Which of the following best confirms suitability of a Class K extinguisher for cooking fats and oils?

• A. The extinguisher carries a Class A rating
• B. The label specifies Class K and a compatible wet chemical agent
• C. The extinguisher is the heaviest option
• D. The extinguisher uses water as the agent

Answer: (B)

Cooking grease fires require a specialized extinguisher designed for fats and oils. A Class K extinguisher is purpose-built for these fires, using a wet chemical agent that reacts with fats to form a soapy, viscous layer on the surface. This saponified layer cools the oil, smothers the flame, and helps prevent re-ignition by sealing the fuel from air and inhibiting heat transfer. Seeing a label that specifies Class K and a compatible wet chemical agent confirms it will work effectively on cooking fats and oils and is suitable for kitchen environments.

An extinguisher labeled only for Class A targets ordinary combustibles like wood and paper, not fats and oils, so it isn’t the right tool for grease fires. The weight of the extinguisher doesn’t indicate suitability for this fire type, and water-based agents are unsafe for oil fires because oil and water don’t mix; water can splatter, spread the burning oil, and cause dangerous steam and flare-ups instead of cooling and smothering the fire.