Air filters are mainly used in pneumatic machinery, internal combustion engine machinery and other fields. Its function is to provide clean air for these mechanical equipment to prevent these mechanical equipment from inhaling air with impurity particles during operation, thereby increasing wear and damage. probability. The main components of an air filter are the filter element and the housing. The filter element is the main filter component, responsible for filtering the gas, and the housing is the external structure that provides the necessary protection for the filter element. The working requirement of the air filter is to be able to perform high-efficiency air filtration, without increasing the excessive resistance to the airflow, and to be able to work continuously for a long time. HEPA filter paper is a common filter screen for air filters at present. It can purify particles above 0.3 microns with a removal efficiency of 99.7%, especially for pm2.5. It is a filter highly recognized by consumers. However, in order to maximize the energy efficiency of HEPA filter paper, special attention should be paid to selecting the grade and standard of HEPA filter paper, because the size and grade of HEPA filter paper can be affected by various factors such as the design of the purifier itself and the air flow rate. If it is an air purifier produced by a low-quality manufacturer, although HEPA filter paper is used, the outer layer of the purifier is unreasonably designed and the material is poor, which will cause leakage at the edge of the filter material and affect the filtration effect of the HEPA filter paper filter. As we all know, the adsorption capacity of activated carbon is strong, but the effect of activated carbon alone is not obvious, and another technology is needed to maximize the effect of activated carbon. Now some manufacturers have proposed a new type of nano-photocatalyst - activated carbon fiber composite filter medium, which uses the adsorption capacity of activated carbon particles to absorb all the toxic and harmful gases in the air on the surface of the activated carbon carrier, and then remove these gases. Activated carbon can adsorb gases below 0.3 microns, which is stronger than HEPA filter paper. Easy to clean, can be washed directly. But activated carbon needs to be replaced once a year to avoid the decline of activated carbon adsorption capacity.