"Exhaust Fan" is rotationally driven by a motor driven fan airflow, so that a type of air of indoor and outdoor air exchange regulation appliances. Also known as the ventilation fan. The purpose is to remove exhaust polluted indoor air, adjusting temperature, humidity and sensory effects. This air fan widely used in homes and public places. This fan air intake and exhaust ports divided by partition type, type exhaust duct, air intake duct, fully catheter type (according to the air flow into the form of centrifugal, axial flow and cross-flow.