If an extinguisher bears a blue circle, it is rated for which class?

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

Answer: (C)

The marking system on extinguishers uses symbols or colors to show what kinds of fires the extinguisher is suitable for. A blue circle specifically indicates the electrical-fire rating—Class C. This matters because fires involving energized electrical equipment require non-conductive extinguishing agents, so you avoid water or other conductive substances. Dry chemical or CO2 extinguishers are typical for this class, making the blue circle the best clue that the extinguisher is for electrical fires. Other classes cover ordinary combustibles or flammable liquids, but the blue circle points to Class C.