In pharmaceutical cleanrooms, equipment with exhaust functions (such as biosafety cabinets, fume hoods, instrument washers, tunnel ovens, freeze dryers, etc.) removes indoor air through exhaust. Improper design can easily lead to fluctuations in the room's pressure differential, disrupting the stability of the cleanroom environment.
I. Clarifying Design Principles
The pressure differential control in pharmaceutical cleanrooms must meet GMP and other regulations. When exhaust equipment is installed, the following must be ensured:
1. A dynamic balance between exhaust and makeup air volume (supply air volume = return air volume + exhaust air volume + positive pressure air volume + leakage air volume);
2. The exhaust airflow does not disrupt the cleanroom's unidirectional or turbulent flow, preventing localized eddies and contamination spread;
3. The exhaust system is linked to the room's pressure regulation system for real-time response.
II. Basic Design of the Exhaust System
(I) Independent Exhaust System to Avoid Cross-Contamination
Exhaust equipment (especially equipment handling toxic, reactive, or corrosive substances) must have an independent exhaust system. Sharing with the exhaust or return air systems of other rooms is strictly prohibited to prevent contaminant cross-contamination. For example, the exhaust from a biosafety cabinet must be connected to a dedicated exhaust duct and cannot be combined with regular cleanroom exhaust.
(II) Accurate Calculation and Stable Control of Exhaust Volume
The exhaust volume must be determined based on equipment parameters (such as the rated exhaust volume of the biosafety cabinet), while allowing a 10%-20% margin to account for equipment fluctuations.
Use a constant air volume valve (CAV) to control exhaust volume: Installed at the exhaust equipment outlet or exhaust branch, this mechanical structure automatically maintains a stable exhaust volume, preventing fluctuations in exhaust volume caused by changes in duct resistance (such as filter clogs), which could affect room pressure.
(III) Basic Exhaust Methods:
1. Room intake to room exhaust: This method does not affect the room's air volume balance. The air volume balance formula is: Room supply air volume = Room return/exhaust air volume + positive pressure air volume + leakage air volume. It is important to note that for equipment with high-temperature and high-humidity exhaust gases, such as tunnel ovens and sterilizers, direct discharge into the cleanroom should be avoided.
2. External intake and exhaust: This configuration does not affect the room's air volume balance. The air volume balance formula is: Room supply air volume = Room return/exhaust air volume + positive pressure air volume + leakage air volume.
3. External intake and exhaust: This configuration significantly affects the room's air volume balance. If improperly designed, it can significantly affect the room's pressure differential stability.
Suzhou Pharma Machinery Co.,Ltd.
2025/10/29
Tia
