An apparatus for propelling a continuous gas mixture stream of an inert carrier gas and an aggressive doping gas, includes an electric motor having a motor housing filled with pure carrier gas and a shaft with a shaft extension, a radial blower having an impeller mounted directly on the shaft extension and a blower housing filled with the gas mixture and coupled to the motor housing, a gas ring of pure carrier gas being continuously fed and maintained in a ring space for sealing the blower housing against the motor housing in an operating state, and a hollow sealing ring being inflated with compressed gas for sealing the blower housing from the motor housing when the blower is stopped.