Air duct

An air duct (1) having a recess (8) for receiving a filter (5). The duct (1) has a wall (4) wherein a part (6) of the wall extends into the duct (1). Said wall part (6) is provided with an element (7) which extends perpendicular to the wall part (6). The element (7) and the wall part (6) define a recess (8) within the duct (1) for receiving a filter (5). The recess (8) has an aperture through to the duct and when a filter (5) is fitted, said element (7) abuts with the filter (5) and said wall part (6) engages with a sealing means (10) associated with the filter (5).