The heavy-duty circuit-breaker with arc blowing has an element which is sensitive to hot gas and/or to gas pressure and is protected by means of a seal against a hot-gas flow. The seal is advantageously a movable non-contacting seal. The seal has a channel entrance for production of a partial hot-gas flow of the hot-gas flow and, connected downstream from this, a channel in order to reduce the mass flow of the partial hot-gas flow, and an expansion chamber in order to expand the volume of the partial hot-gas flow. The expansion chamber is a pressure-relief area. The element may, for example, be a guide element, a contact-making element or a sealing element.