Abstract: The present invention generally relates to an apparatus for preventing the accumulation of snow, ice, frost, hail or the like from obstructing the flow of primary air, air or the exhaust of sewer gas into or out of a building. The apparatus is also suitable to prevent leaves, animals or other debris from becoming trapped within the air flow pipes of the building. The apparatus has a screen which may be electrically connected to a heating device. The apparatus may further be attached to a thermostat to automatically turn the heating device on or off at preset temperatures. The apparatus may be incorporated into new pipes or may be attached onto existing pipes.