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Pharmaceuticals/Air Movement after HEPA Filteration


Dear Michael, We appreciate your great contribution to the mankind and Industry.

One of my colleagues has told us that air flow become wavy as they passed after HEPA filters. He is of the opinion that the air flow become wavy due to the HEPA construction (folding)and therefore air make the same pattern after coming out of the HEPA filters. This might look funny quation to you but I appreciate if you can help us to make better understanding.

Thanks in advance


Dear Irfan:

Your flattery, while appreciated; "contribution to mankind" is a little exaggerated.

Anyway, in answer to your question. HEPA filters are used to remove particulate contamination from the incoming air to a clean work area; however inside the clean working area activities happen that generate particles, especially when people are working in the area.

To remove these in-situ generated particles we need to sweep them away - this is done by having post-HEPA filter laminar airflow. The get laminarity we need velocity (a minimum of 90ft/second) in the air flow.

"Wavy" air (technically called turbulent air flow) does nothing to remove the in-situ particulates. The "waviness" has nothing to do with the HEPA material or to folds in its construction.

I hope this helps.


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Michael Anisfeld


Disclaimer: SORRY BUT I DO NOT ANSWER QUESTIONS RELATED TO: DRUG ACTIONS/INTERACTIONS, INTERNET DRUG PURCHASES, RESULTS OF DRUG TESTS, IDENTIFYING DRUGS (FOR WHICH YOUR LOCAL PHARMACIST IS THE BEST PERSON TO CONSULT). My expertise is answering questions relating to pharmaceutical manufacturing and quality technologies, drug regulations and specifically GMP requirements


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