An EUV lithography system (1) includes: at least one optical element (13, 14) having an optical surface (13a, 14a) arranged in a vacuum environment (17) of the EUV lithography system (1), and a feed device (27) for feeding hydrogen into the vacuum environment (17), in which at least one silicon-containing surface (29a) is arranged. The feed device (27) additionally feeds an oxygen-containing gas into the vacuum environment (17) and has a metering device (28) that sets an oxygen partial pressure (pO2) at the at least one silicon-containing surface (29a) and/or at the optical surface (13a, 14a).