Abstract: Molten steel, normally exposed to an atmosphere of air, is protected against impurities by placing a gas containing a major amount of carbon dioxide gas in such quantities and in such proximity to the surface to cause dissociation of the carbon dioxide at a rate which provides a gas barrier or shroud isolating the steel from the surrounding atmosphere. This method may be applied to protecting certain molten steels being transferred from a ladle to a mold, or from a ladle to a tundish and from the tundish to a mold in continuous casting. In a method where a number of shrouding operations are carried out in series, gas under pressure is bled, in increments, from a storage vessel containing a body of liquid carbon dioxide in an overlying ullage space containing vapor. Each increment is ultimately expanded and dispersed at ambient temperature to form the shroud.