Air
is of fundamental importance to cleanrooms, either as a contamination source
(microorganisms carried in the air-stream) or as a control measure to minimize
contamination (through the supply of clean air and controlling the direction of
air movement). Therefore, controlling a cleanroom requires careful attention to
the factors of air filtration, air velocity and air flow. While cleanrooms are
typically designed to achieve turbulent airflow, with clean air devices, and EU
/ WHO GMP Grade A / ISO 14644 class 5 areas, the air is designed to be
unidirectional whereby the air direction and air velocity are designed to
remove any contamination deposited into the air-stream away from the critical
area. These devices contain HEPA filters, which control the air-speed and
direction.
In
relation to this topic, Tim Sandle has written a new article:
Poor
airflow uniformity leads to turbulent airflow and vortex formation. In terms of
the velocity of the air, this is described in some regulatory documents: 0,.45
meters per second within arrange of 20%. Whether achieving good airflow (and
thereby avoiding poor airflow) needs to conform to the range specified in
regulatory guidance documents has been a long-standing issue, particularly
given the non-scientific origins of the regulatory guidance values. This
article considers regulatory guidance on airflow velocities and the way that
these are verified, and whether satisfactory airflow can be achieved outside of
these guidance values. The discussion extends to consideration of the
verification of these parameters at working height, especially in light of if
this the most appropriate location by which to measure air velocities.
The
reference is:
Sandle,
T. (2018) Airflow Velocities and Cleanrooms: How fast, how slow, and where to
measure?, Journal of GXP Compliance,
22 (6): 1-10
Posted by Dr. Tim Sandle, Pharmaceutical Microbiology
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Pharmaceutical Microbiology