In the event of a Class K fire, the agent forms a protective layer by:

• A. Forming a dry powder crust
• B. Saponifying fats to create a soapy layer
• C. Absorbing water and evaporating
• D. Smothering with foam

Answer: (B)

Class K fires involve cooking fats and oils, and the extinguishing agent used for these fires works through a fat-saponification reaction. When the wet chemical agent is applied, it reacts with the fatty oils to form potassium soaps, creating a soapy, viscous layer on the surface of the fat. This soapy layer coats and cools the oil and acts as a barrier between the fuel and the air, helping to smother the fire and prevent reignition. The other mechanisms listed don’t produce this protective fat-soap layer: a dry powder crust is for metal fires, absorbing water and evaporating won’t form the necessary barrier for fats, and foam smothers by separation of fuel and air but not through fat saponification.