When putting out a fire involving oily rages, use a ____ fire extinguisher

• A. Class A
• B. Class C
• C. Class D
• D. Class B

Answer: (D)

Fires involving flammable liquids require a Class B extinguisher. Oily rags burn because they release flammable vapors from the oil, so the extinguisher must be designed to blanket and smother liquid fuels rather than burnables or electrical fires. Class B extinguishers, using dry chemical or foam, interrupt the flame and separate the fuel from the oxygen, helping to prevent reignition. Water should not be used on oil fires because oil and water don’t mix and water can spread burning oil. The other extinguisher types correspond to different fire scenarios—ordinary combustibles, electrical equipment, or combustible metals—and wouldn’t be effective for an oily rag fire.