How to Design AHUs for Cleanroom Applications ?

Introduction

Cleanrooms are specialized environments where air quality, temperature, and humidity must be strictly controlled to meet industry standards. The Air Handling Unit (AHU) plays a critical role in ensuring contamination control, energy efficiency, and regulatory compliance. Whether in pharmaceuticals, electronics, biotechnology, or healthcare, the design of a Cleanroom AHU must be meticulously planned to maintain precise environmental conditions.

In this blog, we’ll explore:

  • Key design considerations for Cleanroom AHUs
  • Components and configurations
  • Filtration strategies and airflow management
  • Energy efficiency and sustainability practices
  • Maintenance best practices

1. Key Design Considerations for Cleanroom AHUs

The design of a Cleanroom AHU must align with ISO 14644 standards and industry-specific regulations (such as GMP, FDA, and EU Annex 1). Here are the critical design factors:

1.1 Air Quality & Filtration Efficiency

  • Cleanroom AHUs must maintain specific ISO classification levels (e.g., ISO 5, ISO 7, ISO 8).
  • High-efficiency particulate air (HEPA) or ultra-low penetration air (ULPA) filters are required to remove airborne contaminants.
  • Multi-stage filtration (Pre-filters → Medium Filters → HEPA/ULPA) ensures optimal air cleanliness.

1.2 Temperature and Humidity Control

  • Precision temperature control (+/- 1°C) is required for sensitive manufacturing processes.
  • Relative humidity (RH) control (ranging from 40%-60%) prevents electrostatic discharge and microbial growth.
  • Dehumidification and humidification systems integrated into AHUs regulate moisture levels.

1.3 Airflow Management

  • Laminar airflow (unidirectional flow) is critical for high-class cleanrooms (ISO 5 and below).
  • Turbulent airflow is acceptable for lower-class cleanrooms (ISO 7-8).
  • Air Changes per Hour (ACH) (Use TheHVACLab ACH Calculator) varies based on the classification:
    • ISO 5: 240-600 ACH
    • ISO 7: 60-90 ACH
    • ISO 8: 20-40 ACH

1.4 Pressure Differentials

  • Positive pressure (+10 to +15 Pa) prevents contaminants from entering cleanrooms.
  • Negative pressure (-10 to -30 Pa) is required in biohazard labs and pharmaceutical containment zones.
  • Airlocks and pressure monitoring sensors ensure proper differential pressure.

1.5 Regulatory Compliance

  • Compliance with ISO 14644, FDA, GMP, and EU Annex 1 guidelines is mandatory.
  • Cleanroom AHUs must meet ASHRAE 170 standards for healthcare environments.

2. Cleanroom AHU Components & Configurations

A well-designed Cleanroom AHU consists of several essential components:

2.1 Filtration System

  • Pre-filters: Captures large dust particles and extends the life of HEPA filters.
  • Bag/Medium Filters: Removes smaller particulates before HEPA filtration.
  • HEPA/ULPA Filters: Final filtration to maintain cleanroom classification.
  • Carbon Filters (Optional): Controls odors and VOCs in specialized applications.

2.2 Fan & Motor System

  • EC (Electronically Commutated) Fans: Improve efficiency and reduce energy consumption.
  • VFD (Variable Frequency Drive): Adjusts airflow based on cleanroom occupancy and load.
  • Redundant Fan Systems: Ensures continuous operation in critical applications.

2.3 Temperature & Humidity Control

  • Cooling Coils: Chilled water or DX coils for temperature regulation.
  • Heating Coils: Steam, electric, or hot water coils for precise temperature control.
  • Humidifiers & Dehumidifiers: Ultrasonic or steam-based humidifiers for RH management.

2.4 Airflow Control & Distribution

  • Dampers & Louvers: Modulate air distribution and maintain airflow balance.
  • Plenum Chambers: Optimize airflow uniformity for laminar flow applications.
  • Ductwork Design: Should be smooth and sealed to prevent particle accumulation.

3. Filtration Strategies & Airflow Design

A multi-stage filtration strategy is essential to achieve contamination-free air in cleanrooms.

3.1 Multi-Stage Filtration Approach

Filter TypeEfficiencyParticle Size
Pre-FiltersG4 – MERV 8-1010-20 μm
Secondary FiltersF7/F9 – MERV 13-161-10 μm
HEPA/ULPA FiltersH13-U17 – MERV 17-200.3 μm
Carbon Filters (Optional)VOC AbsorptionChemical Fumes

3.2 Airflow Distribution Techniques

  • Laminar Flow Ceilings: Provide uniform downward airflow in critical areas.
  • Turbulent Flow for Lower Class Cleanrooms: Ensures efficient mixing of clean air.
  • Ceiling & Floor Return Air Grilles: Optimized placement reduces particle buildup.

4. Energy Efficiency & Sustainability in Cleanroom AHUs

Designing an energy-efficient Cleanroom AHU lowers operational costs while maintaining high-performance standards.

  • EC Fans & VFDs: Optimize fan speed and power consumption.
  • Heat Recovery Wheels: Reclaim energy from exhaust air.
  • Advanced Controls & IoT Sensors: Monitor real-time conditions and optimize settings.
  • Demand-Based Ventilation: Adjust airflow based on occupancy levels.
  • High-Efficiency HEPA Filters: Reduce pressure drop and energy use.

Call-To-Action (CTA)

  • Need expert Cleanroom AHU design? Contact us today for a free consultation!
  • Stay updated with the latest HVAC trends—subscribe to The HVAC Lab newsletter!

For more insights on HVAC system design and cleanroom technology, stay connected with The HVAC Lab!

Scroll to Top