A scrubber for eliminating NO from air flowing through the scrubber, comprising a housing (1) having at least one inlet hole (2) and an outlet hole (4) and which is comprising filtering material (6). A second outlet hole (9) is provided in the housing (1) at a position situated at a distance from the first outlet hole (4) and any inlet hole (2) so that the air leaving the second outlet hole (9) will have flown at least through a depth of the filtering material (6) substantially corresponding to the depth of the filtering material (6) for the air flowing from the inlet hole (2) to the first outlet hole (4).