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.