This European Standard specifies a colour coding system for the secondary method of identification of the contents of gas cylinders for industrial gases, breathing gas application and gases for medical use with particular reference to the properties of the gas or gas mixture. This European Standard does not apply to cylinders containing liquefied petroleum gas (LPG), to refrigerant gases, to portable fire extinguishers or stationary cylinder extinguishing. Cylinder bundles are not covered in this document, for bundle identification see ISO 10961. NOTE LPG includes substances carried under the UN number 1965 "Hydrocarbon gas mixture, liquefied, N.O.S."