How to Choose High-Efficiency Filters for Cleanrooms
The core of selecting high-efficiency (HEPA/ULPA) filters for cleanrooms is to follow the four-step process: "cleanroom classification → filtration efficiency → working condition adaptation → compliance", balancing filtration performance, service life, and system compatibility to avoid waste from blind pursuit of high parameters.
1. Core First: Match Cleanroom Classification with Filtration Efficiency
This is the foundation of selection. Corresponding filter efficiency (per EN 1822 standard) with ISO 14644 cleanroom classification (Class 1-9) to avoid insufficient efficiency or over-filtration:
ISO Class 5 (Class 100) and above: Choose H13/H14 high-efficiency HEPA filters (filtration efficiency ≥99.97%/99.995% for particles ≥0.3μm). U15/U16 ultra-high efficiency ULPA filters are required for core areas.
ISO Class 6-8 (Class 1,000 - 100,000): Mainly select H11/H12 HEPA filters, with G4/F5 primary filters and F7/F8 medium-efficiency filters at the front end to form a three-stage filtration system.
Key reminder: High-efficiency filters must specify "MPPS (Most Penetrating Particle Size) efficiency" instead of only "0.3μm efficiency", which is more in line with international testing standards.
2. Adapt to Working Conditions: Select Materials and Structure Based on Usage Environment
The temperature, humidity, and pollutant types of the cleanroom directly affect filter stability:
Normal working conditions (20-25℃, humidity ≤80%): Choose glass fiber filter paper (core material for HEPA, with stable efficiency and large dust-holding capacity) and aluminum alloy frames (lightweight and rust-proof).
High temperature and humidity (e.g., reflow soldering areas in electronics factories, humid heat sterilization areas in pharmaceuticals): Select glass fiber filter paper resistant to ≥120℃, stainless steel frames (corrosion-proof), and silicone sealant (high-temperature aging resistance).
Chemical pollutants (e.g., chemical, semiconductor cleanrooms): Choose PTFE-coated glass fiber filter paper (acid and alkali resistant, hydrophobic and oil-proof) to avoid filter paper corrosion and failure.
Structural selection: Non-separated HEPA (small size, good sealing) for high cleanroom classes (ISO Class 5 and above); separated HEPA (low wind pressure loss, higher dust-holding capacity) for large air volume systems.
3. Key Details: Match System Parameters and Installation Requirements
Filters must be compatible with the cleanroom's HVAC system, otherwise operational efficiency will be affected:
Air volume matching: Select based on the filter's rated air volume. The actual operating air volume should be within ±10% of the rated value to avoid reduced filtration efficiency and increased noise due to excessive air volume.
Wind pressure loss: Prioritize products with low initial resistance (≤250Pa@rated air volume) to reduce HVAC system energy consumption and extend fan service life.
Installation sealing: Choose filters with integral polyurethane foam gaskets. For installation, use pressure strips or liquid tank sealing (essential for high cleanroom classes) to prevent air leakage (leakage rate ≤0.01%).
Custom size: Customize according to the cleanroom ceiling keel spacing or air duct size to avoid sealing failure caused by on-site cutting.
4. Compliance and Quality: Avoid Hidden Risks
Cleanrooms are mostly used in pharmaceuticals, electronics, medical and other industries, requiring compliance with industry specifications:
Qualification certification: Must provide EN 1822 (European) or ANSI/ASHRAE 52.2 (American) certification reports, specifying key indicators such as efficiency class and leakage rate.
Industry-specific requirements: Pharmaceutical industry must comply with GMP standards, with filters free of fiber shedding and sterilizable; electronics industry requires anti-static properties (to prevent electrostatic dust adsorption).
Brand and after-sales: Choose brands with specialized cleanroom filtration qualifications, request factory inspection reports (DOP/PAO leak test certificates), and ensure post-replacement guidance is available.
