Definition
A fire involving energized electrical equipment, such as wiring, motors, generators, transformers, or avionics, where the electrical current is still present. Extinguishing requires a non-conductive agent (such as carbon dioxide or a clean agent like Halon or its modern replacements) so the person fighting the fire is not exposed to electric shock and the agent does not conduct current back to the source.
Plain English
A fire in equipment that still has electricity flowing through it. You cannot use water or any agent that conducts electricity, because the current is still live.
Context Anchor
Seen in aircraft maintenance, cockpit emergency procedures, and fire extinguisher selection around batteries, wiring, motors, generators, and avionics.
Derivation
The U.S. National Fire Protection Association (NFPA) sorts fires into letter classes (A, B, C, D, K) based on what is burning. Class C specifically marks fires where live electricity is the defining hazard — not the burning material itself, but the current behind it.
Why Pilots Care
Using the wrong extinguisher on a Class C fire can electrocute the person fighting it and spread the fire further. Knowing the class tells you immediately which extinguisher to grab and whether to cut power first.
Intuition Check
Do not confuse a Class C fire with Class C airspace. In fire protection, “Class C” does not mean a location or level of seriousness; it means the fire involves electrical equipment that may still be powered.
Example Sentence 1
When smoke appeared from the avionics rack, the technician grabbed the CO2 extinguisher because a Class C fire was suspected.
Example Sentence 2
Never use water on a Class C fire in the cockpit because the liquid can conduct electricity to the crew.