Method and apparatus for measuring evaporative vehicle emissions in a

Abstract

Provided is a method and apparatus for measuring evaporative vehicle emissions in a fixed-volume/variable temperature test chamber. The method comprises the steps of providing a volume compensation device in fluid communication with a test chamber for compensating for changes in the test chamber fluid volume, determining the density of the evaporative emissions and the test chamber fluid in mass per unit volume at selected sample times t.sub.n, where n is a positive integer, measuring the temperature of the test chamber fluid at the sample times t.sub.n, measuring the absolute fluid pressure of fluid at the sample times t.sub.n, determining the difference in the test chamber fluid volume between successive sample times t.sub.n, determining the mass of the evaporative emissions in lost volume and mass measurements and summing the determined masses of the evaporative emissions to provide a calculation of the evaporative emissions lost by the volume compensation device during expansion of the test chamber fluid and summing this with the final sample to determine the total evaporative emissions from a vehicle. In an alternative embodiment, a plurality of impingers are also provided for use in determining the lost mass of alcohol emissions in flexible fueled vehicles.