How to Find Where a Dryer Vent Goes

Where a Dryer Duct Is Allowed to End

The search is easier once you know the possible answers. The 2023 Florida Building Code, Residential, section M1502.3 says a dryer exhaust duct terminates on the outside of the building. Section M1501.1 rules out an attic, soffit, ridge vent or crawl space. So a correctly built duct ends in one of three places: a hood on an outside wall, a cap on the roof, or, in a slab house, a duct under the floor that comes up outside.

Anything else, a duct that stops in the attic, under a ridge vent or inside a wall, is not a hidden exit you have failed to find. It is an exit that was never built.

First, Run the Dryer and Look Outside

The fastest test is the one the CPSC recommends for routine checks: run the dryer and look at the outside vent to make sure exhaust air is escaping. Start a load on heat, wait a few minutes, then walk the outside walls of the house. Whirlpool's instructions suggest running it 5 to 10 minutes and holding a hand under the hood to feel the air.

Look first on the wall nearest the laundry, then on the other walls at the same end of the house, then up at the roof above the laundry and along the likely path across the attic. A flap that lifts and a stream of warm, damp air mark the exit. On a roof cap you can watch from the yard; there is no need to climb.

• Outside wall behind or near the laundry: a hood with a flap.
• Other walls at that end of the house, including gable ends.
• The roof above the laundry and along the attic route: a low cap with a flap.
• Ground level near the slab edge, for an under-slab duct.
• Under the eaves: if you find it here, read the soffit note below.

Next, Read the Clues Behind the Dryer

Unplug the dryer and pull it out. The transition hose goes from the dryer outlet to a collar in the wall, floor or ceiling, and section M1502.4.3 says that hose may not be hidden inside the construction. The collar tells you the first direction: a wall collar usually means a short run out that wall or a climb inside it, a ceiling collar means the attic, and a floor collar in a slab house means the duct runs under the slab.

Look for a label too. Under section M1502.4.6, when a run's equivalent length is over 35 feet, a permanent label or tag within 6 feet of the duct connection must say so. A label there tells you the duct is long, and often that it goes up and across the attic.

Then Follow the Duct Into the Attic

If the collar points up, the duct is in the attic. Go up only if you can move safely: stay on the framing, take a light, keep clear of wiring and nails, and avoid the attic in the heat of the day. Find the duct where it rises from the laundry wall and follow it by eye. It will either reach a gable or side wall, rise to the roof deck, or stop.

While you are there, note any joint that has pulled apart or any grey lint on the insulation. Those findings matter as much as the route.

The Under-Slab Route You Cannot See

Section M1502.4.1 allows one exception to metal duct: 4 inch Schedule 40 PVC installed horizontally beneath the slab. In a slab house with a floor collar behind the dryer, the duct runs under the floor and turns up outside the foundation to a hood near the ground. Look along the outside wall closest to the laundry, near ground level, while the dryer runs.

A Missing Exit, and What It Means

If no hood or cap moves with the dryer running and the duct stops inside the house, the exhaust is going somewhere it should not. GE's installation instructions say a dryer must not be exhausted into a wall, a ceiling or any concealed space of a building that can accumulate lint, because that creates a fire hazard. A duct ending in the attic or under a ridge vent also breaks section M1501.1, and it fills the attic with damp air and lint.

Two other cases look like a missing exit but are not. A duct capped behind the dryer and marked 'future use' is allowed by section M1502.4.7 when no dryer was installed; it still needs a real exit before a dryer goes on it. And a duct ending at a soffit vent or behind eave screening is a soffit exit, which our guide on venting through a soffit explains. If you are unsure what the cap on your roof is, see how to spot the dryer vent on a roof.

When We Trace It for You

Stop and call if the duct disappears into a wall or floor you cannot follow, if you find lint in the attic, or if no exit moves with the dryer running. Our experienced technicians trace hidden ducts for a company that is locally owned, family-owned and Proudly American. A free inspection traces the duct from the dryer to wherever it ends and comes with a written estimate.

Once the route is known, a duct that only needs lint cleared is a dryer vent cleaning job. A duct with no proper exit needs a new run, and our Proudly American installers will show you the shortest one before quoting it.