Semivolatile organic compounds (SVOCs) represent a diverse and dynamic class of chemicals found indoors with poorly understood temporal behavior. Past analytical work has incorporated time-averaged sampling procedures, limiting the scope of inquiries about SVOCs in indoor air. Thermal desorption aerosol gas chromatography (SV-TAG) is an established analytical technique for measuring SVOCs in the gas- and particle-phases with hourly time resolution. In this study, SV-TAG was used to measure the indoor distribution of SVOCs in an occupied California home over a two-month period. Data reveal dynamic and persistent ranges of individual chemicals and chemical classes, including phthalates. The effects of physical parameters and occupant behavior on airborne phthalate concentrations and other SVOCs of interest were explored. Phthalate levels were roughly five times higher indoors than outdoors. Occupant behavior had no clear effect on total phthalate emissions, which were dominated by the contents of the house and strongly modulated by temperature.

Residences are important sites of daily bioaerosol exposure; yet the relative contributions of outdoor and indoor sources are not well-understood. Biological particles can be detected using laser-induced fluorescence. Applying real-time instrumentation, this work investigated the contributions of indoor and outdoor sources to fluorescent aerosol particle exposures in a northern California residence with three human residents and a dog. Time- and size-resolved total and fluorescent particle concentrations were measured indoors and outdoors, using an ultraviolet aerodynamic particle sizer (UVAPS) and a switching valve. Time-resolved occupancy status and household activities, such as cooking and cleaning, were obtained using occupant-maintained logs and wireless electronic sensors. Our observations show the indoor to outdoor ratio of fluorescent particles is strongly influenced by occupancy, and that indoor sources contribute a considerable fraction of total daily fluorescent particle exposures at home. This work will improve understanding of the relationship between human activities and bioaerosol exposure in residences.

Human-emitted volatile organic compounds and other trace gases often dominate concentrations of occupied indoor atmospheres. With the application of real-time mass spectrometry, it has become possible to measure time-resolved behaviour of breath metabolites, skin emanations including oil oxidation products and microbial VOCs, and other bioeffluents. The temporal and mass spectral resolution enables deeper understanding of their impact on air quality, VOC exposure, and sensory perceptions. Per-person CO2 and VOC emissions derived from similar groups of students indicate consistencies in major breath metabolites. Skin-emitted VOCs can be differentiated from volatilization of consumer care products by their distinctive diurnal patterns. Here we synthesize recent approaches to time-resolved measurements of human bioeffluents by PTRMS to inspire new research directions in indoor air science.

This study provides novel observations and insight into the chemical composition of indoor air. Utilizing state-of-the-art semi-volatile thermal-desorption aerosol gas chromatography (SV-TAG) we present, for the first time, hourly concentrations and partitioning of semivolatile organic compounds (SVOC) measured in a single-family house in California during normal occupancy. Time series of indoor SVOCs were characterized by temperature-dependent elevated background levels for a broad suite of chemicals, underlining the importance of continuous emissions from static indoor sources, i.e. building materials and interior contents. However, the highest SVOC concentrations were observed during episodic enhancements associated with occupant activities.

Knowledge of human exposures to volatile organic compounds (VOCs) is critical for understanding their impact on human health. We measured time-resolved concentrations in combination with collecting occupancy data for a wide range of VOCs in two residences in northern California. We report exposures to hundreds of volatile organic compounds present indoors, spanning orders of magnitude in abundance, toxicity and reactivity. We show that concentrations of most VOCs were considerably higher indoors than outdoors, with the sum of measured VOCs being of an order of magnitude higher, in each season and each residence. Occupant's activities were the largest source of short-term episodic exposures, while VOCs from wood degradation were prominent contributors to chronic exposures. We show a comprehensive account of known and newly observed air toxics, their sources, and quantify time-resolved and daily-integrated exposures. We found that daily-integrated measurements could underestimate total exposure to VOCs and point to the need for time-resolved concentration measurements to accurately assess exposures.