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The concentration of gasoline vapors was measured in the breathing zone of a person. refueling automobiles in both summer and winter. The concentrations of total hydrocarbons ranged from 5 to 1220 ppmC in summer and from 4 to 3210 ppmC in winter. Individual values were affected by wind speed and direction, as well as by body shielding caused by the refueler. Compared to the dispensed gasoline, the refueling vapors were enriched in hydrocarbons with normal boiling points below about 125°F, so that five light paraffins (n-butane, isopentane, iso-butane, n-pentane, and propane) constituted more than 70% of the total carbon in the vapors. The combination of the resulting low concentration of the heavier hydrocarbons in the vapor and the rapid dispersal and dilution of the vapor plume minimizes the brief exposure of refuelers to benzene and the C7, and C8 isoparaffins.