Use a Class C-rated extinguisher if you cannot cut the power to the source. The acceptable type of fire extinguisher in this situation depends entirely upon if you are able to cut the power to the source or not. If you don’t know where the breaker is, the box is locked, or it would simply take way too long to access, then you must use a Class C-rated fire extinguisher.[6] Class C extinguishers are either carbon dioxide (CO2) or dry chemical extinguishers, and they will specifically include “Class C” on the label on the canister.[7]
o To use the extinguisher, pull any pin stopping you from depressing the handle, point the horn at the base of the fire, and hold down the handle.[8] As you see the flames shrinking, approach the source and continue spraying until the fire is fully extinguished.[9]
o If you cannot extinguish the fire within five seconds of using the extinguisher, then it’s too large.[10] Evacuate to a safe place and call 911.
o Since the faulty wiring is still receiving power in this case, the fire can reignite. You should still cut power to the source as soon as possible.
o You must use a Class C extinguisher because they contain non-conductive substances. A Class A extinguisher will only contain highly pressurized water, which conducts electricity and can create electrocution risks.[11]
o Another way to identify CO2 and dry chemical extinguishers is by their red coloring (water extinguishers are silver). CO2 extinguishers also have a hard horn at the tip instead of just a hose, an they lack a pressure gauge.[12]