According to the Federal Emergency Management Agency, over 15,600 fires requiring a fire department response start each year in homes. Most are caused by clogged lint traps and vents in clothes dryers.
Dryers work by forcing hot air through the drum. That air carries lint with it which is filtered by the lint trap. If that trap isn't cleaned regularly, the flow of hot air is restricted. As the air heats up, it can eventually ignite the lint buildup.