Human bioeffluents can significantly alter the composition of indoor air in occupied spaces. As humans spend ~90% of their time indoors, bioeffluent exposures might influence personal health. Transport of bioeffluents from indoors to outdoors might also influence atmospheric oxidation processes in the troposphere. It is therefore valuable to make in-situ measurements of bioeffluent concentrations and to quantify associated whole-body emission factors indoors. We pursued this goal as part of the H3 measurement campaign, which was conducted in a single-family residence in Oakland, California, with sampling occurring over approximately ten weeks, starting in October 2021. We deployed a proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS) to measure VOC concentrations at six locations. The instrument sampled from each location in sequence, switching every five minutes, and thus completing two full cycles every hour. We also deployed an LI-820 CO₂ analyzer and a ThermoScientific 49i ozone analyzer to collect CO₂ and O₃ data, respectively, using the same sampling scheme. Throughout the course of the campaign, over 200 VOCs were detected at concentrations above a reporting limit of five parts per trillion, including several known breath and skin bioeffluents. We dedicated several weeks of this campaign to sampling VOC concentrations in the main bedroom of the residence to investigate human emissions to the indoor environment during sleeping periods. As expected, the nighttime bedroom data show high accumulation of CO₂, acetone, and isoprene, the three most abundant bioeffluents. Correlation values over ten nights of isoprene and acetone with respect to CO₂ were R² = 0.95 and 0.90, respectively. Using literature values for human CO₂ emission rates, nightly bedroom air change rates were estimated to then determine average whole-body emission factors for isoprene and acetone, which were 0.74 and 12.9 mg h^-1 p^-1, respectively. Emission factors for other bioeffluents, such as furan and acetamide, were also calculated.

Betty Molinier

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