheet residue on the sensor bars. Samsung lists this as another cause on its not-drying page.
• A cold laundry area. GE says the dryer should be used in a heated location, because in an unheated one “particularly in the cooler months” it can sweat.

GE also notes that venting problems are not considered a manufacturing defect and are not covered by the warranty. Knowing the cause before you call a repair service can save a visit.

Gas dryers: when to stop

A gas dryer exhausts combustion gases as well as moisture. The International Residential Code says a gas dryer’s exhaust must “convey the moisture and any products of combustion to the outside of the building.” GE warns: “Do not operate a gas dryer without the vent; possible carbon monoxide fumes could enter the room around the dryer.” That is why the disconnect-and-test step that appears in some electric-dryer troubleshooting is not for a gas model.

The Illinois Office of the State Fire Marshal lists dryers among the appliances that can produce carbon monoxide when faulty or poorly repaired. If you smell gas or a carbon monoxide alarm sounds, stop using the dryer and have the appliance and its vent checked before you run it again. Illinois law requires an alarm near sleeping rooms: Every dwelling unit needs at least one working carbon monoxide alarm within 15 feet of every room used for sleeping, required since January 1, 2007. The State Fire Marshal says the law applies to homes that burn fossil fuel (natural gas included) to cook, heat or make hot water, or that have an attached garage. A wood fireplace alone is not named. See the Illinois carbon monoxide alarm law.

NFPA found that gas dryers appear in fires at about the rate they are used. Of the dryers in home fires in its 2014 to 2018 data, 78 percent were electric and 22 percent were gas, which NFPA calls generally consistent with usage. Gas dryers are not riskier for fire on those numbers. The carbon monoxide point is a separate question.