Foam Agents and AFFF System Design Considerations

Foams have been developed almost entirely from experimental work. Although the technologies are rather mature, no fundamental explanations of foam extinguishment performance have been developed based on first principles. As a result, foams are characterized by (1) fire tests for which there is no general international agreement and (2) physical and chemical properties that may or may not correlate with empirical results. This chapter reviews the important parameters associated with foam agents, test methods used to evaluate foams, and relevant data in the literature that can be used to evaluate foam system designs. Because of their superior performance in extinguishing certain types of hydrocarbon liquid fuel fires, the emphasis is on film-forming foams and thin pool fires (e.g., from spills). Situations involving fuels “in depth” are limited to a discussion on foam modeling and small-scale tests to assess oil and petrochemical industry hazards.