An electrical power switch operating with a pressurized gas for actuating the switch contacts and also providing a quenching action in which the arc is lengthened and extinguished includes a container in which the pressurized gas is stored, the outlet from this container being located adjacent the junction area between a plurality of contact fingers in fixed position and a movable contact member that also includes a valve member for closing off the gas outlet from the container when the switch contacts are closed. When the movable contact is released for initiating an opening operation of the contacts, the pressure of the gas stored in the container forces the valve open thus releasing the gas for blasting the arc drawn between the contacts. The gas enters an annular chamber surrounding the junction line of the contacts which includes two half-turn helical travel rails of different radius and opposite winding sense to which the feet of the arc are transferred from the contacts and travel downward and into a group of circumferentially spaced nozzles in which the arc is further lengthened.