Formation and emission of reactive chlorine in indoor air

Dawe, Kathryn E. R. (2018) Formation and emission of reactive chlorine in indoor air. Masters thesis, Memorial University of Newfoundland.

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Abstract

Chlorine atoms are powerful atmospheric oxidants known to degrade air quality. Despite much focus, a direct measurement technique does not exist. Instead, chlorine atom precursors are used as proxies to study chlorine atom chemistry. Reactions of precursors resulting in chlorine atoms studied in outdoor environments are also possible indoors. Daily household activities, especially those involving chlorinated cleaning products, are suspected to contribute to indoor chlorine atom chemistry. Indoor air studies are hindered by sampling techniques, as few appropriate instruments exist. A common atmospheric measurement technique was evaluated while monitoring gas and particulate phase species emitted during indoor bleach use. This instrument collects a non-selective gaseous and a particulate chloride sample. Recent advances in indoor instrumentation allow for selective measurement of chlorine atom precursor, hydrogen chloride (HCl), using a cavity-ring down spectroscopy instrument. Present ubiquitously outdoors, atmospheric HCl is a result of direct emission and secondary production. Previous measurements of HCl indoors are rare and have been limited to non-residential buildings using integrated sampling. This sampling strategy does not provide the source of HCl emissions. In order to better understand sources of HCl indoors, real-time gas-phase mixing ratios of HCl during typical household activities were monitored such as floor exposure to bleach, detergent use in household dishwashers, and cooking events. Based on calculated rates of chlorine atom precursors, both photolysis and direct emission could be contributing to elevated HCl levels indoors. This work presents insights regarding HCl production and the influence of household activities on indoor air quality.

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