Recycling of hydrogen and helium from the SS 304 wall of a plasma discharge experiment has been studied. Hydrogen recycling was dominated by diffusion and recombination; however, helium recycling was dominated by trapping. Detrapping of both hydrogen and helium was observed during a discharge of the opposite species. The density of trapped H from previous hydrogen discharges is estimated to be 1.4×1015 cm−2. Vacancies created in the oxide layer by the implanted ions are suggested as the trapping mechanism.