How To Select Primary, Medium And High-Efficiency Air Filters for Clean Rooms

Clarify the cleanliness class requirements of the clean room

1. Determine the clean room's cleanliness class (e.g., ISO Class 5, Class 7) in accordance with international standards (such as ISO 14644-1) or industry specifications (such as GMP standards for the pharmaceutical industry).

2. The higher the cleanliness class, the stricter the filter efficiency requirements, and it is usually necessary to use a combination of higher-efficiency filters.

Selection and matching of the three-stage filtration system

1. Primary Filter

Function: Capture large particulate dust (≥5μm), protect subsequent filters and extend their service life.

Recommendation: Select G3/G4 (per EN779 standard) or MERV 5-8 (per ASHRAE standard) primary filters, mostly made of polyester fiber or non-woven fabric.

Application scenario: Served as the first-level protection, commonly used at the air inlet of fresh air systems or air conditioning units.

2. Medium Efficiency Filter

Function: Filter medium-sized particles (1-5μm), such as dust, pollen, etc.

Recommendation: Select F5-F9 (per EN779 standard) or MERV 9-16 medium efficiency filters, usually made of glass fiber or synthetic fiber.

Application scenario: Installed after the primary filter and before the high-efficiency filter to protect the high-efficiency filter.

3. High-Efficiency Filter (HEPA/ULPA)

Function: Capture micro-particles (≥0.3μm), such as bacteria, viruses, submicron particles, etc.

Recommendation:

HEPA: H13 (filtration efficiency ≥99.97% @0.3μm) or H14 (≥99.995% @0.3μm), suitable for ISO Class 5-7 clean rooms.

ULPA: U15-U17 (filtration efficiency ≥99.9995% @0.12μm), suitable for clean rooms with higher cleanliness requirements (e.g., ISO Class 3-5).

Material: Ultra-fine glass fiber filter paper; airtightness must be ensured (e.g., gel seal or knife-edge seal design).

Key selection factors

1. Filtration efficiency and standards

Confirm that the filter complies with international standards (such as EN 1822, IEST RP-CC001.5, etc.) and avoid using non-standard products.

2. Air volume and pressure drop

Select the rated air volume of the filter according to the circulating air volume of the clean room, and ensure the pressure drop is within the bearable range of the system (excessively high pressure drop will increase energy consumption).

3. Material and structure

High-efficiency filters need to be high temperature and moisture resistant (e.g., sterilization may be required in the pharmaceutical industry); primary and medium efficiency filters need to be easy to replace and anti-aging.

4. Antibacterial/chemical corrosion resistance requirements

For use in biological laboratories or chemical environments, select filters with antibacterial coating or corrosion-resistant materials.