This document applies to welded composite enclosures of cast and wrought aluminium alloy pressurized with dry air@ inert gases (e.g. sulphur hexafluoride or nitrogen or a mixture of such gases)@ used in indoor and outdoor installations of high-voltage switchgear and controlgear with rated voltages above 1 kV@ where the gas is used principally for its dielectric and/or arc-quenching properties with rated voltages: ?? above 1 kV and up to and including 52 kV concerning gas-filled compartments with design pressure higher than 300 kPa relative pressure (gauge); ?? above 52 kV concerning all gas-filled compartments. The enclosures comprise parts of electrical equipment not necessarily limited to the following examples: ?? circuit-breakers; ?? switch-disconnectors; ?? disconnectors; ?? earthing switches; ?? current transformers; ?? voltage transformers; ?? surge arrestors; ?? busbars and connections; ?? etc. The scope also covers enclosures of pressurized components such as the centre chamber of live tank switchgear@ gas-insulated current transformers@ etc