Anesthesia gas supply in the operating room
Anesthesia gases in the operating room environment are usually supplied from a wall outlet. In the US, the connections between the wall supply and the high pressure hoses leading to the anesthesia machine are made either through the diameter index safety system (DISS) or the Ohio quick connect system. Wall outlets and hoses are color coded for the gas they carry.
Oxygen, air, and nitrous oxide are supplied in this way. In some anesthesia locations, especially in non-operating room environments, nitrous oxide is not supplied from a wall outlet. Anesthesia machines carry a bank of gas cylinders, which are either the sole source or a back-up supply if the wall outlets fail.
Gas tanks/ cylinders
The connection between a gas cylinder and an anesthesia machine is through a pin index safety system which is designed (like the OQC and DISS are) to prevent false connections.
Pin index safety system connection on N2O cyclinder
Pin index safety system conection between N2O cylinder and receiver on anesthesia machine
Srivastava, Uma (2013): Anaesthesia gas supply. Gas cylinders. In Indian Journal of Anaesthesia 57 (5), pp. 500–506. DOI: 10.4103/0019-5049.120147.