Abstract: A filter fan of a switch cupboard or of an electrical and/or electronic device placed in a casing with a blast producing an air flow and with a filter element (3) which is placed in the air flow and separates a clean side, on which the blast is placed, from an unclean side, wherein the filter element is held in a frame which can be fixed on the casing by covering the air passage opening penetrating through the casing wall and wherein a protective grid (4) is placed between the filter element (3) and the blast, the invention proposes that a bridging-free distance is provided between the filter surface of the filter element (3) and the protective grid (4), wherein this distance is dimensioned so as to make possible the discharge of water drops on the clean side surface of the filter element and to avoid a contact of the water drops with the protective grid.