The present invention relates to an air gap device for a medical instrument cleaning and disinfecting apparatus, the device comprising a housing having a first end adapted to allow liquid to enter the device and a second end adapted to discharge liquid from the device, wherein the first end comprises means for connecting the device to a disinfecting unit. The device further comprises handling means for handling the device. The present invention relates to a liquid disinfecting cartridge comprising the air gap device and the liquid disinfecting unit. Further, the present invention relates to a liquid disinfecting unit and air gap device intended for use in the liquid disinfecting cartridge and relates to an assembly of the medical instrument cleaning and disinfecting apparatus and the liquid disinfecting cartridge. The invention also relates to a method for interchangeably coupling the liquid disinfecting cartridge with the medical instrument cleaning and disinfecting apparatus.
