Dryer vent covers are effective way to prevent animal or insect access to the dryer vent and a way to save energy. Vent covers also allow the free escape of air and lint, making them much less of a fire hazard. By allowing the vent opening to shut when the dryer is not in use, dryer vent covers prevent cold air from entering the home in winter or air-conditioned air from leaving home in summer months. The average dryer dries clothes by sucking in air from the surrounding room into the dryer. This air is pass through a heating element that heats the air. That heated air is pulled or forced through a rotating "drum" that holds the wet clothes. An exhaust vent in the dryer forces this heated air, which turns to steam as it is drawn through the wet clothing, to pass out of the dryer. The stream contains lint, small fibers of the fabric released from the clothing during the whole drying process. Some of this lint gets past the lint filter, especially if the filter isn't cleane