Calculation Methods for Fresh Air Volume and Supply Air Volume in Dust-Free Clean Rooms
Created on 2024.12.04
Cleanroom Airflow Calculations: Mastering Fresh Air & Supply Air Volume for Optimal Performance
In industries like semiconductor manufacturing, pharmaceuticals, and precision electronics, cleanrooms are vital for maintaining contaminant-free environments. However, their effectiveness hinges on precise airflow control—specifically, fresh air volume (for personnel and pressure) and supply air volume (for particle removal).
This guide breaks down the calculation methods, industry standards, and practical considerations to optimize your cleanroom’s air system.
Why Airflow Control Matters in Cleanrooms
Cleanrooms rely on balanced airflow to:
✔ Maintain ISO-classified cleanliness (e.g., ISO 5 for chip manufacturing)
✔ Ensure worker safety (oxygen supply, CO₂ removal)
✔ Prevent contamination (via positive pressure)
✔ Manage heat & humidity (critical for sensitive processes)
Key Insight: A miscalculation in airflow can lead to failed product batches, regulatory violations, or worker fatigue.
1. Fresh Air Volume: The "Lifeline" of Cleanrooms
A. For Personnel Breathing (OSHA/ASHRAE Standards)
- Formula
:Fresh Air (m³/h)=Number of Workers×30−50 m³/h per personFresh Air (m³/h)=Number of Workers×30−50m³/h per person
- Example
- 20 workers × 40 m³/h =
800 m³/h (minimum requirement).
CO₂ buildup and maintains oxygen levels.
B. For Positive Pressure (ISO 14644 & FDA Guidelines)
- Purpose Prevents unfiltered air infiltration.
- Pressure Differential
- 5-20 Pa
(between cleanroom and adjacent areas).
- Formula
:Leakage Airflow (m³/h)=Room Volume (m³)×Air Changes per Hour (ACH)Leakage Airflow (m³/h)=Room Volume (m³)×Air Changes per Hour (ACH)
C. For Process Exhaust Compensation
- Rule: Fresh air ≥ exhaust air to avoid negative pressure.
- Example: If exhaust = 500 m³/h, fresh air must be ≥500 m³/h.
2. Supply Air Volume: The "Engine" of Cleanliness
A. Based on Air Change Rates (ISO 14644 Standards)
Cleanroom Class | Air Changes/Hour (ACH) | Typical Use Cases |
ISO 5 (Class 100) | 500-600 | Semiconductor lithography |
ISO 7 (Class 10,000) | 25-35 | Pharmaceutical filling |
ISO 8 (Class 100,000) | 15-20 | Electronics assembly |
Example Calculation:
- Room: 10m × 8m × 3m = 240 m³.
- Class 100K @ 18 ACH → 240 × 18 = 4,320 m³/h.
B. Unidirectional Flow Cleanrooms (Critical for Chip Fabs)
- Vertical Flow: 0.3–0.5 m/s (e.g., lithography zones).
- Horizontal Flow: 0.2–0.4 m/s (e.g., packaging areas).
- Formula:Supply Air (m³/h)=Wind Speed (m/s)×Cross-Sectional Area (m²)×3600Supply Air (m³/h)=Wind Speed (m/s)×Cross-Sectional Area (m²)×3600
Example:
C. Cooling Airflow for Equipment (Data Centers, Laser Labs)
- Rule of Thumb: 300–400 m³/h per kW of heat dissipation.
- Example: 10 server cabinets @ 3 kW each → 30 kW × 350 m³/h = 10,500 m³/h.
3. Dynamic Adjustments & Real-World Challenges
- Aging Cleanrooms: Duct leaks can increase fresh air demand by 10–20%.
- Process Upgrades: New equipment may require higher ACH rates.
- Energy Efficiency: Variable Air Volume (VAV) systems can cut costs by 25%.
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