Migration of volatile organic compounds from attached garages to residences: a major exposure source.

Vehicle garages often contain high concentrations of volatile organic compounds (VOCs) that may migrate into adjoining residences. This study characterizes VOC concentrations, exposures, airflows, and source apportionments in 15 single-family houses with attached garages in southeast Michigan. Fieldwork included inspections to determine possible VOC sources, deployment of perfluorocarbon tracer (PFT) sources in garages and occupied spaces, and measurements of PFT, VOC, and CO(2) concentrations over a 4-day period. Air exchange rates (AERs) averaged 0.43+/-0.37 h(-1) in the houses and 0.77+/-0.51 h(-1) in the garages, and air flows from garages to houses averaged 6.5+/-5.3% of the houses' overall air exchange. A total of 39 VOC species were detected indoors, 36 in the garage, and 20 in ambient air. Garages showed high levels of gasoline-related VOCs, e.g., benzene averaged 37+/-39 microg m(-3). Garage/indoor ratios and multizone IAQ models show that nearly all of the benzene and most of the fuel-related aromatics in the houses resulted from garage sources, confirming earlier reports that suggested the importance of attached garages. Moreover, doses of VOCs such as benzene experienced by non-smoking individuals living in houses with attached garages are dominated by emissions in garages, a result of exposures occurring in both garage and house microenvironments. All of this strongly suggests the need to better control VOC emissions in garages and contaminant migration through the garage-house interface.