Chemistry and Chemical Disasters. A liquid having a flash point below 100oF (37.8oC) and having a vapor pressure not exceeding 40 lbs per square inch absolute (276 kilopascals) at 100oF (38.8oC). Flammable (Class I) liquids are subdivided into Classes IA, IB, and IC. Refer to NFPA No. 30 for further details. (RP 500B)