1. The main parameters selected for the HEPA filter include: filtration efficiency, rated air volume, initial resistance under rated air volume, dust holding capacity, etc.

2. According to the method stipulated in GB/T6165-1985 "Performance Test Method for High-Efficiency Air Filters - Transmittance and Resistance", a filter is considered a high-efficiency air filter if its transmittance is ≤ 0.1% (i.e., efficiency ≥ 99.9%) or the count transmittance of particles with a diameter ≥ 0.1 μm is ≤ 0.001% (i.e., efficiency ≥ 99.999%).

3. Common filter materials for high-efficiency air filters include ultra-fine glass fibers, PTFE, etc.

4. Air filters should meet fire protection requirements. High-efficiency air filters are classified into three levels based on their fire resistance: 1st level filter, where all materials of the filter are non-combustible, and non-combustible materials should comply with GB8624-1997 A grade. 2nd level filter, where the filter material should be non-combustible materials that comply with GB8624-1997 A grade, and the partition plates and frames can be made of combustible materials that comply with GB8624-1997 B2 grade. 3rd level filter, where all materials of the filter can be made of combustible materials that comply with GB8624-1997 B3 grade.

5. During design, the final resistance can be set as twice the initial resistance as the calculation resistance for the filter.

6. The initial resistance of high-efficiency air filters should not exceed 10% of the resistance indicated in the product sample.

7. High-efficiency air filters should not be used alone. They are preferably set at the end of the purification air conditioning system.

8. High-efficiency filters should be inspected for leaks upon leaving the factory. Other requirements can be determined according to user needs.

9. In general non-parallel flow clean air conditioning systems, combined filter air outlets are commonly used.

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