This part of ISO 29463 specifies the reference test procedure for determining the efficiency of filters at their most penetrating particle size (MPPS). It also gives guidelines for the testing and classification for filters with an MPPS of less than 0,1 µm (Annex B) and filters using media with (charged) synthetic fibres (Annex C). It is intended for use in conjunction with ISO 29463-1, ISO 29463-2, ISO 29463-3 and ISO 29463-4.