This part of ISO 16890 establishes an efficiency classification system of air filters for general ventilation based upon Particulate Matter (PM). It also provides an overview of the test procedures, and specifies general requirements for assessing and marking the filters, as well as for documenting the test results. It is intended for use in conjunction with ISO 16890 2, ISO 16890 3 and ISO 16890 4. The test method described in this standard is applicable for air flow rates between 0,25 m3/s (900 m3/h, 530 ft3/min) and 1,5 m3/s (5 400 m3/h, 3 178 ft3/min), referring to a test rig with a nominal face area of 610 mm × 610 mm (24 inch × 24 inch). ISO 16890 (all parts) refers to particulate air filter elements for general ventilation having an initial efficiency less than or equal to 99 % with respect to PM1 aerosol fraction and greater than 20 % with respect to PM10 aerosol fraction when tested per the procedures defined within parts 1-4 of ISO 16890. Air filter elements outside of this aerosol fraction are evaluated by other applicable test methods, (see ISO 29463, part 1-5). Filter elements used in portable room-air cleaners are excluded from the scope of this standard. The performance results obtained in accordance with this series of standards shall not by themselves be quantitatively applied to predict performance in service with regard to efficiency and lifetime. Other factors influencing performance to be taken into account are described in Annex A (informative).