For air filters for general ventilation, there are two classification standards in China: GB 12218-89 "performance test methods for air filters for general ventilation" and GB 14295-93 "air filters"
According to the test of more than 100 kinds of air filter materials and filters with different processes and materials and the analysis of the technical performance data of some foreign products, some people in China put forward the classification method of air filter according to the counting efficiency of atmospheric dust in 1980, as shown in table 5.2. It also has certain practical significance for the classification of filters.