Abstract: A compressed gas circuit breaker, especially a blasting piston ("puffer") circuit breaker having a movable nozzle of insulating material which surrounds the quenching gap and, by means of pressure springs, forms a stop for closing off the gas flow canal, in which a guide is provided coupling at least one pressure spring to the relative motion of the contacts in such a manner that its effect on the insulating material body is cancelled as soon as the minimum quenching distance has been reached during the opening of the breaker, preventing blasting of the arc before the switch contacts have reached their quenching distance.