6.2 Fan lawsThe fan laws (as defined in 7.1.5.1 and ISO 5801) shall serve as the basis for calculating the performance ratings of fans from tests of other sizes and speeds. Fan laws shall not be used for calculating the performance of a smaller sized fan from the testing of larger fans.6.3 Check-tests Products licensed under a certified ratings programme shall be subject to periodic check-tests at not more than at intervals of 36 months. When products are check-tested, the performance should be within the tolerance for airflow, pressure, power and efficiency (if certified), as defined below, when compared to the catalogue data published by the manufacturer. The check-tests shall be made using the same laboratory set-up and installation category as used by the fan manufacturer to collect the original data.For products catalogued using constant or as-run speed tables, the tolerance shall be applied to the catalogue points only. For products catalogued using multi-rating tables or curves, the tolerance shall be applied over the performance range catalogued.