Abstract: A pyrotechnic circuit breaker comprising: a casing, at least two connection terminals, an internal electrical circuit connecting the two connection terminals and formed for example by an electrical conductor, an opening member, which is movable and arranged to open a part to be opened of the internal electrical circuit when moving between an initial position and a final position, so as to form at least two discrete portions of conductor after opening, a pyrotechnic actuator arranged to move the opening member from the initial position to the final position, an inner chamber defined by an internal wall formed in the casing, and receiving the part to be opened, an insulating grease, arranged in the inner chamber, wherein the insulating grease is arranged on or covers at least two predetermined parts of the internal wall.