How does a dryer fire start?

A. Dryer vents accumulate lint just like plaque deposits that form in human blood vessels. The lint reduces air flow and increases clothes drying times. The lint can build-up to the point where it blocks the dryer exhaust and causes serious overheating in the dryer. When this happens, the dryer's high temperature safety switch will repeatedly cycle on and off. Ultimately, the safety switch can fail, allowing the highly flammable lint to ignite. Investigators have found that just a single spark can ignite lint. We've seen dryers whose housings were packed with lint--often, the lint is charred black and a heartbeat away from starting a house fire!.  more