This electrical circuit breaker includes at least one first fixed land, a support assembly equipped with at least one second land rotationally mobile, about a main axis, between a first position in which the second land is in contact with the first land and a second position in which the second land is separated from the first land and an arc-extinguishing chamber including a stacking of plates, a top arc-guiding horn, a bottom arc-guiding horn, equipped with at least one tab and a screen made of insulating material surrounding the bottom arc-guiding horn. The circuit breaker also includes two protuberances produced in a gas-producing material, which are mounted on the screen, arranged between the bottom horn and the top arc-guiding horn and facing the tab of the bottom arc-guiding horn, the protuberances having a prismatic or pseudo-prismatic form.