Abstract: The present disclosure relates to a ventilation system module, VSM, arranged to be attached to an ambient facing surface of a building, the ambient surface being associated to at least one idle plane of a stairwell, the VSM being arranged to control air circulation of a plurality of spaces within said building, the VSM comprising a surface an air handling unit positioned at said surface, a distribution channel, an exhaust-air channel wherein said surface is arranged to be associated to said idle plane of said stairwell, wherein at an installed state of said VSM, the idle plane is accessible from a proximal portion of said surface.

Abstract: A filtering apparatus for an air treatment apparatus (5), a superior purity of the filtered air being required. The apparatus has a plurality of filter cartridges (3), provided with filters (2) and inserted into one cassette (4) each. The cassettes are fastened in the air treatment apparatus and the filter cartridges (3) have, on their side, which is turned towards the incoming air stream, a seal (6), which extends in an axial direction and around the periphery and axially abuts a surface, which is oriented radially in relation to the air stream and the apparatus or the like respectively and which surrounds an outlet opening (9), defined by each filter cartridge.