The isotopic composition of CO in vehicle exhaust

A set of polluted atmospheric samples, taken near a highway and inside parking garages, showed an isotopic signature of CO and a H2:CO ratio that were similar the high emitters in the individual vehicle measurements, with no significant differences between parking garage and highway samples. This suggests that in both environments, which are dominated by different driving conditions, the CO emissions from high emitters (either a few high emission vehicles, or many vehicles with brief bursts of high emissions) dominate the total traffic emissions.