The number of personnel allowed inside a cleanroom cannot be set arbitrarily. It is governed by mandatory regulatory requirements and supported by scientific principles. Three separate calculation methods must be applied, with the minimum result taken as the occupancy ceiling. Staff occupancy directly impacts the risk of microbial contamination to products and is a core audit item during GMP inspections and routine cleanliness monitoring.
1. Three Calculation Methods for Maximum Occupancy, adopt the smallest figure as the official occupancy limit:
(1).Fresh Air Volume Calculation
Formula: Allowable Occupancy = (Total room supply air volume (m³/h)*Fresh Air Ratio (%)) /40
(2). Airborne Viable Count Calculation
Formula: Allowable Occupancy = (Airborne viable particle limit (CFU/m³)*Room Volume (m³)*Air Changes per Hour (ACH)) /42,000
(3). Per Capita Operating Area Calculation
Formula: Allowable Occupancy = Net usable room area (m², after deducting equipment, tooling and fixed walkways)/Minimum floor space allocated per person
The official maximum occupancy for the room equals the minimum value derived from the fresh air, airborne viable particle and floor area calculations.
2. Graded Occupancy Control by Cleanroom Classification
(1). Grade A laminar flow aseptic zones: Restrict to a maximum of 1–2 persons. Unnecessary movement is prohibited; only essential critical operations are permitted.
(2). Grade B background clean zones: Cap normal occupancy at 4–6 persons. Regulations mandate full-load aseptic process simulation validation before production launch.
(3). Grade C & D general production clean zones: Strictly adhere to the calculated occupancy ceiling. Continuous real-time monitoring of particles and microbes is required to sustain compliance.
3. Common Pitfalls to Avoid in Daily Management
(1). Only calculating based on floor area while ignoring the two mandatory checks of fresh air volume and microbial load, leading to an overestimated occupancy limit.
(2). Rounding up fractional calculation results; the correct practice is truncating decimals to lower the occupancy cap.
(3). Summing the maximum allowable personnel of individual rooms directly as the total workshop occupancy, without cross-verifying against the overall fresh air supply capacity of the central HVAC system.
(4). Commencing production in Grade B aseptic areas after only theoretical paper calculations, without completing mandatory aseptic process simulation validation.
(5). Failing to recalculate room occupancy limits following workshop layout renovations or major HVAC overhauls.
Suzhou Pharma Machinery Co.,Ltd.
2026/07/24
Icey
