The development of air filters
An air filter is a device that filters suspended particles in the air. The prototype of the filter is a respiratory protective device used by people to protect their breath, and its rapid development is closely related to the development of military and electronic industries. During World War I, military gas masks using asbestos fiber filter paper as a smoke filter layer emerged due to the use of various chemical toxins. In World War II, with the development of the atomic energy industry, the current filter paper air filter was developed to remove radioactive particles.

Air filter element
The United States established a dedicated filter paper development team in 1942. Developed a mixed fiber filter material of wood fiber, asbestos, and cotton, with a filtration efficiency of 99.96%, which is the prototype of the current Hepa filter. Subsequently, glass fiber mixed filter paper was developed and applied in atomic energy technology. At that time, the material used to make filter media was cellulose, but this material had issues with fire resistance, moisture absorption, and other aspects. Currently, the filter material for air filters is mainly made of fiberglass.
The performance of an engine air filter is primarily related to the filter material used. It is also related to the structure of the filter itself and the quality of the filter element/JUT. The first requirement for filter media is good breathability to ensure low flow resistance of the filter element. Secondly, the porosity is appropriate to ensure sufficient filtration efficiency and fineness.

The most widely used filter material for engine air filters is resin treated microporous filter paper. The pulp of filter paper is treated with mercerization, and the fibers are curled and soft, making the resulting filter paper porous and loose. In addition, resin treatment not only enhances the mechanical strength of the filter paper itself, but also improves its water resistance. Therefore. Microporous filter paper has become the most reliable and widely used filter material for engine air filters.

Car air filters are the main components that ensure high cleanliness of the air entering the engine cylinders. Therefore, it is required that the filter material has good breathability and appropriate porosity, but these two requirements are contradictory to each other. Generally, different filter media are used to meet the needs of different air filters. To ensure filtration efficiency, regardless of the type of filter material used, the future development of automotive engine air filters will be towards low consumption, low cost, large intake volume, high ash storage capacity, good water resistance, and high filtration accuracy.