Class K extinguishers are intended for which type of fire?

• A. Wood and paper
• B. Commercial kitchen oil and fat fires using wet chemical agents
• C. Electrical fires
• D. Metal fires

Answer: (B)

Class K extinguishers are designed for fires that involve cooking oils and fats, which you typically find in commercial kitchens. They use a wet chemical agent (often potassium acetate) that saponifies fats—that means it turns the oil into a soapy layer. This soapy layer cools the oil, creates a barrier between the fuel and the air, and helps prevent reignition. This specialized action makes them the best choice for fires from cooking oils and fats. Other fire types have different extinguishing needs: wood and paper fires are ordinary combustibles (Class A), electrical fires require nonconductive or energized-safe methods (often Class C or a listed electrical-rated extinguisher), and metal fires require unique dry powders (Class D). The wet chemical approach of Class K is specifically tailored to the chemistry of cooking-oil fires, which is why it’s the correct fit here.