Differential pressures of clean rooms

Dear all,

iam maintaining the difference of same garde is 5pa and different grades diffrence of DP is 15pa.

What is the limit of same grade and different garde?

as per ISO 14644

There is no recommended limit for same grade in any of the guidances that I’ve discovered. There is only a limit between different grades (which you have referenced). In practice, many of the companies I work with do extra due dilligence and have a pressure difference between areas of the same grade, between areas. For example a wash room might be ISO 7 and a corridor ISO 7. But the washroom will be a lower pressure than the corridor since there are often contaminants in the washroom.

Dear Jaredcroft,

one auditor told with me, same grade clean room limit is >0.5mm o f wc.

which guidelines are showing the above limit. please tell me.

World Health Organization, and Eudralux both recommend 15 Pa for areas of different cleanliness. That is all they state. In fact they only state that this is “common” and “recommended”. There are other place which state that is needs to be in the correct direction but don’t give a required value. So I haven’t seen a regulation which “requires” anything for areas of the same cleanliness level.

Dear Jaredcroft,

please tell me about Pharma clean rooms RH%?

Any guidelines are showing the limit of RH%?

Controlled area (Like grade-C &D)

Aseptic area (Like Grade-B & A)



There is no requirement for humidity.

General guidance is to maintain humidity levels between 35% and 60% RH. Higher humidity supports microbial growth, while too little humidity causes problems with static; either extreme can affect worker comfort and the ability to work effectively.