"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. Fan widely used in homes and public places. Product also known as suction fan, negative pressure fan. Is the use of air convection allows the interior has been in a state of negative pressure, the formation of a suction, a steady stream of inhaled outdoor air and indoor hot exhaust air to achieve ventilation, cooling effect.