The purpose of air filter is to obtain clean air that can reach the standard. The general ventilation filter is to capture and absorb dust particles of different sizes in the air, so as to improve the air quality. Besides adsorbing dust, chemical filter can also absorb odor. It is usually used in biopharmaceuticals, hospitals, airport terminal buildings, human settlements and other places. General ventilation filters are widely used in microelectronics industry, painting industry, food and beverage industry and so on. In other words, the filter is only a means to achieve the goal of cleanliness.