Fires involving flammable liquids, greases, and gases are which class?

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

Answer: (B)

Fires are categorized by the type of fuel involved; when the fuel is a flammable liquid or a gas, the hazard is classified as Class B. This grouping reflects that these fuels vaporize and form ignitable mixtures with air, burning readily and often spreading quickly. Knowing it’s Class B guides the suppression approach: foam, dry chemical, or CO2 can be effective by smothering or interrupting the flame, while water is usually avoided because it can spread the liquid or cause vaporization. For contrast, Class A covers ordinary combustibles like wood and paper, Class C involves energized electrical equipment, and Class D covers combustible metals. (Note: in kitchens, cooking oils are sometimes designated as Class K in modern codes, but greases and other flammable liquids are commonly treated as Class B in many exam contexts.)