The air filter is located in the engine intake system and is an assembly composed of one or several clean air filter components. Its main function is to filter out harmful impurities in the air that will enter the cylinder, To reduce the early wear of cylinder, piston, piston ring, valve and valve seat. There are two types of air filters, namely dry and wet.

A dry air filter is a filter that separates impurities from the air through a dry filter element, such as a paper filter element. The air filters used in light vehicles (including sedans and micro cars) are generally single stage. It has flat, elliptical, and flat shapes. The filtering material is filter paper or non-woven fabric. The end cover of the filter element is made of metal or polyurethane, and the outer shell material is metal or plastic. At rated air volume flow rate, the original filtration efficiency of the filter element should not be less than 99.5%. Due to the harsh working environment, heavy-duty vehicles must have a majority of air filters. The first stage is a swirling pre filter (such as blade rings, swirling tubes, etc.) used to filter out coarse particles and impurities, with a filtration efficiency of over 80%. The second stage of fine filtration is a microporous paper filter element (commonly referred to as the main filter element), with a filtration efficiency of over 99.5%. After the main filter element, there is also a safety filter element, which is used to prevent dust from entering the engine when installing and replacing the main filter element, or when the main filter element is accidentally damaged. The material of the safety core is mostly non-woven fabric, Some also use filter paper.