ISO/FDIS 21220

ISO 21220:2008 refers to particulate air filters for general ventilation. It describes testing methods and the test rig for measuring filter performance. The test rig is designed for an air flow rate between 0,25 m3/s (900 m3/h, 530 ft3/min) and 1,5 m3/s (5 400 m3/h, 3 178 ft3/min). ISO 21220:2008 applies to air filters having an initial efficiency of less than 99 % with respect to 0,4 �m particles. Filters in the higher end and above 99 % initial efficiency are tested and classified according to other standards. Two test methods are combined in ISO 21220:2008: a “fine method” for air filters in the higher efficiency range and a “coarse method” for lower efficiency filters. In either case, a flat sheet media sample or media pack sample from an identical filter shall be conditioned (discharged) to provide information about the intensity of the electrostatic removal mechanism. After determination of its initial efficiency, the untreated filter is loaded with synthetic dust in one step until its final test-pressure drop is reached. Information on the loaded performance of the filter is then obtained. The performance results obtained in accordance with ISO 21220:2008 cannot, by themselves, be quantitatively applied to predict performance in service with regard to efficiency and lifetime. It is necessary to take into account other factors influencing performance.