In the pharmaceutical industry, HVAC systems within clean areas must not be arbitrarily or completely shut down. Provided that thorough validation has been conducted-adhering to the core principles of quality risk management and supported by strict Standard Operating Procedures-a "standby mode" involving reduced-frequency operation may be adopted during non-working hours. The fundamental objective of this approach is to ensure that the clean environment remains free from contamination.
Although GMP guidelines do not explicitly mandate specific protocols for switching HVAC systems on or off, they unequivocally establish validation, as well as the mitigation of contamination and cross-contamination risks, as fundamental principles. Specifically, for sterile drug manufacturing facilities, the use of a standby mode during nighttime hours is generally discouraged. In instances of prolonged production shutdowns, the decision to activate standby mode or to completely shut down the HVAC system may be made at the facility's discretion, based on the anticipated duration of the shutdown; however, necessary re-validation procedures must be completed prior to resuming normal operational mode. Regardless of the operational mode, the system must consistently maintain a differential pressure of ≥10 Pascals between clean and non-clean areas, while also satisfying basic requirements regarding temperature and humidity.
If a standby mode is to be implemented, comprehensive validation must first be completed, and a corresponding SOP must be established. This validation process must encompass the following aspects: verification under "worst-case" conditions corresponding to the maximum permissible duration of standby operation; verification of differential pressure control to ensure a pressure difference of ≥10 Pa (with appropriate pressure gradients) while operating at reduced frequency; verification that particulate and microbiological cleanliness standards are met even at reduced air exchange rates; verification of the "self-purification" recovery time required after switching back to full production mode; verification that the transition process is smooth and controllable; and verification of system performance under the distinct operating conditions characteristic of both summer and winter seasons.
The primary risks associated with standby mode include the failure to maintain adequate differential pressure-which could result in the backflow of lower-grade air into higher-grade clean areas-and insufficient air supply volume or air exchange rates, which could compromise particulate cleanliness standards. Consequently, priority must be placed on safeguarding three critical factors: maintaining a positive differential pressure to prevent air backflow; ensuring that particulate levels within the room remain within acceptable limits under static conditions; and guaranteeing the stability of differential pressure through a continuous monitoring system. Should any anomalies be detected, the affected area must undergo immediate re-cleaning and disinfection procedures.
Suzhou Pharma Machinery Co.,Ltd.
2026/05/04
Icey
