A high-voltage circuit breaker includes two arcing contacts, which are capable of moving relative to one another along an axis, an insulating nozzle, a heating volume for accommodating quenching gas, a heating channel, and an overpressure valve. The pressure of the quenching gas is based on the energy of a switching arc, which is formed when the breaker opens and generates arcing gas, and the heating channel opens out, with axial alignment, into the heating volume. The heating channel connects an arc zone, and the overpressure valve limits the pressure of the quenching gas by opening a relief duct, which opens out into an expansion space. In high-current switching, the pressure of the arcing gases in the arc zone is limited, and the quality of the quenching gas stored in the heating volume is improved, due to the relief duct having an outflow section extending in the radial direction.