Commercial kitchen operations produce a diverse range of gas-phase reactive nitrogen species.

Gas-phase reactive nitrogen species (N) are important drivers of indoor air quality. Cooking and cleaning are significant direct sources indoors, whose emissions will vary depending on activity and materials used. Commercial kitchens experience regular high volumes of both cooking and cleaning, making them ideal study locations for exploring emission factors from these sources. Here, we present a total N (tN) budget and contributions of key species NO, NO, acidic N (primarily HONO) and basic N (primarily NH) using novel instrumentation in a commercial kitchen over a two-week period. In general, highest tN was observed in the morning and driven compositionally by NO, indicative of cooking events in the kitchen. The observed HONO and basic N levels were unexpectedly stable throughout the day, despite the dynamic and high air change rate in the kitchen. After summing the measured NO, HONO and N fractions, there was on average 5 ppbv of N unaccounted for, expected to be dominated by neutral N species. Using co-located measurements from a proton transfer reaction mass spectrometer (PTR-MS), we propose the identities for these major N species from cooking and cleaning that contributed to N and the neutral fraction of tN. When focused specifically on cooking events in the kitchen, a vast array of N-containing species was observed by the PTR-MS. Reproducibly, oxygenated N-containing class ions (CHON), consistent with the known formulae of amides, were observed during meat cooking and may be good cooking tracers. During cleaning, an unexpectedly high level of chloramines was observed, with monochloramine dominating the profile, as emitted directly from HOCl based cleaners or through surface reactions with reduced-N species. For many species within the tN budget, including HONO, acetonitrile and basic N species, we observed stable levels day and night despite the high air change rate during the day (>27 h). The stable levels for these species point to large surface reservoirs which act as a significant indoor source, that will be transported outdoors with ventilation.