ABSTRACT
Aseptic processing using sterilizing grade membrane filtration has been practiced with reliability and safety for years. Nevertheless, to prove its reliability and safety, one has to integrity test air filters. Sterilizing grade filtration is an acceptable process only if the filter has been integrity tested. This fact is established in several guidelines recommending the use of integrity testing both before and after filtration. The integrity of the filter assembly should be checked by an appropriate method, such as bubble-point pressure test or forward-flow pressure test immediately before and after use. Abnormal filtration flow-rates should be noted and investigated. Results of these filter integrity checks should be recorded in the batch record. Of all the structural features characterizing a filter, none would seem more pertinent to particle retention, whether of viable or nonviable particles, than its pore size.
