High efficiency air filter as the filter end, so the requirements for HEPA filters are the most strict, the factory required by testing. HEPA filter is the filter at the end of the most critical level, require additional "observing". To extend the life of the HEPA filter, the most fundamental way is to trap dirt out of the filter. Replacement pre-filter without production, no need to debug, so experienced owners will turn their attention and money on the pre-filter. Class 10,000 and class 100,000 clean room. Filter F8 filters, HEPA filters at the end of service life of up to five years. In overseas projects and the new projects, the F8 filters non-uniform flow in clean room the most common pre filter. For chip plant level 100, level 10 or higher level clean room, common pre filter efficiency level for the H10, a number of new projects using HEPA. Design of HVAC system in China in the past, filters for common configuration is: coarse medium efficiency efficient. Then the life of HEPA filters for 1--3 year, the worst for several months. Visible, filter efficiency decisions filter used at the end of life.