Deck General · Extinguishing Agents
Dry chemical extinguishing agents (ABC dry chem) are most effective against Class B fires because they:
- ACool the burning liquid below its flashpoint
- BInterrupt the chemical chain reaction of combustion✓ Correct
- CForm a water vapor barrier around flammable vapors
- DBond chemically with fuel molecules to render them non-flammable
Explanation
Dry chemical agents (monoammonium phosphate for ABC, sodium bicarbonate for BC) work primarily by chemically interrupting the uninhibited chain reaction of the fire tetrahedron. This is why they are extremely fast-acting on Class B (liquid) and Class C (electrical) fires. The powder cloud also has a minor smothering effect, but chain-reaction interruption is the dominant mechanism.
Authority: Firefighting (USCG deck topic)
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