This International Standard specifies requirements for the classification of gases and gas mixtures used in fusion welding and allied processes including, but not limited to: - tungsten arc welding (Process 141); - gas-shielded metal arc welding (Process 13); - plasma arc welding (Process 15); - plasma arc cutting (Process 83); - laser welding (Process 52); - laser cutting (Process 84); - arc braze welding (Process 972). NOTE Process numbers are in accordance with ISO 4063. The purpose of this International Standard is to classify and designate shielding, backing, process and assist gases in accordance with their chemical properties and metallurgical behaviour as the basis for correct selection by the user and to simplify the possible qualification procedures. Gas purities and mixing tolerances are specified as delivered by the supplier (manufacturer) and not at the point of use. Gases or gas mixtures may be supplied in either liquid or gaseous form, but when used for welding and allied processes, the gases are always used in the gaseous form. Fuel gases, such as acetylene, natural gas, propane, etc., and resonator gases, as used in gas lasers, are not covered by this International Standard. Transportation and handling of gases and containers shall be in accordance with local, national and regional standards and regulations as required.