An electric arc-blast nozzle (20, 30, 40, 50, 60, 70) for a circuit breaker comprising: a neck-forming median part (27, 37, 47, 57, 67, 77) internally defining an axial passage for cutting the electric arc and formed with a first dielectric material obtained from a first composition comprising a fluorocarbon polymer matrix, two end parts (9, 11, 41, 51) extending on either side of the median part (27, 37, 47, 57, 67, 77) which are respectively intended to receive the arc contacts and that can be axially moved in relation to each other, between a circuit breaker opening position in which the arc contacts and are separated from each other and a circuit breaker closing position in which the arc contacts and are in contact with each other and in which one of the arc contacts partially closes the axial passage of the median part (27, 37, 47, 57, 67, 77), an electric arc cut-off gas circulating in the axial passage of the median part (27, 37, 47, 57, 67, 77) to cut an electric arc that is likely to be formed during the movement of the arc contacts and from the closing position to the opening position of the circuit breaker, and an insert (22, 32, 42, 52, 62, 72), whereby said insert (22, 32, 42, 52, 62, 72) defines a downstream area of the axial passage of the median part (27, 37, 47, 57, 67, 77) considering the direction of the flow of the electric arc cut-off gas and is, also, formed with a second dielectric material, different from the first dielectric material and chosen from among: a composite material obtained from a second composition comprising a fluorocarbon polymer matrix and characterised by; at least one inorganic filler A chosen from among a sulfur, preferably MoS 2, Sb 2 S 5 or Sb 2 S 3, a ceramic, preferably BN, and an oxide chosen from among SiO 2, TiO 2, Al 2 CoO 4, ZnO, BaTiO 3 and P 2 O 5, preferably SiO 2, in a percentage weight ranging between 0.1 % and 10 %, with respect to the total weight of the second composition, and/or at least one inorganic filler B chosen from among a graphite, a mica, a glass and a fluoride, preferably CaF 2, in a percentage weight ranging between 5 % and 50 %, with respect to the total weight of the second composition, and a ceramic material obtained from a third composition comprising at least one compound chosen from among a carbide, a boride and an oxide. a neck-forming median part (27, 37, 47, 57, 67, 77) internally defining an axial passage for cutting the electric arc and formed with a first dielectric material obtained from a first composition comprising a fluorocarbon polymer matrix, two end parts (9, 11, 41, 51) extending on either side of the median part (27, 37, 47, 57, 67, 77) which are respectively intended to receive the arc contacts and that can be axially moved in relation to each other, between a circuit breaker opening position in which the arc contacts and are separated from each other and a circuit breaker closing position in which the arc contacts and are in contact with each other and in which one of the arc contacts partially closes the axial passage of the median part (27, 37, 47, 57, 67, 77), an electric arc cut-off gas circulating in the axial passage of the median part (27, 37, 47, 57, 67, 77) to cut an electric arc that is likely to be formed during the movement of the arc contacts and from the closing position to the opening position of the circuit breaker, and an insert (22, 32, 42, 52, 62, 72), whereby said insert (22, 32, 42, 52, 62, 72) defines a downstream area of the axial passage of the median part (27, 37, 47, 57, 67, 77) considering the direction of the flow of the electric arc cut-off gas and is, also, formed with a second dielectric material, different from the first dielectric material and chosen from among: a composite material obtained from a second composition comprising a fluorocarbon polymer matrix and characterised by; at least one inorganic filler A chosen from among a sulfur, preferably MoS 2, Sb 2 S 5 or Sb 2 S 3, a ceramic, preferably BN, and an oxide chosen from among SiO 2, TiO 2, Al 2 CoO 4, ZnO, BaTiO 3 and P 2 O 5, preferably SiO 2, in a percentage weight ranging between 0.1 % and 10 %, with respect to the total weight of the second composition, and/or at least one inorganic filler B chosen from among a graphite, a mica, a glass and a fluoride, preferably CaF 2, in a percentage weight ranging between 5 % and 50 %, with respect to the total weight of the second composition, and a ceramic material obtained from a third composition comprising at least one compound chosen from among a carbide, a boride and an oxide.