INTRODUCTION CONTRACT BACKGROUND The automobile has long been recognized as a major source of the hydrocarbons in the air over our cities. Emissions of hydrocarbons from automobiles arise primarily from incomplete burning of gasoline with in the engine's combustion chamber@ from the escape of combustion gases which blow by the piston rings and from evaporation of gasoline from the vehicle's fuel system. While accurate figures are not available@ a typical automobile with no emission control devices will emit about 500 pounds of hydrocarbons a year. Approximately 60% of this weight is emitted in the exhaust gases@ 25% as blowby and 15% as evaporative emissions. Emission control devices which are presently required on all new automobiles sold in the United States result in substantial reduction s in exhaust gas and blowby hydrocarbons. Proposed future control of vehicle evaporation losses should result in meaningful reductions in hydrocarbon losses from this source. One area of vehicle losses which has received little attention is that of passenger car refueling losses. These losses include: 1. Displaced fuel tank vapors 2. Entrained fuel droplets in the displaced vapors 3. Liquid spillage 4. Nozzle drippage On March 26@ 1969@ Scott Research Laboratories@ Inc.@ was awarded a contract by the Coordinating Research Council@ Inc.@ and the Department of Health@ Education and Welfare to conduct a Study of Passenger Car Refueling Losses. The general objective of this program was to investigate the magnitude and frequency of hydrocarbon losses due to refueling of typical passenger cars. The specific objectives are listed below: ? Measure hydrocarbon losses from splash and subsurface filling@ tank spillage and nozzle drip. ? Gather data relative to frequency of hydrocarbon losses above. ? Classify data according to fuel tank configuration and calculate probability of various losses for each configuration.