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44Oxymoronic equationGround-level ozone is produced by chemical reactions between oxides of nitrogen (NOx) and volatile organic compounds (VOCs) under sunlight. NOx are mostly produced during the combustion of nitrogen compounds in fuel, such as emissions from cars, power plants and refineries. Over 100 different kinds of VOCs can be produced by biogenic sources such as plants, as well as by anthropogenic sources such as fuel production and combustion. Their reaction can be summarised as:From this equation, we may expect that higher concentrations of NOx and VOCs in the air lead to higher concentrations of ozone. However, this is not always what happens, and the research team wanted to know why this was the case. Prof. Wang and Prof. Guo thus separately developed the first Hok Tsui air monitoring supersiteNOx VOCsSunlightTAKE A DEEP BREATHOzone