Applies to fusion welded wrought steel enclosures pressurized with dry air, inert gases, e.g. sulfur hexafluoride or nitrogen or a mixture of such gases, used in indoor or outdoor installations of high voltage switchgear and controlgear with rated voltages 72,5 kV and above, where the gas is used for its dielectric and/or arc quenching properties. Enclosures comprise parts of electrical equipment such as circuit breakers, switch disconnectors, earthing switches, current and voltage transformers, surge arrestors and bushbars and connections. Includes pressurized components such as centre chamber of live tank switchgear, gas insulated current transformers, etc.