Exhaust ducts carry humid air from bathroom fans, kitchen fans, and dryers to the outside, and need to function properly to ensure healthy indoor air quality. It is important to seal ducts penetrating through walls in rooms with elevated humidity levels, such as bathrooms, as the amount of water that could condense inside the exterior wall through air leakage is high.

Exhaust ducts should be installed to drain condensation build-up to the outdoors, and filters should be accessible so the occupants can perform regular cleaning to avoid blockage.

This air sealing procedure is for metal exhaust vents that extend through above-grade walls.