Dryer lint is wet when it wases initially eliminated from laundry, so very little will make to the vent outdoors. It ends up being stuck to the sides of the dryer vent tube where it dries to a hard paste and draws in more lint with each load of laundry. As the lint builds up, airflow is limited and the clothes dryer should work harder and longer to dry each load. This increases energy costs and can result in malfunction, breakdown or a clothes dryer fire. Though failure to clean clothes dryer vents is the leading reason for fires, incorrect dryer vent installation or use of the inexpensive vinyl kits sold in hardware stores can also result in hazardous conditions.