Fire Extinguishers
Class C Fire Extinguishers
The C is the only letter on an extinguisher label that is not a quantity. Knowing what it certifies changes what you should be shopping for.
By Ryder M.Last reviewed
A Class C fire extinguisher is certified for use on energized electrical equipment — the C means the extinguishing agent is non-conductive, so discharging it will not carry current back up the stream to you. It is a yes-or-no property, not a quantity, which is why there is never a number in front of the C. In US homes that means an ABC dry-chemical unit: essentially every one sold in the consumer channel carries the C. What you must never use is water or foam. And if you can kill the power first, the fire stops being Class C at all.
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What Class C actually means
Class C is the classification for fires involving energized electrical equipment — a live panel, an outlet, a motor, an appliance still plugged in, a charger, a light fitting.
The important thing to understand is that electricity is not a fuel. Nothing burns because it is electrical. What burns is insulation, a stud, a circuit board, carpet, a cardboard box — ordinary Class A material, or sometimes a Class B liquid, that an electrical fault has ignited.
So Class C does not describe the fire. It describes a condition the fire is happening under: the equipment is still live, so anything you spray at it is a potential path to earth through your hands.
That is why the C certification is about the agent rather than the fire. Under UL 711 testing, the C designation certifies that the extinguishing agent is non-conductive — that discharging it at energized equipment will not conduct current back up the stream to the operator.
And it is why the C has no number and never will. The A number relates to the size of ordinary-combustible fire the unit extinguished in test; the B number to the square footage of flammable-liquid fire. Both are quantities. Non-conductivity is a property of an agent: it is either true or it is not, and there is no scale to put on it. The full classes reference sets out all five letters.
For the remaining letter, Class D fire extinguishers covers combustible metals — magnesium, titanium, sodium and the rest — and explains why a home almost never has that hazard at all.
What carries a C, and what must never touch live equipment
Agent by agent. The left column is what is in the extinguisher, not what the fire is made of.
| Agent | Carries a C? | Why | Found in |
|---|---|---|---|
| Monoammonium phosphate (ABC dry chemical) | Yes | Non-conductive powder; the standard US residential agent | Essentially every home ABC extinguisher |
| Sodium / potassium bicarbonate (BC dry chemical) | Yes | Non-conductive; no A rating, so it does not cover ordinary combustibles | Some commercial and vehicle units |
| Carbon dioxide (CO2) | Yes | Non-conductive gas that leaves no residue — the reason it is used around equipment worth saving | Commercial, server rooms, labs. Rare in homes |
| Clean agents (halocarbon, inert gas) | Yes | Non-conductive and residue-free; designed to protect the equipment as well as the room | Data centers, aviation, studios. Not a consumer product |
| Water | No — never | Water conducts. Discharging it at live equipment can put current through the operator | Class A only units, offices, hotel corridors |
| Foam (AFFF and similar) | No — never | Water-based, so it conducts for the same reason | Class A/B units, fuel handling |
| Wet chemical (Class K) | No | Water-based potassium solution for cooking oils; not rated for live equipment | Commercial kitchens |
| Aerosol extinguishing sprays | No published rating | Sold as extinguishing aerosols, not as rated A:B:C portable extinguishers | Kitchen drawers, vehicle glove boxes |
Ratings are produced under UL 711 testing. An extinguisher either carries the C on its label or it does not — do not infer it from the agent name on a retail listing.
Quick picks
Scored against carries the c, agent quantity, build and serviceability, meets a 2-a minimum and aftermath on electronics. Tap a row for the full write-up. The price in each buy button is the live Amazon price at the last check, stamped with the date it was taken.
| # | Product | Best for | Score | Price |
|---|---|---|---|---|
| 1 |  Amerex B500 5 lb ABC Dry Chemical Extinguisher 2-A:10-B:C, 5 lb, all-metal. Carries the C and enough agent to use it. | The standard C-rated unit for a house | 7.9/ 10 | $75.01 · View on Amazon #ad how we are funded · price as of October 20, 2026 |
| 2 |  First Alert PRO10 Rechargeable Heavy Duty Extinguisher 4-A:60-B:C. The C plus the highest B rating here. | A workshop or a sub-panel | 8.0/ 10 | $72.98 · View on Amazon #ad how we are funded · price as of October 20, 2026 |
| 3 |  Kidde Pro 210 4 lb Multi-Purpose Extinguisher 4 lb at 2-A:10-B:C with the bracket in the box. | A C-rated unit that fits beside a panel | 7.3/ 10 | $54.97 · View on Amazon #ad how we are funded · price as of October 20, 2026 |
C-rated units worth owning
1. The standard C-rated unit for a house
Amerex B500 5 lb ABC Dry Chemical Extinguisher
2-A:10-B:C, 5 lb, all-metal. Carries the C and enough agent to use it.
- Listed to
- UL rated 2-A:10-B:C
- Sensing / agent
- Monoammonium phosphate dry chemical
- Power / service life
- Rechargeable; all-metal valve and body
If a page about Class C has one practical recommendation it is this unit, and the reason is that the C is not what makes it a good buy — every ABC unit in the consumer channel has the C. What separates them is agent quantity, build and whether you can mount it where it needs to go.
Five pounds matters here more than in most categories. An electrical fire rarely presents as an open flame you can see all of: it is behind a panel cover, inside a dishwasher, in a wall cavity, under a dash. You get at it through a gap, which means several short bursts rather than one sweep.
The all-metal construction is a durability argument rather than a performance one, and it is why this unit recurs across this site. The home roundup makes the full case.
What it does well
- Rated C — non-conductive monoammonium phosphate, certified for energized equipment
- 2-A:10-B as well, so it covers the ordinary materials an electrical fault sets alight
- All-metal valve and body, built to be recharged rather than discarded
- 5 lb of agent, which matters because electrical fires are usually inside a housing and take more than one pass
The downside
- Dry chemical residue is mildly acidic and hygroscopic — it frequently destroys the electronics it lands on
- 5 lb takes real grip to hold out and steer accurately
- Nothing about a C rating makes a fire inside a sealed wall safe to approach
Do not buy this if: the thing on fire is a computer, a rack or an instrument you hope to recover. Dry chemical will put the fire out and write off the hardware, and no consumer extinguisher is a clean-agent unit.
- All-metal valve rather than plastic, which is the difference between a serviceable unit and a disposable one
- Rechargeable, so a partial discharge during a small fire does not write off the extinguisher
- 2-A:10-B:C covers ordinary combustibles, flammable liquids and energized electrical equipment
- 5 lb is heavier than the supermarket unit and needs a proper bracket
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2. A workshop or a sub-panel
First Alert PRO10 Rechargeable Heavy Duty Extinguisher
4-A:60-B:C. The C plus the highest B rating here.
- Listed to
- UL rated 4-A:60-B:C
- Sensing / agent
- Monoammonium phosphate dry chemical
- Power / service life
- Rechargeable by a certified professional; all-metal construction with a commercial-grade metal valve and head; 12-year limited warranty
The rooms with the most electrical risk in a house are usually the rooms with the most of everything else: a workshop has a sub-panel, extension leads, chargers, a compressor and solvents within twenty square feet.
The C covers the ignition source; the B covers what it finds. A fault that starts in a charger and reaches a shelf of thinners is a Class B fire with an electrical cause, and 40-B is what the extinguisher needs for the second half of that sentence.
The garage roundup covers where to mount it and why beside the exit beats beside the bench.
What it does well
- 4-A:60-B:C — the C, plus six times the flammable-liquid rating of a standard home unit
- The right unit where electrical risk sits next to stored liquids: a garage, a workshop, a shed with a sub-panel
- Rechargeable with a metal valve
- More run time than any other unit here, which a fire inside a machine housing demands
The downside
- Heavy and bulky — a real control problem for anyone who cannot steer it one-handed
- Same dry-chemical aftermath, over a larger area
- Oversized for a hallway or an apartment kitchen
Do not buy this if: it is the only extinguisher in a small home. Put capability where the hazard is and keep something lighter where the people are.
- 4-A:60-B:C is a far larger rating than most home units — six times the flammable-liquid rating of the 10-B:C supermarket unit
- Rechargeable rather than disposable, with an all-metal valve and head
- Suits a garage, workshop or home office where liquids and equipment are the realistic risk
- Mounting bracket and a color-coded corrosion-resistant pressure gauge in the box
- Bigger and heavier, which is a real problem for anyone who cannot handle the weight one-handed
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3. A C-rated unit that fits beside a panel
Kidde Pro 210 4 lb Multi-Purpose Extinguisher
4 lb at 2-A:10-B:C with the bracket in the box.
- Listed to
- UL rated 2-A:10-B:C
- Sensing / agent
- Monoammonium phosphate dry chemical
- Power / service life
- Rechargeable; mounting bracket included
The practical argument for this one is mounting. A C-rated extinguisher wants to live near the panel and near the room's exit, and those are frequently cramped positions where a 5 lb body will not fit.
You keep the full class coverage — 2-A:10-B:C is the same label as the 5 lb unit — and what you give up is seconds of discharge rather than capability.
Where to mount a fire extinguisher covers the NFPA 10 heights and the positions that make a unit useless, of which beside-the-hazard is the commonest.
What it does well
- Reaches 2-A:10-B:C at 4 lb — the lightest body that still carries a 2-A rating
- Mounting bracket included, which is what gets an extinguisher onto a wall rather than a shelf
- Fits the narrow strip of wall beside a utility cupboard or a breaker panel
- Rechargeable
The downside
- Least agent of the rated units here, so little margin if the first burst misses
- 10-B is undersized for a workshop that stores fuel
- Same dry-chemical residue
Do not buy this if: the room is a workshop with flammable liquids. There the B number is the point of the purchase, and this is the wrong end of the range.
- 4 lb — the lightest unit that still reaches a 2-A rating, which matters for one-handed use
- Rechargeable, with the bracket in the box
- Same 2-A:10-B:C class coverage as heavier units, with less run time
- Less agent means less margin for error if the first attempt misses
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Kill the power and the fire stops being Class C
This is the most useful practical point on the page, and it is almost never said plainly.
A Class C fire is only Class C while the equipment is energized. Switch the breaker off, or pull the plug if the plug is not the thing burning, and what remains is an ordinary Class A or Class B fire. The conductivity constraint disappears and your options widen.
It also removes the fault that is still feeding the fire. A live circuit with a short in it keeps re-igniting its own fire no matter how much agent you put on the flames.
The caveat matters as much as the advice: do not go looking for the panel. If the breaker box is past the fire, in the same cupboard, or anywhere that is not already on your way, skip it entirely and use a C-rated extinguisher from a distance. The C rating exists precisely so that de-energizing is not a prerequisite.
And if the fire is inside a wall, a ceiling void or a sealed appliance housing, you cannot reach the seat of it at all. Get out, close the door, and let the fire service open the structure.
The mistakes that make a Class C fire worse
Each of these is common, and the first one is the dangerous one.
- Water on live equipment. The reason the C certification exists. Water conducts, and a stream from a bucket, a hose or a Class A extinguisher to live equipment can put current through whoever is holding it.
- Assuming a small unit has the C. It almost certainly does, but read the label rather than the listing description. An aerosol extinguishing spray is not a rated extinguisher and carries no A:B:C figure at all.
- Opening the appliance to look. A microwave, a dryer or a dishwasher with smoke coming out of it should be unplugged and left shut. Opening the door feeds it oxygen.
- Powering equipment back up after a discharge. Dry chemical residue is hygroscopic, so it absorbs moisture and becomes conductive on a circuit board. Have it cleaned or write it off, but do not energize it to see whether it still works.
- Leaving the residue in place. The damage that follows an electrical extinguisher discharge is mostly caused by the clean-up not happening the same day. The powder cleanup guide has the sequence and the protective equipment worth wearing.
- Treating a C rating as an electrical-fire capability score. It is not a score. It says the agent is safe to use, and nothing about how well the unit fights the fire — that is the A and B numbers plus agent quantity.
The clean-agent question, answered honestly
Readers who arrive on this page with a home office, a studio or a rack of hardware usually want the same thing: an extinguisher that puts the fire out without destroying the equipment.
That product exists and it is not sold in the consumer channel. Carbon dioxide and clean-agent extinguishers are non-conductive and residue-free, which is exactly why data centers and aviation use them, and they are priced and distributed for facilities rather than households.
Dry chemical is the trade a home makes. Monoammonium phosphate is mildly acidic and hygroscopic: it absorbs atmospheric moisture, and damp residue on a board is both corrosive and conductive. Hardware that survived the fire frequently fails weeks later from the agent.
For a house that is the correct trade every time — the structure matters more than the appliance. For a room full of hardware, the honest hedge is a bicarbonate aerosol in a drawer for the small, visible, already-unplugged fire, with the rated ABC unit by the door for anything larger. The aerosol comparison sets out both sides, including why an aerosol cannot be the only tool.
Where the C-rated unit should live
On the main level, on the route past the breaker panel, with the exit behind you. Never with the panel between you and the door.
One in the garage or workshop, larger and with a higher B rating, because that is where chargers, extension leads and flammable liquids share a bench.
Nothing mounted above an appliance or inside the cupboard that holds the hazard. The fixing point has to be reachable when the hazard is already alight, which rules out the position most people choose first.
Where to mount a fire extinguisher has the NFPA 10 heights — handle no more than 5 ft from the floor for units up to 40 lb, at least 4 in clear of it.
The detection point this page does not solve
Electrical fires have a long, quiet, smoldering phase. That is their defining characteristic and the reason so many start overnight inside a wall or a loft: a loose connection warms, insulation degrades, and the fire produces smoke for a long time before it produces flame.
Photoelectric smoke sensing responds fastest to exactly that profile, which is why every current alarm recommendation on this site is photoelectric. Ionization versus photoelectric is worth five minutes.
An extinguisher is the last line. The alarm that wakes you during the smoldering phase is worth more than any upgrade in rating, and interconnected alarms — one sounds, they all sound — are worth more still when the fault is two floors below the bedroom. The interconnected roundup covers the units.
Questions people actually ask
What is a Class C fire extinguisher used for?
What is in a Class C fire extinguisher?
Why is there no number before the C?
Can you use an ABC extinguisher on an electrical fire?
Should I turn the power off before using an extinguisher?
What should you never use on a Class C fire?
Do I need a separate Class C extinguisher for my house?
How these picks were chosen. On published specifications, safety listings and manufacturer documentation — plus the findings of organizations that do run tests. We have no laboratory and we do not burn anything. Read the full methodology.
Sources
- UL Solutions — Fire extinguisher testing and certification (UL 711)
- NFPA — NFPA 10, Standard for Portable Fire Extinguishers
- US Fire Administration — Home fire prevention
- CDC / NIOSH — Occupational exposure guidance and chemical databases
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