To evaluate different microbial air samplers it is useful to read what is written in the USP 38 of the US Pharmacopeial – official from May 1, 2015:
“There are no standard methods for air sampling, and available literature indicates that air sampling methods are highly variable.
It should not be assumed that similar sample volumes taken by different methods will produce similar rates of recovery.
Many factors can affect microbial recovery and survival, and different air sampler suppliers may have designed their systems to meet different requirements.
Also, sample-to-sample variations in microbial sampling can be extensive. Limited data are available regarding the accuracy, precision, sensitivity, and limits of detection of monitoring methods used in the aseptic processing of healthcare products.”
(1116) Microbiological Control and Monitoring of Aseptic Processing Environments.
The United States Pharmacopeial Convention
Official from May, 1 2015.