03-08-2018 11:36 AM
Seeking some guidance on an interesting problem with the hazardous side of our cleanroom setup. We have a non-hazardous possitive ante that branches to the right to our non-hazardous buffer. It is also connected to a small negative hazardous "ante" that then leads to our negative hazardous buffer. All our pressure differentials have been at goal, except this hazardous ante that has been reading -0.04 wc fairly consitently.
I'm assuming the risk of having pressures "above" -0.03 is having too many particles sucked in. As such, am I correct in assuming that this is not something to worry about as long our positive ante differential is at goal and our negative hazardous buffer differential is at goal? My reasoning is that since the positive ante is "working," at worst, all the particles from the positive ante would be sucked into the negative hazardous ante. Since the negative hazardous buffer is at goal, this is then effectively just like having our negative hazardous buffer next to our positive hazardous ante in the worst case scenario. If not, do you recommend sticking to -0.01 to -0.03 as well for the hazardous ante?
I'd appreciate any help I can get on this as I couldn't find anything specific on pressure ranges for hazardous antes per USP 800.
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03-08-2018 12:49 PM
The anteroom needs to be positive pressure and not negative-pressure, when if the HD buffer room is served by a dedicated anteroom. There is NO provision in either USP 797 or 800 for a negative-pressure anteroom.
03-08-2018 02:09 PM
Thanks for the response. Unfortunately, we didn't have much of a say in these designs but I think the intent was to consider the hazardous buffer and the hazardous "ante" as one negative space served by a positive pressure ante. From that perspective, does it at least make sense to keep both of these at the same pressure differential? Or do you absolutely recommend getting the pressures re-adjusted?
03-08-2018 03:47 PM
Based on the limited information I have, treat the negative-pressure anteroom as part of your negative-pressure buffer room. They are the same ISO classification, correct, ISO 7?
03-13-2018 10:49 AM