Monday 8 June 2020

Best practices for airflow visualization

Air is of fundamental importance to cleanrooms and clean air devices, either as a contamination source (microorganisms carried in the airstream) or as a control measure to minimise contamination (through the supply of clean air). Therefore, controlling a cleanroom requires careful attention to air filtration and airflow.

Assessing airflow is undertaken through airflow visualisation studies (or what are colloquially termed ‘smoke studies’). The purpose of flow visualisation is to confirm the smoothness, flow patterns and other spatial and temporal characteristics of airflow in an installation.

For this, the airflow is examined through airflow visualisation mapping whereby smoke is generated, and the behaviour of the smoke is studied and then captured by a video camera.

Air flow visualisation is one of the less clear-cut activities required of aseptic manufacturers. Regulations refer to such studies, yet little in the way of guidance is provided. However, judging by warning letters and other regulatory trends, many industries are running behind in terms of compliance expectations. The regulator findings suggest that evaluation, presentation and demonstration of airflow is not well understood. In this article, we will discuss the main regulatory findings, as evidenced from recent USA Food and Drug Administration (FDA) 483s and assess these for the main areas for concern and offer best practices for addressing the regulatory observations.

In relation to this topic, a new article of interest has been published in GMP Review. The reference is:

Saghee, M. R., Sandle, T., and Das, P. (2019) Regulatory inspections of sterile facilities – the focal points Part 2: Airflow visualisation, GMP Review, 18 (3): 15-21

For further details, please contact Tim Sandle.

Posted by Dr. Tim Sandle, Pharmaceutical Microbiology Resources (

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