Abstract: The present invention relates to an improved arc chamber/chute assembly in a circuit breaker for effective channelization of hot ionized gases through said arc chamber to enhance breaking capacity in circuit breakers. The assembly comprises back vent secured inside said arc chute assembly and front vent secured inside the assembly placed between the back vent and arc chute plates of the assembly. The front vent comprises a substantially T-shaped profile having a substantially horizontal portion along X-axis and a substantially vertical portion along Y-axis so as to define a substantially divergent nozzle profile in the said T-shaped profile such that at the time of high fault conditions in said arc chamber nozzle effect is generated due to high pressure build up in arc chamber assembly.