The air filter mainly uses the filtration separation method: Through the setting different performance filter, eliminates the airborne suspended dust particle and the microorganism, also namely passes through the filter material to gather the dust particle to intercept, guarantees sends the air volume cleanliness request. It uses the filter material for the finer diameter of the fiber, both can make the air flow smoothly through, but also can effectively trap dust particles in the direction of the air inlet in order to filter, pressure reducing valve, oil mist device. Air filters are generally used in clean workshops, clean workshops, clean rooms, laboratories and cleanroom, or dust-proof for electronic mechanical communication equipment. Has the coarse effect filter, the medium efficiency filter, the high efficiency filter and the high-efficiency and the high efficiency filters altogether five kinds of models. Compressed air from the gas source contains excessive water vapor and oil droplets, as well as solid impurities, such as rust, sand, pipe sealant, etc., these will damage the piston seal ring, plug the small exhaust holes in components, shorten the service life of components or make it ineffective. The purpose of the air filter is to separate the liquid water from the compressed air, the liquid oil droplets, and to filter the dust and solid impurities in the air, but not to remove the gaseous water and oil. Three is an indispensable gas source device in most pneumatic systems, which is installed in the vicinity of the gas equipment, is the final guarantee of compressed air quality, its design and installation, in addition to ensure the quality of three itself, but also to consider the space saving, easy to operate installation, can be arbitrary combination and other factors.