There are two types of air filters, dry and wet.
　　Dry
　　Is through a dry filter, (such as paper filter) to separate impurities in the air filter. Air cleaners for light vehicles (including passenger cars and mini vehicles) are generally single-stage. Its shape is oblate or oval and flat. The filter material is filter paper or non-woven fabric. Filter cover with metal or polyurethane, the shell material is metal or plastic. In the rated air volume flow, the original filter efficiency of not less than 99.5%. Heavy-duty vehicles due to poor working conditions, its air filter must be the most. The first stage for the pre-cyclone filter (such as blade ring, cyclone, etc.) for the removal of coarse particles of impurities, filtration efficiency of 80% or more, the second fine filter is a porous paper filter (commonly known as the Lord Filter), the filtration efficiency of more than 99.5%. After the main filter there is also a safety filter, its role is to prevent dust from entering the engine when installing and replacing the main filter, or when the main filter is accidentally damaged. The material of the safety core is mostly non-woven fabric, but also the use of filter paper.
　　Wet
　　Including oil-immersed and oil bath two. Oil-immersed through an oil-impregnated filter, the air impurities separated, the filter material is a metal wire fabric, but also foam material. Oil bath is to inhale the dusty air into the oil pool to remove most of the dust, and then with the mist of air up through a filter made of wire for further filtration, the oil droplets and was stopped Dust to return to the sump.
　　This article by the Dongguan Heyi filter Technology Co., Ltd. finishing.