The flap or louvers on an exterior dryer vent should move when the dryer is pushing air outside. CPSC specifically recommends checking that the outdoor vent flap opens while the dryer operates because restricted exhaust can trap heat and lint in the system. If the flap stays shut, do not solve the symptom by propping it permanently open. First determine whether air is reaching the hood at all.
QUICK STEPS
If you need the short version, try these steps first.
- Clean the lint screen and confirm the dryer is not overloaded.
- Observe the exterior flap during a short dryer run from a safe position.
- Turn the dryer off and remove visible lint or debris from the exterior hood without pushing it into the duct.
Before you continue, check these safety points.
- Do not keep running a dryer with little or no exhaust airflow; restricted ducts can overheat and contribute to a lint fire.
- Do not climb onto a roof or use an unsafe ladder position to inspect a high vent termination.
- Do not pull a gas dryer far enough to stress or disconnect the gas connector; use qualified service if the appliance must be moved significantly.
Confirm the flap is actually failing while the dryer is exhausting
Run the dryer on an air or timed cycle only long enough to observe the exterior hood from a safe location. The flap or louvers should move and warm exhaust air should be noticeable. CPSC advises homeowners to make sure the exhaust vent pipe is not restricted and the outdoor flap opens when the dryer is operating.
If the hood is on a roof, high wall, or other location that requires an unsafe ladder position, do not climb up just to watch it. Observe from the ground if possible and use a qualified vent-cleaning or service professional for inaccessible terminations.
Start at the lint screen, then work outward instead of pushing lint deeper
Clean the lint screen completely and check that it seats correctly. If drying times have become longer, clothes are unusually hot, the laundry room feels humid, or little air reaches the outside hood, treat the problem as restricted exhaust rather than a cosmetic flap issue.
With the dryer off, inspect the exterior hood for lint mats, insect nests, paint, ice, or a bent flap that prevents free movement. Do not remove a pest guard or safety feature unless the replacement hood is designed for dryer exhaust.
- Clean the lint screen and confirm the dryer is not overloaded.
- Observe the exterior flap during a short dryer run from a safe position.
- Turn the dryer off and remove visible lint or debris from the exterior hood without pushing it into the duct.
- Inspect the accessible duct behind the dryer for crushing, sharp kinks, or a disconnected joint.
- If airflow is still weak, stop using the dryer until the full exhaust path can be cleaned and inspected.
A stuck flap and a blocked duct are not the same repair
If strong airflow reaches the hood but the flap barely moves, the hood itself may be painted shut, warped, corroded, iced, or mechanically damaged. If almost no air reaches the hood, the restriction is more likely upstream in the duct, at a joint, or inside the appliance.
CPSC notes that lint buildup in the dryer or exhaust duct can block airflow, increase heat, and contribute to dryer fires. Do not keep adding cycle time to compensate for poor exhaust.
Choose replacement vent parts for airflow, not for a tighter seal
If the exterior hood needs replacement, match the dryer manufacturer's required duct diameter and termination style. The damper should open freely under dryer airflow and close when the dryer is off without using a screen that can quickly pack with lint.
For the connecting duct, follow the dryer manual and local requirements. Avoid makeshift plastic or foil solutions where the manufacturer calls for rigid or semi-rigid metal ducting. If you have a gas dryer, do not move or disconnect the appliance far enough to strain the gas connector.
Before you call it done
- The exterior flap was observed during actual dryer airflow from a safe location.
- The lint screen and exterior hood were cleaned without pushing lint deeper into the duct.
- Accessible ducting was checked for crushing, kinks, disconnection, or heavy lint buildup.
- Longer drying time, excess heat, or weak exterior airflow is being treated as an exhaust restriction rather than ignored.
- An inaccessible or still-restricted vent path is being professionally cleaned or inspected before regular use resumes.