Bedroom Concentrations and Emissions of Volatile Organic Compounds during Sleep

Abstract

Because humans spend about one-third of their time asleep in their bedrooms and are themselves emission sources of volatile organic compounds (VOCs), it is important to specifically characterize the composition of the bedroom air that they experience during sleep. This work uses real-time indoor and outdoor measurements of volatile organic compounds (VOCs) to examine concentration enhancements in bedroom air during sleep and to calculate VOC emission rates associated with sleeping occupants. Gaseous VOCs were measured with proton-transfer reaction time-of-flight mass spectrometry during a multiweek residential monitoring campaign under normal occupancy conditions. Results indicate high emissions of nearly 100 VOCs and other species in the bedroom during sleeping periods as compared to the levels in other rooms of the same residence. Air change rates for the bedroom and, correspondingly, emission rates of sleeping-associated VOCs were determined for two bounding conditions: (1) air exchange between the bedroom and outdoors only and (2) air exchange between the bedroom and other indoor spaces only (as represented by measurements in the kitchen). VOCs from skin oil oxidation and personal care products were present, revealing that many emission pathways can be important occupant-associated emission factors affecting bedroom air composition in addition to direct emissions from building materials and furnishings.

Volatile Organic Compound Composition and Emissions in a Residential Attic

“…As a starting point for testing whether the findings at H3 apply elsewhere, data from three additional residential indoor air studies in northern California (House 1 Summer/Winter (H1 S/W) and House 2 Winter (H2 W)) were compared to H3 results. H1 was constructed in the late 1930s, H2 was constructed in the early 1950s, and H3 was constructed in 1910 Table S6 summarizes the correlations and slopes with respect to furfural of the 40 analyzed species in H3 for all four field campaigns.…”

“…A proton-transfer-reaction time-of-flight mass spectrometer (PTR-TOF-MS 8000 (Ionicon Analytik); authors refer to this instrument only as the “PTR-TOF-MS” throughout the remainder of the paper) measured VOCs at six locations, including the attic, living room, kitchen, lower-level room, garage, and outdoors. Sample lines were made of polytetrafluoroethylene (PTFE) and were ∼23 m in length . Any time lag in VOC signal from the instrument during sampling due to the length of the sample lines was corrected in the postprocessing steps of the data.…”

“…Occupants recorded their activities and presence throughout the campaign. More details are reported in Molinier et al, and the house layout is summarized here. H3 has three levels: (1) the attic is the top level; (2) most of the living zone, including the kitchen, living room, and main bedroom comprise the middle level; and (3), the basement/garage and lower living level make up the bottom level.…”

“…These calibrations were used to obtain sensitivity factors to convert the ion signals in counts per second to ppb; a default sensitivity factor was applied to compounds not directly calibrated, which can result in higher uncertainty . More details on instrumentation and data processing can be found in Molinier et al…”