If an extinguisher bears a red square with a letter, it is rated for which class?

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

Answer: (B)

Understanding fire extinguisher classifications helps you pick the right tool for a fire. A red square with a letter on an extinguisher marks the class it’s rated to fight. A red square with the letter B means it’s for Class B fires—flammable liquids such as gasoline, oil, and solvents. These fires involve liquids that burn and require extinguishing methods that cool or separate the fuel from the air, which is what this type of extinguisher is designed to do. Other classes cover different hazards: Class A for ordinary combustibles like wood and paper, Class C for energized electrical equipment, and Class D for combustible metals. If an extinguisher can handle several classes, you’d see multiple letters indicating its broader effectiveness.