Indoor Gas-Phase Chemistry

Abstract

There are many similarities between indoor and outdoor air chemistry, not least the richness of the oxidation chemistry. Indoors, oxidation is driven to a large extent by ozone and the hydroxyl radical, with nitrate and chlorine radicals also making a contribution depending on the conditions. These reactions can lead to a variety of products, many of which are multifunctional and relatively long-lived. Some of them can then take part in further reactions indoors. This chapter summarizes the main gas-phase reactions indoors and also highlights the interconnectedness between some of the oxidation reactions, particularly between ozone and the hydroxyl radical. Oxidation of common indoor species such as monoterpenes by ozone leads to the formation of hydroxyl and peroxy radicals. There is then a range of radical-radical reactions possible that further transform the gas-phase composition indoors. Oxidation of terpenes and other volatile organic compounds by the hydroxyl radical can also produce ozone if there is sufficient light indoors, so that these two oxidants are likely to coexist for many conditions typically experienced in buildings.