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

Abstract

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 ClNO 2 and Cl 2 . 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 ClNO 2 was often observed during daytime and lost to ventilation. The nitrate radical (NO 3 ), which is rapidly photolyzed outdoors during daytime, may persist in low-light indoor environments. With negligible photolysis, loss rates of NO 3 indoors were dominated by bimolecular reactions. At times with high NO 2 and O 3 ventilated from outdoors, N 2 O 5 was observed. Elevated ClNO 2 measured concurrently suggests the formation through heterogeneous reactions, acting as an additional source of reactive chlorine within the athletic facility and outdoors.

Elevated levels of chloramines and chlorine detected near an indoor sports complex

“…The outdoor observations in the current work point to cleaning activities/emissions in an indoor sports complex as a persistent point source for gaseous Cl-containing compounds outdoors. This closes the loop with previous work that suggested these molecules can be effectively removed from indoor environments with sufficient AER, 6,16 and our observations confirm that they reach the outdoor atmosphere. Previous measurements in Leicester observed median levels of 15.4 and 139 pptv for ClNO 2 , with maxima of 74.2 and 733 pptv during 2014 and 2016, respectively, 42 comparable to NH 2 Cl levels presented in the current work (Table 1).…”

“…Therefore, both locations are potential sources of the observed NH 2 Cl and Cl 2 , based on prior reports of these molecules from their use indoors. 6,[14][15][16]47 Cooling towers and water treatment facilities are potential sources of chloramines outdoors, 32 and treated water contains chloramines that can partition into the air when converted to a ne mist. However, there are no such towers or facilities nearby the sampling site that could contribute to our observed levels of NH 2 Cl and our ambient data provide no indication that said phenomena were observed.…”

“…Reservoir species for the Cl atom are increasingly being recognized as important to atmospheric oxidative budgets and are prevalent in both indoor and outdoor atmospheres. [1][2][3][4][5][6] The formation and fate of atmospheric chloramines (NH x Cl y ), which include monochloramine (NH 2 Cl), dichloramine (NHCl 2 ), and trichloramine (NCl 3 ) are not yet well-described, but substantial knowledge on their formation in aqueous media has been described. Major chemical or direct sources of chloramines to the outdoor atmosphere are not known.…”

“…Taken together, indoor environments with elevated AER are likely direct sources of reactive chlorine species (i.e., Cl*) to the outdoor atmosphere. 6,10,[12][13][14][15][16] The need for high AER is because elevated levels of gas-phase chloramines in indoor areas are a health concern, with exposure linked to eye irritation, rashes, and respiratory difficulty. 17 The World Health Organization (WHO) recommends levels of gaseous chloramines (measured as NCl 3 ) to be below 90 ppbv; while a study by Parrat et al argues that this limit should be 60 ppbv.…”

“…14 Indoor measurements of chloramines during bleach cleaning activities have estimated upper limits on the mixing ratios of NH 2 Cl, NHCl 2, and NCl 3 to be 60, 0.5, and 6.8 ppbv, respectively. 15 Finewax et al 16 and Moravek et al 6 observed increased concentrations of chloramines, HOCl, ClNO 2 , and Cl 2 after a solution of dichloro- s -triazinetrione (dichlor) was used to clean an indoor weight room. Increases in these species were attributed to reactions involving HOCl on the surfaces – where the solution was applied using charged droplets – as opposed to direct emissions from the application of spray solution.…”