Air Filtration Systems in Cleanrooms: Classifications, Technical Specifications, and Industry Applications

Cleanrooms are specialized environments with stringent air quality standards, widely used across sectors like electronics, biopharmaceuticals, food processing, and precision manufacturing. Central to the performance of any cleanroom is the air filtration system—responsible for controlling airborne particulates, ensuring sterility, and maintaining compliance with ISO standards.

This article provides a comprehensive overview of air filters used in cleanroom environments, exploring classifications, technical benchmarks, configuration strategies, and key maintenance practices, all tailored to real-world industrial applications.

1. Air Filter Classifications & Key Performance Metrics

1. By Filtration Efficiency

• Primary (Coarse) Filters – G-Class
  Efficiency:≥50% for particles ≥5μm (ISO G1–G4)
  Features: Open-structure design, made from synthetic fibers or metal mesh, dust-holding capacity of 500–1500g/m²
  Performance: Initial resistance ≤50Pa; replacement every 1–3 months

• Medium Efficiency Filters – F-Class
  Efficiency:60–95% for particles ≥1μm (ISO F5–F9)
  Features: Available in bag, panel, or modular formats with filtration areas of 3–10m²
  Performance: Initial resistance of 80–120Pa; lifespan of 3–6 months
• High-Efficiency Filters – H-Class
  Efficiency:≥99.97% for 0.3μm particles (ISO H10–H14)
  Features: Mini-pleat or separator designs using glass fiber media with over 50m² filtration area per unit
  Performance: Resistance up to 300Pa; leak testing (PAO scan) must show <0.01% penetration
• Ultra-High Efficiency Filters – U-Class
  Efficiency:≥99.9995% for 0.12μm particles (ISO U15–U17)
  Features: Nano-pleated media with fiber diameters ≤0.3μm; commonly used with laminar flow units
  Performance: Initial resistance ≥300Pa; periodic integrity testing required

1. Specialty Filters

Activated Carbon Filters
Designed to absorb VOCs, odors, and chemical fumes, with iodine adsorption values ≥800mg/g. Ideal for solvent vapor control in pharma or photolithography exhausts.

High-Temperature Filters
Withstand temperatures from 250–400°C, using ceramic or metallic media. Suitable for paint curing ovens, sterilization tunnels, etc.

Antibacterial & Antiviral Filters
Coated with nanosilver or photocatalytic layers. Proven effectiveness (>99% kill rate) against pathogens like Staphylococcus aureus, widely used in surgical and BSL environments.

2. Typical Filter Configuration Strategies

1. Standard 3-Stage Filtration System

1. Customized Solutions by Industry

• Electronics & Semiconductors (ISO 5+)

Objective: Strict control of 0.1–0.3μm particles (≤1000 particles/m³)

Configuration: G4 + F7 prefilters → F9 + carbon molecular filters → U15 terminal HEPA in FFU

Special Requirements: Liquid-sealed ceiling HEPA units; particle counters; differential pressure alerts within ±10% of baseline

• Biopharma (ISO 7–8)

Objective: Microbial control (≤100 CFU/m³ airborne; ≤5 CFU/plate sedimentation)

Configuration: Washable G-grade metal mesh → Antibacterial F8 filters → H14 HEPA with PAO scan ports

Special Requirements: Aerosol challenge tests quarterly; carbon filters replaced upon 30% efficiency drop

• Food & Beverage (ISO 8)

Objective: Prevent cross-contamination by >5μm particulates (≤3.5M/m³)

Configuration: Water-resistant G4 → Stainless steel F7 → H12 terminal with hydrophobic media

Special Requirements: FDA-compliant sealants; filter removal before disinfection; IPA wipe-down

3. Filter Operation & Maintenance Best Practices

1. Installation & Commissioning

• Ensure airtight seals with gel-filled knife-edge frames; apply 3–5mm thick sealants with cross-tightened bolts
• Maintain air velocity within 0.3–0.5m/s (turbulent flow) or 0.36–0.54m/s (laminar flow); velocity deviation <±15%

1. Monitoring & Replacement

• Install differential pressure gauges per unit; terminal resistance should be 1.5–2x initial value
• Predict filter life via smart pressure-time algorithms (accuracy within ±10%)
• Pre-disinfection with UV; personnel in Class A cleanroom garments; hazardous filters packed and labeled for disposal per HW49 regulations

1. Energy Efficiency Optimization

• Use VFD-controlled fans based on filter resistance for 20–30% energy savings
• Implement pressure sensors (±1% FS) with PLC integration
• Adopt nanofiber media for lower resistance and extended life; antimicrobial coatings reduce sterilization frequency by 30%

4. Key Selection Criteria & Troubleshooting Guide

Selection Essentials

• Cleanliness Class: Refer to ISO 14644 particle concentration limits (≥0.1μm)
• Airflow Capacity: Include 20% headroom for filter sizing
• Environmental Compatibility: Hydrophobic filters for high humidity; stainless steel housings for corrosive zones

Common Issues & Fixes

A well-engineered air filtration strategy is critical to maintaining a cleanroom’s performance, balancing cleanliness targets with energy efficiency and ease of maintenance. A three-stage system, enhanced with intelligent monitoring and sustainable materials like nanofiber filters, delivers long-term operational stability while supporting carbon neutrality goals. As industries push toward cleaner, greener operations, high-efficiency, low-resistance filtration will be a defining technology in the next generation of cleanroom innovation.