Lint and debris can build up in the clothes dryer vent blocking air flow and creating potentially hazardous conditions including the possibility for an exhaust fire or carbon monoxide intrusion (gas clothes dryers). "The U.S. Fire Administration, National Fire Data Center reports that there are over 12,700 home fires per year associated with clothes dryer fires resulting in 15 deaths and 300 injuries, and 88 million dollars in property loss."
Along with the water vapor evaporated from the wet clothes, the exhaust stream carries lint – highly flammable particles of clothing made of cotton and polyester – through the ventilation duct. Lint can accumulate in the exhaust duct, reducing the dryer’s ability to expel the heated water vapor, which then accumulates as heat energy within the machine. As the dryer overheats, mechanical failures (thermostat, limit switch, damaged screen, or crushed hose) can trigger sparks which cause the lint trapped in the dryer vent to burst into flames.