Dryer vent
The duct that carries hot, lint-filled air from your dryer outdoors.
The dryer vent is the duct running from your clothes dryer to the outside. Lint escapes the lint trap and builds up inside it, and lint is highly flammable — clogged dryer vents cause thousands of house fires a year. Clean the full duct annually, and if drying takes longer than it used to, clean it sooner.