When mixed with air, nitric oxide plays a key role in the generation of smog, ozone and other pollutants. Gold, when deposited with metal oxides in monitoring devices, spurs a remarkable increase in the efficiency of converting carbon monoxide to carbon dioxide. Gold particles, when coated over aluminum oxide, promote a 40-percent increase in the conversion of nitric oxide to harmless nitrogen. Field tests for their use in gas masks for firefighters and coal miners, and in carbon monoxide gas sensors also has begun. Gold's properties, especially its non-reactivity, are integral in the catalytic process to control air pollutants.
Gold has advantages over other commercial catalysts.
For example, oxides of copper and manganese do not work well in a moist environment and other precious metals, while moisture tolerant, are less effective as a catalyst at low temperatures. With gold, however, the catalytic activity is enhanced by water vapor and is efficient at room temperatures. However, water-based paints dry differently, and automakers found that drying ovens plated with gold ensured the new paints provided the same quality finish as did their predecessors. Automotive paint drying ovens use infrared heat energy to dry auto paints. The combination of the infrared energy and gold reflectivity works more efficiently in drying water-based paints, saving time and lowering the energy use.