Reactive nitrogen species (Nr), defined here as all N-containing compounds except N2 and N2O, have been shown to be important drivers for indoor air quality. Key species including NOx, HONO and NH3, are known to have detrimental health effects. In addition, other Nr species such as amines that are not traditionally measured may be important chemical actors for indoor transformations. Cooking and cleaning are significant sources, with variable emissions depending on activity type and materials. During the start up of a commercial kitchen - from closure during the pandemic to resuming service for more than 500 meals per day in catering and a la carte orders - we measured the composition of the indoor air with a custom-built instrument to quantify the total gas-phase reactive nitrogen (tNr) budget and also pools within this including: NOx, HONO, and NHx. Supporting VOCUS-PTR-MS measurements allowed identification of important but previously unrecognized indoor Nr, while ventilation data and traditional gas analyzers provided insight into chemical transformations. Logs of kitchen cooking and cleaning activities were used to isolate sources of various species, while ventilation and resuming of kitchen activities provided insight into impact of sustained use of the indoor space on the budget and composition of tNr. The observed budget (on the order of 10s of ppbv) was dominated by NO2 transported indoors (42-47 %), which formed a HONO reservoir (8 %) in addition to one of NHx (22-27 %). Direct emissions were observed to be rapidly removed from the space due in the presence of effective air change rates (ACR) which could reach the order of 30 hr-1 during cooking times due to sensor-equipped kitchen ventilation hoods. As a result, NO (5-10 %) was observed to originate from outdoor air due to the local presence of a substantial point source during the morning, along with O3. During the rest of the day, direct NO emissions in the kitchen were observed likely from gas stove combustion, that were quickly ventilated from the space on the order of minutes. The remaining fraction of the tNr budget (13-18 %) was found to be mostly accounted for by acetonitrile with a small fraction at night (~6 %) yet remaining for chemical description. Implications of the gaseous tNr budget on oxidant levels and association with observations of airborne particle number and mass will be discussed.

Gaseous reactive nitrogen emissions, transformations, and budget in a commercial kitchen

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