“We recommend that measurements to confirm air cleanliness in critical areas be taken at sites where there is most potential risk to the exposed sterilized product, containers, and closures. The particle count- ing probe should be placed in an orientation dem- onstrated to obtain a meaningful sample. Regular monitoring should be performed during each pro- duction shift. We recommend conducting nonviable particle monitoring with a remote counting system. These systems are capable of collecting more com- prehensive data and are generally less invasive than portable particle counters. See Section X.E. for addi- tional guidance on particle monitoring. “