The roles of air filters at all levels are:

Primary effect filter: mainly used to prevent 10μm settled particles carried by fresh air and various foreign objects from entering the system.

Intermediate-effect filter: mainly used to block 1-10μm suspended particles, so that they do not settle on the surface of the high-efficiency filter, rapid clogging of the high-efficiency filter.

High-efficiency filter (sub-high-efficiency filter): the air filter is mainly used to filter most of the components in the air supply that cannot be filtered or are difficult to be filtered by the coarse-efficiency filter and the medium-efficiency filter. Particles below 1μm can be removed to control the critical final part of the air supply system.

Since the various air filters mainly filter particles of different sizes and the filtration efficiency varies greatly, the filters should be categorised according to the efficiency ranges of the different measurement methods