Vapor Space Flammability of Automobile Tanks Containing Low RVP Gasolines

This book reports that, as a means of reducing evaporative emissions from gasoline sources, the Environmental Protection Agency (EPA) and other legislative and regulatory bodies have required reductions in gasoline volatility. Further reduction are being proposed. This paper reports the results of an investigation into the resulting flammability potential of low volatility gasolines contained in automobile tanks when low ambient temperatures are experienced. The hydrocarbon composition and the flammability tendency of the vapor in fuel tanks of passenger cars were determined via a matrix of 45 different gasoline volatility, temperature, and tank level combinations. A flammability device was developed and used to ignite vapors drawn from the tanks of in-use vehicles at the test conditions. The Reid Vapor Pressure (RVP) of the test gasolines ranged from 6.5 to 9.4 psi in the near-full tank level and 6.4 to 7.8 psi at a low tank level. Ambient test temperatures were selected to represent probable winter/spring and fall/winter transition period low temperatures. Results demonstrate that at moderately low temperatures and low gasoline volatility conditions, the vapor space of a vehicle's fuel tank will be flammable and no longer protected by the volatile components in the fuel. Such a condition will result inmore » a flame if an ignition source is available. It was demonstrated that an initial fill of 9.4 psi RVP gasoline does not result in a flammable vapor space at temperatures above 0{degrees}F. However, upon drive-down to a low tank level, the same gasoline produced a fully flammable vapor space at 0{degrees}F and even a marginally flammable vapor space at 10{degrees}F. A simple model was developed to predict fuel tank hydrocarbon vapor concentrations as a function of the gasoline RVP and operating temperature.« less