Between 2010–2014, U.S. municipal fire departments responded to an estimated 15,970 home fires involving clothes dryers.
According to the US National Fire Protection Association The very leading cause of dryer fires is from forgetting to clean and clear the dryer vents. Dryer vents can build up with lint which will cause an issue with ventilation. The lack of ventilation causes heat to build up which can ignite into a fire.
Most of these home fires involved clothes dryers (92%) Souce: NFPA
Early detection of lint accumulation can prevent dangerous dryer fires from occurring. Some of the clues that might show your dryer vent needs to be cleaned are: