1. Introduction Tropospheric ozone is a key component of air pollution (e.g. [1]). It is formed through a complex series of photochemical reactions that involve cycles which couple the nitrogen oxides (NOx = NO + NO2) and hydrogen oxides (HOx = OH + HO2) and is mediated by volatile organic compounds (VOCs). The most basic mechanism, where carbon monoxide (CO) represents a VOC, is outlined below CO+OH(+O2)→CO2+HO2HO2+NO→NO2+OHNO2+hv→NO+O(3P)O(3P)+O2+M→O3+MMechanism 1.