The preliminary-efficiency filter media is made of PET fiber and can be divided into non-glue non woven and glue-spray non woven according to the process.. The non-glue non woven is baked based on the combination of ordinary PET fiber and ES fiber(low melting point polyester fibre), and it may use fiber of different degree of thickness to make the filter non woven of thickness of 5-30mm to guarantee different filtration effects. The filtration can be divided into G1, G2, G3, G4 and F5 according to European filtration classification and preliminary-efficiency, medium-efficiency and medium-high efficiency filtration according to China's filtration classification, which is commonly used in panel air filter and pleating panel filter. The main characteristics is large air flow, small resistance, solid structure and can be repeatedly cleaned.