Core Equipment in Cleanroom HVAC Systems

A cleanroom HVAC system is usually built around several key equipment modules: fresh air pretreatment, MAU, recirculation air handling, terminal filtration, dehumidification, cooling and heating sources, ductwork, pressure control, and monitoring systems.

1. Make-Up Air Unit MAU: The Core Unit for Cleanrooms

The Make-Up Air Unit, or MAU, handles 100% outdoor air before sending it into the clean area. It is responsible for temperature control, humidity control, filtration, dehumidification, and pressure support.

A typical MAU may include the following sections:

1. 1. G4 primary filter: Blocks large dust, willow catkins, and coarse particles to protect downstream coils.
2. 2. Pre-cooling coil: Uses chilled water for summer cooling and dehumidification.
3. 3. Primary heating section: Uses hot water or electric heating for winter heating and dew point adjustment.
4. 4. Rotary deep dehumidification section: Required for lithium battery workshops. Silica gel or molecular sieve rotors, with 110–130°C regeneration heating, can reduce fresh air to an ultra-low dew point of -40°C to -60°C.
5. 5. Secondary heating section: Provides precise temperature compensation for constant temperature control.
6. 6. Humidification section: Pharmaceutical and precision electronic cleanrooms often use dry steam isothermal humidification. Ordinary plants may use wet-film humidification with reheating compensation in winter.
7. 7. F8/F9 medium filter: Captures medium particles and protects terminal HEPA filters.
8. 8. Variable-frequency supply fan: Maintains cleanroom positive pressure and adjusts airflow according to pressure demand.
9. 9. H10–H12 sub-HEPA filter: Provides primary clean air filtration at the MAU outlet and reduces the load on FFU systems.

Supporting components may include regeneration fans, heat recovery coils, condensate drainage, airtight dampers, motorized shut-off dampers, and variable air volume dampers.

2. Recirculation Air Handling Unit RCU / AHU

The RCU or AHU mainly handles recirculated indoor air. It does not process outdoor fresh air directly.

Common configurations include primary and medium filters, chilled or hot water coils, recirculation fans, and in some pharmaceutical cleanrooms, ozone or UV disinfection sections.

The main function is to balance indoor cooling and heating loads, stabilize room temperature, and work with the MAU to control humidity.

3. Terminal Clean Air Equipment

Terminal filtration equipment directly affects the cleanroom cleanliness level.

1. 1. FFU fan filter unit: Standard equipment for ISO Class 8, ISO Class 7, ISO Class 6, and higher-grade cleanrooms. It integrates a fan with HEPA or ULPA filters such as H13 or H14.
2. 2. Laminar flow hood: Used for local high-cleanliness areas such as filling, coating, dispensing, and injection processes.
3. 3. Clean bench: Provides a localized ultra-clean operating area, including biological safety cabinets and dust-free workstations.
4. 4. HEPA terminal air outlet: Used in ducted turbulent-flow cleanrooms with HEPA filters installed at the supply air terminal.
5. 5. Air shower and cargo shower: Removes dust from personnel and materials, blocks dirty outdoor air, and helps maintain pressure difference through interlocked doors.

4. Dedicated Dehumidification Equipment for Lithium Battery Dry Rooms

Ultra-low dew point dehumidification is mainly required in lithium battery dry rooms. Ordinary cleanrooms usually do not need this configuration.

1. 1. Molecular sieve deep dehumidification rotor unit: The core equipment for achieving dew points below -40°C. It may include fresh air rotors and indoor recirculation rotors.
2. 2. Regeneration electric or steam heater: Removes moisture from the rotor and maintains dehumidification capacity.
3. 3. Nitrogen or compressed air pre-dryer: Keeps process gas dew point at ≤ -70°C to prevent moisture from damaging battery cells.

5. Cooling and Heating Source Systems

The cooling and heating source system provides energy for MAU, RCU, AHU, and other cleanroom air conditioning equipment.

1. 1. Chiller: Centrifugal or screw chillers usually provide 7°C chilled water for cooling and dehumidification coils.
2. 2. Plate heat exchanger: Separates the primary chilled water system from the secondary cleanroom low-temperature water system.
3. 3. Hot water or steam boiler: Provides heat for winter heating, rotor regeneration, and steam humidification.
4. 4. Cooling water pump, chilled water pump, and cooling tower: Required for water-cooled systems to remove condenser heat.
5. 5. Headers, expansion tanks, and water treatment devices: Stabilize system pressure and help prevent coil scaling or blockage.

6. Ductwork, Pressure Control, and Auxiliary Equipment

Cleanroom HVAC systems also require reliable ductwork, valves, filters, exhaust, and drainage systems.

1. 1. Filters: G4 primary filters, F8 medium filters, H13/H14 HEPA filters, and ULPA filters should be monitored and replaced based on pressure difference.
2. 2. Steam humidification system: Includes dry steam humidifiers, steam-water separators, and pressure reducing valves.
3. 3. Condensate drainage system: Includes condensate pipes, traps, and collection tanks to prevent water accumulation and microbial growth.
4. 4. Exhaust system: Includes process exhaust cabinets, variable-frequency exhaust fans, activated carbon adsorption boxes, fire dampers, and solvent exhaust treatment.
5. 5. Airtight dampers: Motorized shut-off dampers, airflow regulating dampers, and check dampers help prevent humid air backflow.

7. Automation and Monitoring Systems

Cleanroom HVAC must be supported by accurate monitoring and automatic control systems.

1. 1. Temperature and humidity transmitters
2. 2. Ultra-low dew point transmitters for lithium battery dry rooms
3. 3. Indoor differential pressure sensors for clean areas, corridors, and outdoor reference points
4. 4. Filter differential pressure gauges and switches for clogging alarms
5. 5. Particle counters and airborne bacteria samplers for pharmaceutical GMP cleanrooms

Typical System Configurations

Ordinary Electronic Cleanroom

A standard electronic cleanroom without ultra-low dew point requirements usually includes chillers, cooling towers, MAU fresh air units, RCU recirculation units, FFU or HEPA air outlets, air showers, steam humidification, and automatic control systems.

Lithium Battery Dry Room

A lithium battery dry room focuses on dew point control. The typical system includes chillers, MAU with deep dehumidification rotors, recirculation dehumidification units, FFU, laminar flow hoods, regeneration heating systems, process gas dryers, and online dew point monitoring.

Pharmaceutical GMP Cleanroom

A pharmaceutical GMP cleanroom usually requires MAU steam isothermal humidification, disinfection sections, high-efficiency filtration, airborne bacteria monitoring, sealed exhaust, and pressure control between clean zones.

Conclusion

The core equipment of a cleanroom HVAC system depends on the process requirements. Ordinary cleanrooms focus on temperature, humidity, filtration, and pressure control, while lithium battery dry rooms require ultra-low dew point dehumidification. Pharmaceutical GMP cleanrooms require stronger microbial control, disinfection, and pressure zoning.