Abstract: In the opening and cleaning of fibrous materials apparatus is provided which includes a plurality of rotatable beaters within a housing, curved under grids beneath each rotatable beater, baffle plates above and between the beaters, a perforated screen positioned above and adjacent the beaters and a suction hood positioned over and embracing the whole upper surface of the perforated screen. The screen is inclined to the horizontal and the apparatus includes a suction duct extending across the lowermost edge for withdrawing air from an inlet slot along the opposite edge to create an air stream flowing over the whole surface of the screen such that dust and unusable fibres passing through the screen are carried away to a waste extraction duct.