What are the differences between pre-filters, secondary filters and fine filters?

Pre-filters, fine filters and HEPA filters are also filters. What are the differences?

1.  Functions

Pre-filters are used for filtering dust particles above 5μm, suitable for primary filtration of air conditioning system.

Fine filters are belongs to the group F of air filters, and is generally bag filter, including class F5, F6, F7, F8 and F9. Medium efficiency filter is widely used in air conditioning system, mainly used to filter dust particles over 1-5 μ m.

HEPA filters are mainly used to capture particulate dust and various suspended substances, with the particle size below 0.5 μ m.

2. Filter media

Pre-filters: The outer frame material includes paper frame, aluminum frame and galvanized iron frame, and the filter media includes non-woven fabric, nylon mesh, activated carbon filter material and metal mesh.

Fine filters: bag filter, frame filter, combined filter, etc.

HEPA filters: ultra-fine glass fiber paper is used as the filter media, offset paper, aluminum film and other materials are used as the partition board, which is glued with wood frame and aluminum alloy.

3. Class and filtration efficiency

Pre-filters: G1-G4, 5 μ m, 65%, 80%, 90%, 95%.

Fine filters: F5-F9, 1 μ m, 60%, 70%, 80%, 90% and 95%.

HEPA filters: H10—H14, MPPS, 95%, 99.5%, 99.95%, 99.995%, 99.9995%.