✅ Air Handling Unit (AHU) Components for Class D

 

✅ Air Handling Unit (AHU) Components for Class D

Component	Purpose / Function
1. Pre-filters (EU4 / G4 class)	Remove large dust particles (≥10 µm); installed at return air or fresh air intake
2. Fine filters (EU7 / F7 class)	Remove medium-sized particles (≥1–5 µm); ensure secondary filtration before HEPA
3. HEPA Filters (EU13 or H13)	Final stage filtration; ≥99.97% efficient at 0.3 µm; placed in terminal boxes inside room
4. Blower/Fan Section	Ensures required airflow and pressure; may be belt-driven or direct-driven
5. Cooling Coil (Chilled Water or DX)	Controls temperature (18–25°C); removes heat load from supply air
6. Heating Coil (Electric/Hot Water)	Optional – used to maintain temperature in colder conditions
7. Humidifier / Dehumidifier	Controls RH (typically 45–60%); often integrated via chilled coil or separate system
8. Fresh Air Damper	Controls intake of fresh air; supports positive pressure and dilution ventilation
9. Return Air Damper	Balances air pressure and facilitates recirculation of treated air
10. Mixing Box	Mixes fresh air and return air to achieve desired air quality and conditioning
11. Motorized Control Dampers	Automated control of airflow based on differential pressure or occupancy
12. Vibration Isolators	Prevent vibration transmission to ducts or cleanroom
13. Terminal HEPA Filter Housing	Final air delivery component; ensures filtered air enters the cleanroom
14. Differential Pressure Gauges / Magnehelic Gauges	Monitor pressure drop across filters (pre-filters and HEPA)

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🎯 Design Considerations for Class D:

• Air Changes per Hour (ACPH): ≥10–15 ACPH

• Positive Pressure: 10–15 Pa against adjacent uncontrolled areas

• HEPA Filters: Required at terminal supply

• Filtration Efficiency: Minimum 2-stage filtration (pre + fine) before HEPA

• No Unfiltered Air: All supply air must be HEPA-filtered