Abstract: An improvement to the lock elements of a filter ventilator that is engaged in an opening in a fastening plate in such a manner that a housing part with an outer cross section that corresponds to the cross section of the opening includes a stop flange that limits insertion of a filter on the fastening plate and lock elements arranged on the outside of the housing part wherein the spring-like elements each have a free end attached to the housing part such that the free end is oriented toward a support surface on the rear side of the stop flange, the ends of the lock elements include a plurality of lock stages oriented in a stepped arrangement so as to form a locating section substantially perpendicular to the support surface and a lock section that is substantially parallel to the support surface where the lock sections include spaces of equal width and the locating sections are sized for varying thicknesses of fastening plates, and the lock stage nearest the support surface includes a space with respect to the