The following advice can help
you prevent a disaster.

When it comes to dryer fires, flexible dryer ducts made of foil or plastic are the most problematic because they can sag and let lint build up at low points. Ridges can also trap lint. Metal ducts, neither flexible or rigid, are far safer because they don't sag, so lint is less likely to accumulate. What's more, if a fire does start, a metal duct is more likely to contain it.

Anatomy of a Dryer Fire

Dryer fires usually start beneath the dryer when the motor overheats. Overheating is caused by a build-up of lint in the duct that increases the drying time and blocks the flow of air. Naturally, any lint that has collected under the dryer will burn and the draft from the dryer will pull that fire up into the duct. Since the duct may be coated or even blocked with lint, many times a house fire results. Other contributing conditions may include failure of the thermostat and limit switches in the dryer, lint inside the dryer, a missing or damaged lint screen, a crushed hose behind the dryer, or a bird's nest or other debris blocking the vent.