Calculation Formula for the Quantity Requirement of FFU in Class 1000 Cleanrooms
Created on 2024.12.16
Why Proper FFU Configuration Matters
Fan Filter Units (FFUs) are the heart of cleanroom air purification, directly impacting:
✔ Particle control (meeting ISO 14644-1 Class 6 / Fed Std 209E Class 1000)
✔ Airflow uniformity (preventing dead zones)
✔ Energy efficiency (balancing ACH and operational costs)
At Guangzhou Cleanroom Construction Co., Ltd., we specialize in ISO-certified cleanroom solutions. This guide provides a step-by-step FFU calculation method for Class 1000 cleanrooms, including real-world examples and key design considerations.
1. Class 1000 Cleanroom Standards
Parameter | Requirement | Industry Standard |
Particle Count | ≤1,000 particles/ft³ (≥0.5µm) | ISO 14644-1 Class 6 |
Temperature | 22 ± 2°C | FDA, EU GMP Annex 1 |
Humidity | 50 ± 5% RH | IEST-RP-CC012 |
Air Changes | 50–60 ACH | WHO TRS 961 (Annex 5) |
Pressure | +10 to +15 Pa | NSF/ANSI 49 |
Key Insight: FFUs must provide ≥99.99% filtration at 0.3µm (HEPA H14/ULPA U15).
2. FFU Quantity Calculation Formula
Step 1: Calculate Cleanroom VolumeV (m3)=Length×Width×HeightV(m3)=Length×Width×Height
Example:
- Room: 20m (L) × 10m (W) × 2.8m (H)
- Volume = 560 m³
Step 2: Determine Total Airflow RequirementQ (m3/h)=V×Air Change Rate (ACH)Q(m3/h)=V×Air Change Rate (ACH)
Example:
- ACH = 55
- Total Airflow = 560 × 55 = 30,800 m³/h
Step 3: Select FFU Model & Calculate Quantityn=QSingle FFU Airflow (q)n=Single FFU Airflow (q)Q
Example:
- FFU airflow (q) = 1,000 m³/h
- FFUs Needed = 30,800 ÷ 1,000 = 30.8 → Round up to 31
Pro Tip: Add 10–20% margin (e.g., 35 FFUs) for:
- Filter loading over time
- Future process upgrades
3. Critical Design Factors
A. FFU Layout Optimization
- Grid Pattern: Space FFUs evenly (e.g., 1 FFU per 4–6 m²)
- Avoid Short-Circuiting: Use perforated floor tiles for vertical unidirectional flow
- Local Protection: Increase FFU density over high-risk areas (e.g., filling lines)
B. Energy Efficiency Considerations
Strategy | Energy Savings |
EC Motor FFUs | 30–50% vs. AC |
Variable Air Volume | 20–35% |
Demand-Based Control | 15–25% |
Case Study: A 500 m² Class 1000 cleanroom saved $12,000/year by switching to VFD-controlled FFUs.
4. Maintenance & Compliance
FFU Service Checklist
- Monthly: Check airflow velocity (≥0.45 m/s)
- Quarterly: HEPA filter integrity test (DOP/PAO)
- Annually: Motor bearing lubrication
Regulatory Notes:
- ISO 14644-2: Requires particle count tests every 6–12 months
- FDA 21 CFR 210/211: Mandates filter replacement records
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