A change-over switch comprising: a frame having a first side wall and a second side wall facing substantially opposite direction relative to the first side wall, the first side wall and the second side wall being spaced apart in a longitudinal direction; a first supply terminal adapted to be connected to a first power supply; a second supply terminal adapted to be connected to a second power supply; a load terminal adapted to be connected to a load; a selector contact adapted to rotate relative to the frame around a rotation axis between a first position in which the selector contact electrically conductively connects the first supply terminal to the load terminal, and a second position in which the selector contact electrically conductively connects the second supply terminal to the load terminal, wherein electrically conductive connection between the selector contact and the first supply terminal is adapted to be closed and opened in a first contact zone, and electrically conductive connection between the selector contact and the second supply terminal is adapted to be closed and opened in a second contact zone; and a gas discharge arrangement for discharging gasses produced by switching events from the frame, the switching events comprising a first type switching event occurring between the selector contact and the first supply terminal, and a second type switching event occurring between the selector contact and the second supply terminal, the gas discharge arrangement comprising a first gas discharge passage, a second gas discharge passage and at least one gas flow opening (31, 32), wherein the at least one gas flow opening (31, 32) is formed in the frame, and adapted to provide a flow path for the gasses from inside the frame to outside the frame, the first gas discharge passage originating from the first contact zone and ending to the at least one gas flow opening (31, 32), and the second gas discharge passage originating from the second contact zone and ending to the at least one gas flow opening (31, 32), characterized in that the first supply terminal and the second supply terminal project from the first side wall, and the load terminal projects from the second side wall, and the at least one gas flow opening (31, 32) is formed in the second side wall. a frame having a first side wall and a second side wall facing substantially opposite direction relative to the first side wall, the first side wall and the second side wall being spaced apart in a longitudinal direction; a first supply terminal adapted to be connected to a first power supply; a second supply terminal adapted to be connected to a second power supply; a load terminal adapted to be connected to a load; a selector contact adapted to rotate relative to the frame around a rotation axis between a first position in which the selector contact electrically conductively connects the first supply terminal to the load terminal, and a second position in which the selector contact electrically conductively connects the second supply terminal to the load terminal, wherein electrically conductive connection between the selector contact and the first supply terminal is adapted to be closed and opened in a first contact zone, and electrically conductive connection between the selector contact and the second supply terminal is adapted to be closed and opened in a second contact zone; and a gas discharge arrangement for discharging gasses produced by switching events from the frame, the switching events comprising a first type switching event occurring between the selector contact and the first supply terminal, and a second type switching event occurring between the selector contact and the second supply terminal, the gas discharge arrangement comprising a first gas discharge passage, a second gas discharge passage and at least one gas flow opening (31, 32), wherein the at least one gas flow opening (31, 32) is formed in the frame, and adapted to provide a flow path for the gasses from inside the frame to outside the frame, the first gas discharge passage originating from the first contact zone and ending to the at least one gas flow opening (31, 32), and the second gas discharge passage originating from the second contact zone and ending to the at least one gas flow opening (31, 32), the first supply terminal and the second supply terminal project from the first side wall, and the load terminal projects from the second side wall, and the at least one gas flow opening (31, 32) is formed in the second side wall.