Tool 7: Cleanrooms & Operation Theatres
Cleanroom Airflow Rate (ACPH) & Modular HEPA Sizing
Calculates total circulating airflow for ISO Class 5–8 cleanrooms and NABH hospital modular operation theatres. Sizes modular H14 HEPA units using physically coherent manufacturer airflow ratings.
✔ 1. Formula Verified
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⚡ 2. Engineering Screening
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📐 3. Guidelines Referenced (ISPE / NABH)
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⚖ 4. Engineer Review Required
Cleanroom Geometry & Classification
Feet
Feet
Feet
Design Guidelines
Manufacturer Rating
Physically verified: a 2ft × 2ft (4 ft²) face at 90 FPM laminar face velocity delivers exactly 360 CFM.
Cleanroom Airflow Sheet
ISPE / NABH Model
H14 Terminal HEPA Filter Units Required
6 Units
Basis: 360 CFM per 2ft × 2ft module at 90 FPM
Total Circulating Airflow
2,000 CFM
Net Cleanroom Volume
4,000 cu.ft
Design Air Change Rate
30 ACPH
Fresh Air (Positive Pressure)
400 CFM
Governing Standards & HEPA Sizing Methodology
Standards & Cleanroom Guidelines
- ISO 14644-1: 2015 Scope: Classifies cleanrooms solely by maximum permissible airborne particle concentrations per cubic meter (≥ 0.1, 0.2, 0.3, 0.5, 1.0, 5.0 μm). ISO 14644-1 does NOT mandate ACPH values.
- ACPH Design Guidelines: Derived from recognized industry engineering guidelines:
- ISPE Baseline Guide Volume 2: Oral Solid Dosage Forms.
- FDA cGMP Guidance: Sterile Drug Products by Aseptic Processing.
- NABH Guidelines: Air Conditioning in Operation Theatres (30–60 ACPH for Super-Specialty OTs).
Physical Airflow & Filter Sizing
To maintain laminar non-aspirating flow, face velocity across cleanroom ceiling filters is typically maintained at 90 FPM ± 20% (0.45 m/s ± 0.1 m/s):
Airflow per 2ft × 2ft module = 4 ft² × 90 FPM = 360 CFM
Total_CFM = (Room_Volume_cuft × ACPH) / 60
N_HEPA = ⌈ Total_CFM / Q_HEPA,rated ⌉
Fresh_Air = max(Total_CFM × 0.20, Room_Volume × 6.0 / 60)
Total_CFM = (Room_Volume_cuft × ACPH) / 60
N_HEPA = ⌈ Total_CFM / Q_HEPA,rated ⌉
Fresh_Air = max(Total_CFM × 0.20, Room_Volume × 6.0 / 60)
⚖ Statutory Notice & Engineering Disclaimer (Tier D Integration)
This calculation provides preliminary engineering screening. Final cleanroom design requires particle challenge testing (DOP/PAO filter integrity testing), recovery time validation, pressure cascade balancing (e.g. 15 Pa positive gradient), and qualification (DQ, IQ, OQ, PQ) verified by a certified cleanroom validation engineer.