I work for a medical device company and we set up an ISO 7/8 cleanroom. I set up an environmental monitoring procedure that includes quarterly monitoring of our particulate, as well as viable microorganisms for air and surfaces. We now have several sessions-worth of data, and I now need to establish alert and action levels. I’m not familiar with how to decide these levels, however.

Are there any industry norms or statistical techniques for setting up initial levels? If we claim, ISO 7 at rest and ISO 8 in operation, do we need to establish levels for each state?

I’m not an expert in this area, but viable and particulate data in “at rest” situations may not be very persuasive to government monitoring agencies or to customers who audit. Far more compelling are the “in operation” data which reflect what the devices are seeing during normal operating conditions.

Regards

Howard

Jozaeta, sorry for the very long delay in responding to your inquiry, but I recently came across some information that might be of use.
At the 2004 Cleanrooms East Conference in Orlando, a paper on “Establishing and Environmental Monitoring Program” was presented. In that paper viable guidelines for ISO Class 7 & 8 cleanrooms were given along with information showing that in these “dirtier” environments, the CFU histogram shows a normal distribution (i.e. Gaussian) with suggested alert levels of mean + 1.65*std deviation and action levels of mean + 2.33*std deviation. You may wish to contact Cleanrooms Magazine to obtain a copy of this presentation.
See also the NSF publication “Environmental Monitoring” available at http://www.cerhb.ufl.edu/pdf/edcenter/environmental_monitoring.pdf/
Action and alert levels for ISO Class 7 & 8 environments are presented on page 25 of this document.
You may wish to consult the book by Lucia Clontz, “Microbial Limit and Bioburden Tests: Validation Approaches and Environmental Limits” 2nd ed. Taylor and Francis Group, 2009 for information on this topic.
Finally you may wish to review Chapter of the US-American Pharmacopoeia (USP), “Microbiological Evaluation of Clean Rooms and Other Controlled Environments” for guidance on action and alert levels.
I apologize for the lengthy response, but hopefully this will get you started.
Howard Siegerman, Ph.D.
CRF Technical Moderator

Hi Howard:
Thank you very much for the references. It looks like they will point me in the right direction.

- Jason