Reid vapor pressure

Reid vapor pressure (RVP) is a common measure of the volatility of gasoline. It is defined as the absolute vapor pressure exerted by a liquid at 100 °F (37.8 °C) as determined by the test method ASTM-D-323. The test method applies to vapor pressure of gasoline, volatile crude oil, and other volatile petroleum products, except liquefied petroleum gases. RVP is stated in units of psi but would be more correct to be stated as psig as ASTM-D-323 is measuring the gauge pressure of the sample in a non-evacuated chamber.