(1)Usually, filters of the same material ，the higher efficiency the larger resistance and the price is also higher.

(2)Cleanrooms with high cleanliness requirements can choose HEPA or ULPA filters with high efficiency, and cleanrooms with low cleanliness requirements can choose HEPA filters with low efficiency.

(3)The change of filter efficiency under high dust generation has little effect on the cleanliness of the clean room, so a clean room with low cleanliness requirements should not choose a high-efficiency high-efficiency filter.

(4)Under low dust generation, high-efficiency filters with higher efficiency have significant benefits for cleanliness at low wind speeds. Therefore, for clean rooms that require high cleanliness, while selecting high-efficiency filters, it is necessary to reduce their head-on wind speed.