ISO 29461 specifies methods and procedures for determining the performance of particulate air filters used in air intake filter systems for rotary machinery such as stationary gas turbines, compressors and other stationary internal combustion engines. It applies to air filters with an efficiency of 85 % or more for the MPPS (EPA and HEPA filters) which are tested according to ISO 29463 part 1 to 5 and filters with a lower efficiency which are tested according to ISO 16890 part 1 to 4. The procedures described in both, the ISO 16890 series and the ISO 29463 series, are applied and extended by this part of ISO 29461 to air filters which operate at flow rates within the range 0,24 m3/s (850 m3/h, 500 ft3/min) up to 2,36 m3/s (8500 m3/h, 5000 ft3/min). This part of ISO 29461 refers to static (barrier) filter systems but can also be applied to other filter types and systems in appropriate circumstances, for example to evaluate the initial efficiency of cleanable and surface loading filters. The performance results obtained in accordance with this part of ISO 29461 cannot be quantitatively applied (by themselves) to predict performance in service with regard to efficiency and lifetime. Other factors influencing performance to be taken into account are described in the annexes.