The report presents the results of several dedicated series of tests to assess the SEF of axial and centrifugal fans, which show that in most cases the SEF is not much important except in some special situations such as a wall in front and very close to the inlet of an axial fan, a cabinet with a lateral opening of small cross-section at the inlet of a BC or FC centrifugal fan, or an outlet plenum with side walls close to the impeller of a plenum fan.