The U.S. Fire Administration attributes roughly 2,900 residential fires each year to clothes dryers, with lint buildup being the leading cause. The mechanism is simple: lint is highly flammable, and dryers get hot.
Lint accumulates in three places: the lint screen, the transition hose behind the dryer, and the exterior vent duct. The screen you can handle yourself. The other two collect year after year until airflow is restricted.
Restricted airflow means the heating element cycles longer, the dryer works harder, and internal temperatures rise. Eventually, lint ignites.
The prevention is straightforward: clean the full vent run — not just the first few feet — once a year. Confirm airflow with an anemometer. Replace old, damaged, or foil-style transition hoses with rigid metal.