In the extinguisher rating 2-A:10-B:C, what does the C rating indicate?

• A. It indicates the agent is cyanoacrylate base.
• B. It can be used on energized electrical equipment.
• C. The lack of a number following the C means it is not suitable for use on any electrical fire.
• D. The agent is carbon-tetrachloride base.

Answer: (B)

The C rating signals safety around electrical fires. When an extinguisher shows a C rating, it means the extinguishing agent is non-conductive and appropriate to use on energized electrical equipment. This doesn't rely on a numerical size for electrical fires; instead, the C designation tells you it’s suitable for electrical hazards, allowing you to apply it to live equipment when needed.

In the given rating, the other parts (A and B) indicate effectiveness on ordinary combustibles and flammable liquids, while the number after B relates to the amount of flammable-liquid fire it can handle. The choices mentioning a cyanoacrylate base or a carbon tetrachloride base aren’t what the C rating is about, and carbon tetrachloride extinguishers are obsolete due to toxicity. The important takeaway is that the C rating means it can be used on energized electrical equipment.