Process for improving the cold start behaviour of selective CO-oxidation catalysts

Process for improving the cold start behavior of selective carbon monoxide oxidation catalysts in gas purification stages of a gas generating system comprises feeding a medium stream over the oxidation catalyst after switching off the gas generating system to flush out start-delaying components. Preferred Features: The medium stream contains oxygen. The medium stream is fed over the catalyst before the catalyst is cooled. The medium stream is fed around an anode chamber of a fuel cell via a by-pass after it has been fed over the catalyst.