Near-source hypochlorous acid emissions from indoor bleach cleaning

Cleaning surfaces with sodium hypochlorite (NaOCl) bleach can lead to high levels of gaseous chlorine (Cl₂) and hypochlorous acid (HOCl); these have high oxidative capacities and are linked to respiratory issues. We developed a novel spectral analysis procedure for a cavity ring-down spectroscopy (CRDS) hydrogen peroxide (H₂O₂) analyzer to enable time-resolved (3 s) HOCl quantification. We measured HOCl levels in a residential bathroom while disinfecting a bathtub and sink, with a focus on spatial and temporal trends to improve our understanding of exposure risks during bleach use. Very high (>10 ppmv) HOCl levels were detected near the bathtub, with lower levels detected further away. Hypochlorous acid concentrations plateaued in the room at a level that depended on distance from the bathtub. This steady-state concentration was maintained until the product was removed by rinsing. Mobile experiments with the analyzer inlet secured to the researcher's face were conducted to mimic potential human exposure to bleach emissions. The findings from mobile experiments were consistent with the spatial and temporal trends observed in the experiments with fixed inlet locations. This work provides insight on effective strategies to reduce exposure risk to emissions from bleach and other cleaning products.