Abstract: The invention relates to a process for protecting a non-ferrous liquid metal from oxidation and from firing in a machine processing this metal or its alloys, consisting of disposing a gaseous mixture containing carbon dioxide at the surface of the non-ferrous metal. According to this process, the gaseous mixture is prepared by adding to the carbon dioxide an oxidising gas, argon and xenon only, this gaseous mixture having properties ensuring protection from the ambient atmosphere, and the proportion of carbon dioxide in this gaseous mixture ranging from 50% to 90% by volume.