Yitong Bag Type Air Filter has been applied in many industries,like pharmacy, automotive and food manufacturing industry, and other industries for the ventilation system usage. There are 7 grades of the filteration efficiency, like G3, G4, F5, F6, F7, F8 and F9 grades. The bag filters are designed for the HVAC system, for it has the large filteration area, large dust holding capcity, low resistance and etc,. It is commonly seen in the HVAC system for industrial and commercial apolications. Nowadays peolple are more concentrate on th e indoor air quality, the bag air filter are also seen in the residential areas.