What is the mechanism of action of Class K extinguishing agents on cooking oils?

• A. Wet chemical saponification of fats.
• B. Foam that forms a film over the fire.
• C. Dry chemical that interrupts the chemical chain reaction.
• D. Water application to cool the fuel.

Answer: (A)

Cooking-oil fires respond best to a wet chemical action that saponifies fats. The wet chemical agent, typically potassium acetate, reacts with triglycerides in the oil to form glycerol and potassium fatty acid salts—soap. This soap then forms a stable, soapy layer that spreads across the oil surface, emulsifying the fat and creating a barrier between the fuel and the flame. That layer smothers the fire by limiting oxygen contact and vapor release, and it helps prevent re-ignition by keeping the oil from feeding the flame. This mechanism is different from simply forming a foam blanket or from dry chemical powders that interrupt flame chemistry, and it avoids using water, which can cause splashing and spreading of burning oil.