An ejector is provided with an interior surface wetting device for introducing a cleaning liquid into a suction chamber of the ejector to form a thin wall of the cleaning liquid covering an interior surface of the ejector. The interior surface wetting device includes a cleaning liquid inlet opening to be fluidly connected to a source of cleaning liquid and a cleaning liquid outlet opening for introducing the cleaning liquid into a suction chamber. The wetting device may be in the form of a pipe which extends from the outside of the ejector into the suction chamber to supply a cleaning liquid to a desired portion in the suction chamber.