Requirements for switches rated 72.5 kV and above, intended for use in metal-enclosed, gas-insulated substations, are presented. These switches are characterized by grounded, leak-tight metal enclosures that are filled with a gas (most commonly sulfur hexafluoride, SF6) at some pressure above atmospheric. Live parts are contained within the housing and insulated thereefrom by the gas and by suitable solid insulation that supports the live parts in their proper position. Gas-insulated switches are normally electrically connected to and structurally joined to other gas-insulated components, such as buses, gas-to-air bushings, circuit breakers, instrument transformers, cable terminations, etc. Switches may be manually or power operated. Service conditions, ratings, supporting structures, and nameplates are covered. Testing of disconnecting and grounding switches is covered.