A method of operating a device for the handling of containers, wherein the containers are conveyed at least locally through the device and are handled by the device in at least one pre-set manner, and wherein at least one flowable medium is used to operate the device. According to various aspects, pre-set areas of the device are irradiated by means of a radiation device in order to make at least one medium detectable in an area of the device in which the medium is present in a non-functional manner.