Definition and classification of flammable and combustible liquids are addressed in
Subsection 3.3.33 and Chapter 4 of NFPA 30. A flammable liquid is defined as a liquid
whose flash point does not exceed 100°F, when tested by closed‐cup test methods,
while a combustible liquid is one whose flash point is 100°F or higher, also when tested
by closed‐cup methods. These broad groups are further classified as follows: