An apparatus on a carding machine has a covering comprising work and cover elements lying opposite the clothing of a high-speed cylinder. There is, in succession, an air exhaust opening for the exit of air and an opening for entry of air, past which openings a flow of fibers and air is passed. To allow improved detachment and elimination of short fibers in a simple manner, the spacing of the covering upstream of the exhaust opening is smaller than the spacing of the covering between air exhaust opening and air inlet opening and an airflow flows against the direction of rotation of the cylinder along the surface of the cylinder and flows with short fibers through the air exhaust opening.