Abstract: An air treatment unit for treatment of an air stream, including a pad having a multitude of narrow air-flow channels, the walls of which are formed by corrugated sheets of a stiff material, the sheets being positioned and fixed generally in parallel planes next to each other in such a way that, as seen from an inlet side of the pad to an outlet side thereof, the channels formed by the corrugations of any two sheets located next to each other extend in two different directions the vertical plane of the respective sheet. At least in a central region of the pad, all sheets are positioned obliquely sideways, whereby all channels extend obliquely sideways relative to inlet and outlet surfaces of the pad.