For the 2021 edition of NFPA 30, the committee introduced a sweeping change in the classification scheme for liquids. The term ignitible liquid has been introduced to initiate a process whereby the terms flammable liquid and combustible liquid are no longer used. This causes the requirements in NFPA 30 and other codes and standards to adopt a scheme based exclusively on the liquid physical state and property (i.e., the liquid flash point), for all liquids that can be ignited. The necessity for this change stems from the existence of multiple regulatory systems that use the terms flammable liquid and combustible liquid inconsistently, leading to confusion in how to apply regulations properly among overlapping regulatory authorities, such as fire officials, occupational safety officials, and transportation officials.
The term ignitible liquid is used to include all liquids with a measurable flash point. To assist existing code users in the transition, the terms flammable liquid and combustible liquid have been retained in a diminished capacity. Unless otherwise specified, the term liquid means ignitible liquid.
As a result of the change in approach for classifying liquids, the committee determined that Chapter 4 was actually not for defining the liquid classification, but instead for establishing the classification scheme based on the introduced flash point and boiling point criteria. The revisions to Chapter 4 address the classification criteria, whereas Chapter 3 defines specific liquids. The revisions to Chapters 1, 3, and 4 seek to make the requirements consistent with each other in terms of the scope of the code, specific terminology, and the evaluation of liquids within the classification scheme. The revised classification scheme outlined in Chapter 4 has been implemented throughout the code and annexes.