A beam for a suspended ceiling in a clean room has soft plastic flaps on top of the flanges. The present invention also relates to a motor driven unit, for example a motor vehicle. The connecting wall has a rearwall-connecting portion connected to the rearwall, and a frontwall-connecting portion connected between the frontwall and the rearwall-connecting portion and having a thickness smaller than that of the rearwall-connecting portion so as to allow for floating movement of the frontwall relative to the rearwall. A part of the elastic conductive body is compressed by the bosses and connection resistance with the elastic conductive body is reduced. The cover member includes a carrier gas cover inlet, a liquid source cover inlet, a source cover outlet which extends from a first outer surface through the cover member to the second inner surface.