Compressed gas circuit breaker

In a compressed gas circuit breaker including a first fixed arc contact (2), a second moving arc contact (7), said breaker being provided both with a blast device comprising a piston (12), a cylinder (3A) and means defining a blast orifice (10B) for sending a jet of compressed gas to the zone where an electric arc forms when the arc contacts (2, 7) separate, and means defining a volume (9) containing a gas suitable for being heated by the action of the arc, said means defining said volume including an opening (10A) to enable the hot gas to escape, said means defining said blast orifice (10B) and said opening (10A) being annular and disposed side by side, the improvement wherein said blast orifice (10B) is disposed at one end of an annular volume (4) delimited by a circularly symmetrical blast nozzle (14) and a circularly symmetrical deflector (5), said volume (9) being delimited by said deflector (5) and said second arc contact (7), and the opening (10A) of said volume being situated next to said blast orifice (10B), and said opening and said blast orifice being positioned relative to said first and second arc contacts, such that the opening (10A) of said volume and said blast orifice (10B) are closed by said first arc contact (2) when the circuit breaker is closed, and said opening (10A) and said orifice (10B) are opened in succession by relative displacement of the arc contacts (2, 7).