The dryer vent glossary.

Backdraft damper

A flap in the vent hood that opens when the dryer runs and closes when it stops to keep out air, pests and weather.

Booster fan

An inline fan made for dryer exhaust that helps move air through a long run, where the dryer maker and local code allow it.

BTU

British thermal unit, a measure of heat. Gas dryers are rated in BTU per hour.

Carbon monoxide (CO)

A colorless, odorless gas made when fuel burns. A gas dryer's exhaust must leave through a clear vent.

CFM

Cubic feet per minute, a measure of how much air a fan or a vent moves.

Clamp

A metal band that holds a duct to a connection. Preferred over screws, which catch lint.

Condensation

Water that forms when warm, damp air cools inside a cold duct.

Damper

See backdraft damper.

Dryer vent hood

The cap on the outside wall or roof where the dryer exhaust leaves the building.

Duct

The tube that carries air. A dryer duct carries warm, damp air and lint to the outdoors.

Effective length

The straight length of a duct plus an allowance for each bend, used to compare a run with the planning limit.

Elbow

A bend in a duct. Each elbow slows the air and gives lint a place to settle.

Exhaust

The air the dryer pushes out through the vent.

Foil tape

A metal tape made for sealing duct joints. Preferred over cloth duct tape, which dries out and fails.

Flexible duct

Thin foil or vinyl duct that bends easily but crushes, sags and traps lint in its ridges.

HVAC

Heating, ventilation and air conditioning, the system that heats, cools and moves air through a home.

Lint

Tiny fibers shed from clothes and towels that collect in the lint screen and the vent.

Lint screen

The mesh in the dryer that catches lint. It should be emptied after every load.

Manometer

A gauge that measures air pressure, sometimes used to check how much a vent restricts airflow.

Plenum

A box in a duct system where air is distributed to several ducts.

Recessed dryer box

A pocket in the wall that holds the duct connection so the dryer can sit close to the wall without crushing the duct.

Register

A vent cover on a wall, floor or ceiling where air from the ducts enters a room.

Return

A duct and grille that pull air from a room back to the heating and cooling system.

Rigid duct

Smooth, solid metal duct that moves air well and holds its shape.

Rotary brush

A spinning brush on a flexible rod used to loosen lint inside a duct.

Semi-rigid duct

Metal duct that bends into curves and holds its shape, often used for short connections.

Static pressure

The resistance air meets inside a duct. A clogged duct has high static pressure.

Supply

A duct and register that push heated or cooled air into a room.

Termination

The place where a vent ends outdoors, usually a hood or a roof cap.

Trap slot

The opening in the dryer where the lint screen sits. Lint can fall into it past the screen.

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