Filter unit for a switchgear cabinet

A filter unit for a switchgear cabinet, comprising a filter mat and filter housing having an air passage that can be covered by an air passage grating at least to some extent, wherein the air passage grating is hinged indirectly or directly to the filter housing by a hinge defining a single horizontal axis around which the air passage grating may be moved between a closed position and an opened maintenance position, and the filter housing has a retainer which is formed to the housing via a spring element and positively blocks a catch of the air passage grating in the maintenance position, wherein the retainer and the catch are configured such that when the air passage grating is pivoted relative to the filter housing to a specific adjustment angle, the air passage grating reaches a position where the catch meets the retainer, wherein upon further pivoting the air passage grating, a friction surface of the retainer slides along a counter friction surface of the catch and the spring element is resiliently deviated upwardly and applies a pressure force to the catch, and wherein each retainer and catch comprises a hook-shaped tab, which engage each other in the maintenance position.