46 CFR § 30.10-22 - Flammable liquid - TB/ALL.
The term flammable liquid means any liquid which gives off flammable vapors (as determined by flashpoint from an open-cup tester, as used for test of burning oils) at or below a temperature of 80 °F. Flammable liquids are referred to by grades as follows:
(a) Grade A. Any flammable liquid having a Reid 1 vapor pressure of 14 pounds or more.
1 American Society for Testing Materials Standard D 323 (incorporated by reference, see § 30.01-3), Method of Test for Vapor Pressure of Petroleum Products (Reid Method).
(b) Grade B. Any flammable liquid having a Reid 1 vapor pressure under 14 pounds and over 8 1/2 pounds.