The changes in the surface areas of copper and zinc oxide have been measured to evaluate the individual rates of sulfur coverage of each of these phases during catalyst exposure to sulfur‐containing gas. Zinc oxide surface areas have been measured by CO2 adsorption and copper surface areas by measurement of the nitrogen formed by exposure to nitrous oxide. The surface areas of both components decreased exponentially with increasing exposure time to the sulfur‐containing gas. The zinc oxide component is more sulfur‐resistant than copper. This is attributed to either kinetic limitation or the more stable surface sulfides of zinc.