This document establishes a conditioning method to determine the minimum fractional test efficiency. It is intended to be used in conjunction with ISO 16890‑1, ISO 16890‑2 and ISO 16890‑3, and provides the related test requirements for the test device and conditioning cabinet as well as the conditioning procedure to follow. The conditioning method described in this document is referring to a test device with a nominal face area of 610 mm × 610 mm (24 inches × 24 inches). This document refers to particulate air filter elements for general ventilation having an ePM1 efficiency less than or equal to 99 % and an ePM10 efficiency greater than 20 % when tested according to the procedures defined within the ISO 16890 series. NOTE The lower limit for this test procedure is set at a minimum ePM10 efficiency of 20 % since it will be very difficult for a test filter element below this level to meet the statistical validity requirements of this procedure. Filter elements used in portable room-air cleaners are excluded from the scope of this document.