An apparatus for inspecting a sample, is equipped with a charged particle column for producing a focused beam of charged particles to observe or modify the sample, and an optical microscope to observe a region of interest on the sample as is observed by the charged particle beam or vice versa. The outlet orifice of the collecting chamber has a smaller cross section than the inlet orifice, and the sensor is a level sensor that transmits signals to an evaluation apparatus, by which an entire functioning of the rotating liquid-discharging appliance can be monitored. Upon contact with the air stream, the condensed water evaporates into the air stream, resulting in a humidified air stream.