The patterns of gas exchange between deuterium plasma and the walls of a vacuum chamber made from 12Cr18Ni10Ti (0.12% C, 18% Cr, 10% Ni, less than 1% Ti) stainless steel and irradiated with deuterium atoms in an atmosphere of deuterium with the addition of oxygen or with ions and atoms of a discharge in deuterium with the addition of oxygen are studied. It is demonstrated that irradiation of the surface of stainless steel under the indicated conditions promotes the diffusion of hydrogen from stainless steel; the implantation of deuterium into stainless steel; and the production on the surface and the desorption of H 2 O, HDO, D 2 O, HD, and H 2 molecules. Almost all oxygen from the gas mixture in the oxygen concentration range from 0.5 to 30 at % is involved in the production of protonated and deuterated water molecules on the surface. When the oxygen concentration in the mixture of deuterium with oxygen is increased, the release of hydrogen from steel is enhanced. The amount of deuterium captured by stainless steel is lower than the amount of hydrogen removed from it. It is demonstrated that the diffusion of hydrogen towards the surface, its reactions with deuterium and oxygen from the working gas, and the trapping of deuterium in steel may be driven by consecutive surface exothermic reactions initiated by the interaction of deuterium atoms and ions with chromium oxide on the surface of stainless steel.