Reactive Chlorine Emissions from Cleaning and Reactive Nitrogen Chemistry in an Indoor Athletic Facility

Indoor gas-phase radical sources are poorly understood but expected to be much different from outdoors. Several potential radical sources were measured in a windowless, light-emitting diode (LED)-lit room in a college athletic facility over a 2 week period. Alternating measurements between the room air and the supply air of the heating, ventilation, and air-conditioning system allowed an assessment of sources. Use of a chlorine-based cleaner was a source of several photolabile reactive chlorine compounds, including ClNO₂ and Cl₂. During cleaning events, photolysis rates for these two compounds were up to 0.0023 pptv min^-1, acting as a source of chlorine atoms even in this low-light indoor environment. Unrelated to cleaning events, elevated ClNO₂ was often observed during daytime and lost to ventilation. The nitrate radical (NO₃), which is rapidly photolyzed outdoors during daytime, may persist in low-light indoor environments. With negligible photolysis, loss rates of NO₃ indoors were dominated by bimolecular reactions. At times with high NO₂ and O₃ ventilated from outdoors, N₂O₅ was observed. Elevated ClNO₂ measured concurrently suggests the formation through heterogeneous reactions, acting as an additional source of reactive chlorine within the athletic facility and outdoors.