CIRCUIT BREAKER

A circuit breaker is disclosed which has first and second electrodes that can be contacted to complete a circuit or withdrawn from each other by some suitable mechanism to break the circuit. During breaking of the circuit, an electric arc is created. The circuit breaker includes means for providing gas pressure below atmosphere around the electrodes, at least at the time the arc is struck. The circuit breaker also includes a shield arranged in proximity to the electrodes which is ablated by the action of the arc. The shield's arrangement and material are chosen such that, when ablated, the shield releases gas to assist in extinguishing the arc.