An instrument to measure and fractionate the total reactive nitrogen budget

Reactive nitrogen species, defined as all N-containing compounds except N 2 and N 2 O , are expected to impact indoor air chemistry , much like in the outdoor environment . Key reactive nitrogen (N r ) species include HONO, NH 3 and amines , as they are suspected to have detrimental health effects due to their reactive nature, including the formation of nitrosamine products . I n addition to these compounds, there may be other important N r species such as amides that are not traditionally measured that may be important. Understanding the budget and fractional contribution s of various reactive nitrogen species , or chemically similar ones , will aid our understanding of indoor sources and transformations as well as their interactions with outdoor air . Here we describe a novel yet low-cost instrument , that utilises a commercial NOx analyser, for quantifying the total Nr compound budget as well as selected key species, such as NOx, HONO and NH 3 . We will present proof-of-concept measurements from differ ent indoor environments, such as unoccupied university buildings as well as residential homes, demonstrating the instrument ability to determine the total Nr budget and contrast these against the composition of outdoor air . Furthermore, the contributions from key Nr species such as HONO and NH 3 will be explored in the context of understanding their sources.