Concentrations and emissions of gasoline and other vapors from residential vehicle garages

High concentrations of airborne volatile organic compounds (VOCs) may be present in residential garages due to emissions from vehicles, lawnmowers, storage containers, and many other items stored in the garage. VOC emissions will ultimately be transported into ambient air and, if the garage is attached to a residence or other building, into living spaces. This study reports on VOC concentrations and emissions at 15 residential garages in Michigan that varied in type, size, use and other characteristics. VOCs were measured in garages and in outside air using 4-day passive sampling, thermal desorption, and GC-MS analysis. Effective air exchange rates (AERs) were determined using a perfluorocarbon tracer gas and the constant injection method. A modeling analysis shows the effect of time-varying ventilation. To estimate temporal and spatial variability, concentrations were measured on 7 subsequent occasions at multiple locations in one garage. This garage was well-mixed, and the temporal variation in AERs and concentrations was modest. Across the 15 garages, 36 different VOCs in garage air, and 20 in ambient air, were quantified. Source groups identified and attributed to garage emissions included evaporated gasoline, solvents, paints, oils, and cleaners. Concentrations of gasoline-related VOCs in most garages were high, e.g., benzene levels reached 159 μg m −3 in one garage. TVOC emissions per garage averaged 3.0±4.1 g day −1, and AERs averaged 0.77±0.51 h −1. VOC concentrations and AERs were not strongly correlated to observed house, garage or meteorological factors, but appeared largely dependent on occupant activities (opening of the garage door) and VOC sources present. This study quantifies the importance of attached garages as VOC sources, and the results are significant for understanding and mitigating indoor exposures, and for estimating emissions for source inventory purposes.