Classification of Air Filters

The function of a car's air filter is to filter the air entering the engine to ensure proper engine operation and to prevent harmful emissions into the environment.

Dry air filters are filters that separate impurities from the air through a dry filter element . The air filter used in light-duty vehicles is usually a single-stage filter. Its shape is flat and round or elliptical and flat. The filtering material is filter paper or non-woven fabric. The end caps of the filter element are made of metal or polyurethane, and the housing material is metal or plastic. Under the rated air flow rate, the initial 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 large number of air filters. The first stage is a cyclone pre-filter , which is used to filter out coarse particulate impurities with an efficiency of more than 80%. The second stage is the fine filtration with a microporous paper filter element , with a filtration efficiency of more than 99.5%. Behind the main filter element is 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 element is mostly non-woven fabric, and some also use filter paper.

Wet air filters include oil-immersed and oil-bath types. The oil-immersed filter separates impurities from the air through an oil-immersed filter element, which is made of metal wire mesh and foam material. In the oil-bath type, the inhaled dust-containing air is introduced into the oil pool to remove most of the dust, and then the air with oil mist is filtered further when flowing upward through the metal wire-wound filter element. The oil droplets and captured dust are returned to the oil pool together. Oil-bath air filters are now commonly used in agricultural machinery and ship power

To maintain normal operation of a car, it is recommended to regularly replace the air filter. Generally, the dry air filter should be replaced every 10,000-20,000 kilometers or every six months, and the wet air filter should be replaced every 50,000 kilometers.