Pressure Differential / Positive Pressure

Details

A pressure differential is the difference in air pressure between adjacent areas of different grade, and positive pressure is the state in which a cleanroom is held above its surroundings so that filtered air flows only outward. EU GMP Annex 1 §4.14 requires cleanrooms to maintain a positive pressure or airflow relative to a lower grade background under all operational conditions so that the area is effectively flushed, with a guidance value of a minimum 10 Pa between adjacent rooms of different grade and particular attention to protecting critical zones; 21 CFR 211.42(c)(10)(iii) requires aseptic processing areas to be supplied with HEPA filtered air under positive pressure, whether or not laminar flow is used. Containment areas handling highly active substances or pathogens use negative pressure instead, so what matters is not the direction itself but whether the designed direction is always maintained and monitored. Inspections cite pressure differentials not continuously monitored or recorded, work carried out with the differential at zero or reversed and no alarm, doors opened together so the cascade collapses, and pressure excursions not carried into a product impact assessment.

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Real inspection findings

Findings from regulators' inspection documents in which this term appears.

1. Your firm failed to document and measure pressure differentials during operations to demonstrate proper airflow.

   FDA · FDA Warning Letter · 2021-04-27

2. Your firm produced sterile drug products within the REDACTED (b)(4) Clean Room during pressure differential failures on 5/25/16, 5/26/16, 5/27/16, 5/31/16,6/8/16 and 6/9/16.

   FDA · FDA 483 · 2024-01-17

3. Room air pressure differentials are not monitored during each production ofaseptically processed sterile drug products.

   FDA · FDA 483 · 2024-01-17