A method for operating a dirt collecting device for a sweeping vehicle or for a vacuum cleaner nozzle of a floor or upright vacuum cleaner, each having a suction fan with controllable speed and/or power, wherein
- in a first method step, which corresponds to normal operation, the suction power of the suction fan is set at such a low level that the suction pressure in the dirt collecting device or the vacuum cleaner nozzle is merely sufficient to convey and deposit the input coarse dirt into the intermediate container, and to convey the absorbed input fine dirt into a downstream collection container;
- in a second method step, the filling level in the intermediate container is detected with respect to the coarse dirt deposited therein;
- and
- in a third method step, which corresponds to an emptying mode, if the filling level in the intermediate container is exceeded, the suction power of the suction fan is increased such that the coarse dirt, which is temporarily deposited in the intermediate container, becomes dispersible and is conveyed into the downstream collection container.