The invention provides a milking device comprising at least one milking cup with a teat space and a pulsation space, a pulsator connected by means of a pulsation line to the pulsation space of the milking cup and provided with a vacuum source, a vacuum line provided with a first controllable valve between the vacuum source and the pulsation line, an aeration line provided with a second controllable valve between the pulsation line and a source of higher pressure, and a pulsator control system for the first and second valves, wherein the pulsator control system comprises a flushing mode for opening and holding open the first and second valves during at least a predefined flushing time which is at least as long as and preferably longer than the pulsation period. In this way it is possible to have both valves open simultaneously and the pulsator will draw in air from the environment in an initially unhindered flow. This flow may be used for example to flush the system with air (“blow through”) but also for example to measure the air flow and/or pressure drops in the system, and on the basis thereof to determine the degree of soiling of the system.