Also: the ACH is really for the benefit of the human occupants; not necessarily the pharmaceuticals being processed; and a consevative ASHRAE guideline is 6 ACH.
What you ought to be looking at is the filtration efficiency in microns and comparing that to the pharmaceutical manufacturer's limits on contamination. Is just one pharmaceutical being processed or many of different types? Cross-contamination could be an issue in the case of many products being processed simultaneously; whereas if jus one is being processed, it might be a moot point.
