A female connecting device used to accept a male nitrous oxide/oxygen connector to connect two devices together to provide a continuous passageway for the delivery of a mixture of 50% nitrous oxide (N2O) and 50% oxygen (O2). It has safety features such as a specific mechanical mating pattern, colour coding and a dedicated tube diameter connection to prevent wrong connection and allow a user to rapidly connect and disconnect nitrous oxide/oxygen dependent devices. It can be designed as a diameter-indexed safety system (DISS) connector or a non-interchangeable screw-threaded (NIST) connector. This is not a nitrous oxide/oxygen terminal unit.