Filtration device

The filter assembly, especially for a motor vehicle's ventilation system, has a filter provided in a filter cover, and a housing with an inlet opening (13) in which the filter cover is located. An insertion bevel is provided in the housing. The filter cover has a section (11) with a width (B) greater than the width (b) of the insertion opening in the housing, whereby the aforesaid section is located on the side of the insertion bevel. The housing is widened in the region of the insertion bevel, with the widening formed by a wedge-shaped insertion passage (15).