When a redundant filtration system is employed in production (Note: Two sterilizing-grade filters in series do not necessarily constitute a redundant filtration system. Please refer to the previous article: Is Redundant Filtration Just Unnecessary Filtration?), it is not always necessary to perform integrity tests on both filters after each use.
After Use of a Redundant Filtration System
It is recommended to test the primary filter. If the primary filter passes the integrity test, the redundant filter does not need to be tested.
If the primary filter fails the integrity test, the redundant filter can be tested and should pass. In addition to documenting and investigating the failed primary filter, a risk assessment should be conducted to ensure that the connection and components between the two filters were intact during the batch production, posing no risk of contamination, and that the failure of the primary filter did not increase the risk of system contamination. In this scenario, a successful integrity test of the redundant filter is acceptable and can serve as the basis for batch release.
Before Use of a Redundant Filtration System
If the product is not intended for export to the European Union, an integrity test is generally recommended. However, in some cases, a risk assessment can determine whether to perform the test, which filter(s) to test (either stage or both), and whether to test before or after sterilization. For post-sterilization testing, the sterility of the assembly between the two filters must be ensured.
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