The plenum boxes, made of galvanized sheet steel, are optimized for the air diffusers and for low installation heights, also available with powder coating. One or two lateral connecting pieces or one for connection from above as standard. In addition, with dampers and special air deflector plates for optimum air distribution with low flow noises, particularly for supply air. Setting volume flow rate is possible without dismounting of the air diffuser. With suspension holes and concealed central fastening. For closed ceiling systems, grid ceilings and for freely suspended.