How should environmental monitoring processes differ for primary engineering controls used in a segregated area versus those located within the cleanroom?

USP Chapter <797> states that environmental monitoring has to be conducted in all environments where sterile compounding occurs, and this holds true for segregated compounding areas. So, even when a compounding aseptic isolator (CAI) is located in a non-ISO classified space, we are still concerned about microbial bioburden produced in and around this engineering control. The challenge for many pharmacists is that while the chapter requires that monitoring occur twice a year, at minimum, it does not delineate action levels for the environment. The chapter simply requires the sampling be done to provide an understanding of what is happening both in and around the device leaving pharmacists wondering as to what standard of cleanliness they should be working toward. I would suggest sampling more often in this scenario so that you can trend your levels and determine if the segregated area is becoming dirtier or cleaner over time. A good place to begin is with the action levels for ISO class 8, which provide a benchmark for air quality to 100 CFUs per cubic meter of air, or 1000 liters.