A clothes dryer requires air-flow to do its job; the dryer vent and duct system is responsible for carrying the hot, moist air and lint from the wet laundry in the dryer drum to the outdoors. Only about 60 percent of the lint is caught in the lint screen; the rest goes through the dryer ducts; some makes it outside through the vent. The rest is trapped somewhere in the dryer duct.
A clothes dryer fire occurs when lint accumulates restricting airflow which then leads to overheating. Heat and lint are the main ingredients for a clothes dryer fire. Lint is combustible; therefore, fuel for a fire to spread rapidly.

Another issue is the length of the vent; the shorter, the better. It used be that most clothes dryers were in the basement, on an outside wall, with a relatively short, straight vent to the outdoors. These days many newer homes tend to have their laundry area located away from an outside wall; some are on the second floor. This means dryer vents are much longer and contain some bends where lint can accumulate. They're also harder to reach therefore more difficult to keep cleaned. The ideal dryer vent system is short and straight. The pieces should also be joined together to leave the inside smooth and free of screws or fasteners that lint can catch on.
It is important that the venting be made of rigid material, not the flexible, foil type tubing that crushes easily, restricting airflow. Allow enough clearance between the clothes dryer and the wall; some people push the dryer too close, crushing the venting and creating an air flow problem right off the bat.
Jon Perry is the owner of Dryer Vent Wizard, a dryer vent cleaning, repair and installation specialist who serves consumers in Central California. Jon is committed to preventing fires in his community as he takes the time to educate his customer on dryer vent cleaning and maintenance to prevent fires and save energy. Visit http://www.dryerventwizard.com to schedule a dryer vent inspection to be sure your dryer is safe.