An injector insert pipe is arranged in the gas channel of a nozzle for injecting oxygen-containing gas into a pig iron production unit, wherein an interspace which surrounds the pipe is present over the entire pipe length between the wall of the gas channel and the pipe outer wall. The pipe extends at least as far as the nozzle end face which contains the mouth of the gas channel. The pipe space is connected to an oxygen-containing gas feed line, and the interspace is connected to a protective gas supply line. In a process, oxygen-containing gas is fed into the pipe space, which after it has flowed through the pipe, enters the production unit at an entry velocity, and the interspace is simultaneously flowed through by a gas which exits into the production unit at an exit velocity, wherein the entry velocity is greater than the exit velocity.