Annex 1, paragraph 85 states, ‘the integrity of the sterilised filter should be verified before use and
should be confirmed immediately after use by an appropriate method such as a bubble-point,
diffusive-flow or pressure-hold test.’
The filter sterilisation process may be physically stressful for the filter. For example, high temperatures
during the process may cause the filter to distort, potentially leading to fluid pathways that allow the
passage of particles greater than 0.2 µm in size. The performance of a filter can improve with use, as
particles begin to block individual pathways and remove larger pathways that smaller particles could
successfully navigate. For these reasons, filters should be tested both before use but after sterilisation
and again after use.
Furthermore, testing should be performed in situ in order to verify the integrity of the filter complete
with its housing.
