I have to perform operational qualification for an unidirectional airflow device (formerly referred as laminar work bench). Within our organization, some controversial exist.
Some people said the airflow velocity must be measured at working position AND 6 inches from the filter face. The guidance value (0.36 ~ 0.45 m/s) must be maintained at the working position, not filter face. The data from the filter face is just for informational purpose. In my humble guess, if the guidance velocity is achieved at the working position the velocity from 6 inches from the filter face will be much higher, which will create negative impact on the airflow pattern at the working position due to high supplying air velocity. But not sure. Eventually airflow pattern test will tell me the everything for this approach. Also there is a chance that high face velocity will result in the leaks in HEPA filter media and frame.
But others believe that the guidance value must be maintained at 6 inches away from the filter face. This is historically used for many years in the pharmaceutical industry. But in order to comply GMP, the velocity data at the working position is also important. As you know the measurement of the velocity at the working position would be highly variable due to the equipment size and configuration within the unidirectional airflow device. Proper airflow pattern at the working position is more important than achieving the specified airflow velocity at the working position. So velocity measurement at the working position will be information purpose but can be helpful in understanding the observed airflow pattern.
I’m very frustrated which approach is right interpretation. Especially, this plant should comply EU GMP, rather than US FDA. EU GMP Annex 1 states that “Laminar air flow systems should provide a homogeneous air speed in a range of 0.36 ~ 0.54 m/s (guidance value) at the working position in open clean room applications”. For EU GMP compliance, the former interpretation will be correct. But practical and historic point of view, the latter interpretation will be correct.
Does anyone have the experience on this case for complying EU GMP? Also I’d like to listen the current industry interpretation (practice) for US FDA compliance.
Thanks in advance.