Deck General · Extinguishing Agents
CO2 extinguishes fire primarily by which mechanism?
- ACooling the fuel below its ignition point
- BChemically inhibiting the combustion chain reaction
- CDisplacing oxygen and smothering the fire✓ Correct
- DForming a foam blanket over the surface of burning liquid
Explanation
Carbon dioxide extinguishes by smothering — it dilutes and displaces the oxygen in the air around the fire until the O2 concentration drops below approximately 15%, at which point combustion cannot continue. It also provides minor cooling. CO2 leaves no residue, making it ideal for electrical equipment and machinery spaces, but it cannot be used in occupied spaces without evacuating personnel first.
Authority: Firefighting (USCG deck topic)
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