Abstract: A cyclone separator has a filter unit which is disposed inside a central outlet between an inlet chamber of the cyclone separator (for gas mixed with dust) and an outlet chamber thereof (for clean gas) connected to a suction source. A method is provided for cleaning such a cyclone separator by momentarily establishing a connection between the outlet chamber and the atmosphere. The communication between the inlet chamber and the suction source being maintained, to initiate a rapid pressure rise in the outlet chamber and thus a reverse gas flow through the filter unit. The outlet chamber of the cyclone separator has a valve controlled aperture for connecting the outlet chamber to the atmosphere, a closure member of the valve being biased to a closed position by existing pressure difference between the outlet chamber and the atmosphere.