Abstract: An air replenishment unit more particularly for suspension under ceilings of clean rooms, including a housing whose wall is provided with a fan on the intake side, an outlet opening of the housing being functionally connected with an air filter arrangement. The strip-like housing having the fan is bent on the intake side at two opposite sides in an arcuate manner toward the output side, the two longitudinal edges of such wall being joined to two side walls, which are essentially parallel to each other, by folded sheet joints. The free edges, not having any folded joints, of the strip-like wall and the side walls essentially define an outlet opening. Such a housing together with a fan may be produced simply, economically and with a light weight using only three pre-stamped parts using folded or crimped seams and then constitutes a single-piece downwardly open hood-like housing with high class flow properties.