Somebody searching for a "class C fire extinguisher" is usually standing in front of a panel, a rack, or a UPS, working out what to hang beside it. What comes back is a wall of units in several agents, all carrying the same letter, with nothing explaining why.
The confusion is built into the rating. A, B, and D describe fuels; K describes cooking media. C describes none of those — and unlike A and B, it never carries a number. It is not a size.
What the C on the label means
Amerex's Classes of Fire table defines Class C in three words: "Live electrical equipment." What the C certifies shows up in how Amerex describes each agent that carries one. ABC dry chemical "will not conduct electricity back to the operator." Purple K "is electrically nonconductive." Carbon dioxide "is electrically non-conductive." Halotron BrX lists "No electrical conductivity back to the operator." Even water mist qualifies — its misting nozzle "provides safety from electrical shock," and Amerex's owner's manual notes those units "are UL Listed for Class A and Class C fires."
The counter-example is the 2.5 gallon Model 240 water extinguisher, which has no C. The same manual: "Never use involving flammable liquids or gases or live electrical equipment," and its nameplate carries "the international red slash across the Class B and Class C symbol."
The C means the agent and its discharge stream will not carry current back to your hand. That is the whole claim — nothing about capacity, and nothing about what the agent does to the equipment afterward.
The C never carries a number
Read down Amerex's rating column: the A and the B are numbered, the C is not.
| Agent | Model | Capacity | Amerex published UL & ULC rating |
|---|---|---|---|
| ABC dry chemical | B456 | 10 lb | 4A:80B:C |
| Purple K | B460 | 10 lb | 80B:C |
| Carbon dioxide | 322 | 5 lb | 5B:C |
| Carbon dioxide | 330 / 331 / 332 | 10 / 15 / 20 lb | 10B:C |
| Halotron BrX | 347TS / 547, 349TS / 549 | 3.75 lb | 5B:C |
| Halotron BrX | 351 / 551 | 12.5 lb | 2A:10B:C |
| Halotron I | 398 | 15.5 lb | 2A:10B:C |
| Water mist (deionized) | C270 / C272 | 1.75 / 2.5 gal | 2A:C |
| Water | 240 | 2.5 gal | 2A — no C; red slash over the B and C symbols |
Two rows do most of the work. The 15 lb and 20 lb CO2 units carry the same 10B:C as the 10 lb — doubling the agent changes the rating not at all. And the water mist units are rated 2A:C: that is water, carrying a Class C. If C measured electrical firefighting power, a deionized water extinguisher wouldn't have one. (For how A and B numbers are assigned, see what fire extinguisher UL ratings actually mean.)
Why "Class C rated" doesn't settle a server room
ABC dry chemical and Purple K carry a C at every portable size Amerex builds. Neither is what Amerex recommends near electronics, and the owner's manual says so:
"Dry chemical is not recommended for fires in delicate electrical equipment or aircraft. Use of this agent may extinguish the fire but may damage the equipment beyond repair."
The C qualifies the agent for operator safety on energized equipment; it does not qualify the agent for the equipment. A dry chemical unit in a rack room means mono ammonium phosphate or potassium bicarbonate over every board; Amerex describes the ABC agent as melting "at approximately 350°F" and coating "surface where it is applied" (see Purple K vs ABC dry chemical).
Amerex's own Hazard Analysis chart routes around it. Under "Clean Agent" the listed applications open with Computer Server Rooms and Telecommunications; the catalog's applications page answers Data Centers with "Clean Agent, HT Series." Carbon dioxide is listed against Welding Shops, Auto Repair Shops, Manufacturing Facilities and High-Voltage Electrical Distribution.
That last entry is why CO2 is a fixture around energized electrical gear, and Amerex reinforces it elsewhere: CO2 also appears in the catalog's healthcare, education and light-to-medium industrial application lists. The disagreement is narrower than "CO2 or clean agent." High-voltage electrical distribution is the room Amerex's chart gives carbon dioxide; the server floor is not. Both agents leave no residue, both are C-rated, and Amerex still points them at different rooms.
Amerex is direct about why, in its own words on the HT Series: "THE HIGH PERFORMING HT-SERIES for commercial settings, once exclusive to the aerospace industry, can safely put out fires without damaging electronic equipment, specialized machinery, or other delicate materials. That also means that there is no clean-up or down time for your operations."
First, the two model numbers on one extinguisher
Amerex publishes this agent under two model families and the catalog prints both, which reads as two ranges when it is nearly one. The Halotron BrX page lists A337TS, 339TS, 347TS, 349TS and 351; the HT Series page lists A537TS, 547, 549 and 551. The published specifications match line for line — 5B:C, 3.75 lb, 9 seconds, 10–12 ft, 896 ft³ and 100 PSIG for the 347TS and the 547 alike; 2A:10B:C, 12.5 lb, 16 seconds and 2,988 ft³ for the 351 and the 551.
What separates them is the part number and what ships in the box. The BrX page is the aviation line: Amerex prints "Models 339, 347, 349 and 351 are FAA approved in accordance with DOT/FAA/AR-01/37" and gives the included bracket as Aircraft — the 898TS on the 3.75 lb units. The HT Series page carries no FAA row and is written "for commercial settings" as a "PREMIUM PRODUCT FOR HIGHLY TECHNICAL ENVIRONMENTS," shipping a wall bracket: the 853 Wall on the 547 and 549, with the 898TS available as an option. The 12.5 lb 351 and 551 both ship a wall bracket. So choosing between 347TS and 547 is a choice of paperwork and mounting hardware, not of agent, charge or rating.
CO2 versus Halotron BrX, side by side
Every figure below is from Amerex's published catalog tables.
| Specification | 322 CO2 | 330 CO2 | 332 CO2 | 547 / 347TS | 549 / 349TS | 551 / 351 |
|---|---|---|---|---|---|---|
| UL & ULC rating | 5B:C | 10B:C | 10B:C | 5B:C | 5B:C | 2A:10B:C |
| Capacity (lbs.) | 5 | 10 | 20 | 3.75 | 3.75 | 12.5 |
| Shipping weight (lbs.) | 13.1 | 28.25 | 50.75 | 4.79 | 5.04 | 19.88 |
| Discharge time (sec.) | 9 | 11 | 19.2 | 9 | 9 | 16 |
| Initial range (ft.) | 3–8 | 3–8 | 3–8 | 10–12 | 10–12 | 15–17 |
| Temperature range | −22°F to 120°F | −40°F to 120°F | ||||
| Valve | Chrome-plated brass | Anodized aluminum | ||||
| Minimum confined space (ft³) | Not published — see warning below | 896 | 896 | 2,988 | ||
| Manufacturer's warranty | 5-year | 6-year | ||||
Reach. The range row is the sharpest split in the table, and the CO2 manual turns it into an instruction: move "to within approximately 8 feet [2m] (2 1/2 & 5 lb) or 10 feet [3m] (10, 15 or 20 lb) of the fire site." In a hot aisle with equipment on both sides, that approach distance is a constraint.
Weight. A 20 lb CO2 unit ships at 50.75 lbs; the 12.5 lb 551 ships at 19.88 lbs and adds a 2A the 332 does not carry. (Those are the HT Series page's shipping weights; the BrX page publishes filled weight — 5.50 lbs for the 347TS, 5.75 for the 349TS.) Amerex builds the CO2 line on "rust-free aluminum cylinders" with chrome-plated brass valves; the BrX units use anodized aluminum valves and, per the catalog, "aluminum cylinders (Model 551 uses a steel cylinder)."
The A rating. No Amerex CO2 portable carries one. Amerex's Classes of Fire table lists Class A as "Wood, paper, rubber, fabrics, and many plastics" — which covers a good deal of an equipment room. The 351 and 551 are rated 2A:10B:C. What CO2 has in return: Amerex calls it "a clean, non-contaminating, odorless gas" that "Meets many hospital medical equipment requirements," and it is rechargeable — Amerex publishes a recharging procedure for it.
The confined space number nobody reads
Halotron BrX extinguishers carry a minimum confined space figure on the nameplate, and Amerex's owner's manual is explicit: "Neither Halotron I, Halotron BrX nor Halon 1211 should be used in confined areas smaller than indicated on the extinguisher nameplate, food preparation areas or in the presence of people with cardiac problems."
Those figures scale with agent charge — 427 ft³ for the 1.79 lb A537TS, 896 ft³ for the 3.75 lb 547 and 549, 2,988 ft³ for the 12.5 lb 551. In a small comms closet the 551's figure can exceed the room's volume while the 547's does not — the dimensions decide the model.
CO2 has no published minimum but the same problem in a different form: Amerex's CO2 manual warns that prolonged occupancy of "a small room, closet or other confined area" after discharge "can result in loss of consciousness due to oxygen deficiency."
When the room has a magnet in it
Where a room excludes magnetic hardware, the model number carries what the rating doesn't. Amerex builds a nonmagnetic 5 lb CO2, the 322NM, which the catalog states is "independently tested and approved for use in MRI facilities to 11.7 Tesla." Amerex's own fitment chart ships the 322NM on an 801SS wall bracket rather than the standard 801 listed for the 322; the 2026 item list describes that part as "BKT WALL 801 5.0 CO2 SS STAINLESS STEEL." The Parts Book numbers the same two hangers 00546-P and 17737 rather than 801 and 801SS; that mapping runs through our CO2 weight checks, hydro and parts platforms guide. The same item list carries a nonmagnetic 15 lb CO2 — "FE 331 15. CO2 NON MAG," item 6902, rated 10B:C — alongside a nonmagnetic 7 in. round bracket, "BKT ASY 810 RD 7" NM NONMAG." A nonmagnetic cylinder on a magnetic hanger defeats the exercise; our bracket fitment guide maps the assignments by cylinder diameter.
Service life, and the 12-year clock
This is the difference buyers find out late. Amerex's catalog states, in capitals across the BrX page: "HALOTRON BrX EXTINGUISHERS HAVE A 12-YEAR SERVICE LIFE AND ARE NON-RECHARGEABLE." The owner's manual repeats it — BrX units "shall be removed from service 12 years from date of manufacture on the UL nameplate" — and its six-year maintenance requirement adds "Excludes Halotron BrX extinguishers." A BrX unit is a sealed twelve-year asset — inspected, then replaced.
Carbon dioxide runs the opposite way: it is rechargeable, it has no gauge to read — Amerex has those units weighed or hefted instead — and Amerex puts it on a five-year hydrotest rather than the twelve years its dry chemical units get. Both the weight check and the interval are set out in Amerex CO2 is different; the replace-or-recharge arithmetic is in recharge or replace.
The practical rule
Racks, patch panels, control rooms, clean rooms, telecom closets: a clean agent — Amerex names computer server rooms and data centers for it, and the 351 and 551 add the 2A CO2 lacks. High-voltage electrical distribution, welding shops, auto repair shops: CO2 is what Amerex lists against those spaces. Neither, if the space is smaller than the nameplate allows. On placement and quantities, Amerex's direction is that "The most current issue of NFPA-10 should be consulted for minimum recommended fire extinguisher types, placement, and travel distances" — a conversation for your authority having jurisdiction.
What we stock
Carbon dioxide portables — the 322 5 lb at 5B:C, and the 330 10 lb, 331 15 lb and 332 20 lb, all three at 10B:C. Nonmagnetic: the 322NM and the 15 lb 331 non-magnetic.
Halotron BrX, the FAA-approved build — the 347TS nozzle unit and the 349TS with hose at 3.75 lb, and the 351 at 12.5 lb and 2A:10B:C.
HT Series, the same agent and charge on a wall bracket — the 547, the hose-equipped 549, and the 551.
Full ranges live in the CO2, Halotron BrX and wheeled CO2 collections; everything for equipment rooms is gathered under server rooms and electronics.
Specifying for a data hall, a lab or a plant floor? Send us the room dimensions and what's in them, and we'll come back with options and lead time — request a quote.
Sources
Class definitions, agent descriptions, ratings, published specifications, confined space figures, bracket assignments, hydrotest intervals and application listings come from Amerex Corporation's Hand-Portable Fire Extinguishers catalog (HP Volume 26, Issue 1), the Owner's Manual Hand Portable (No. 27794), the Owner's Service Manual for Carbon Dioxide Portable Extinguishers (Manual P/N 05603), and Amerex's 2026 published item list. Confirm any critical rating, space requirement or bracket assignment against the extinguisher's own label and Amerex's current documentation, and confirm hazard classification, placement and quantities with a qualified fire protection professional and your authority having jurisdiction.
ShopAmerex.com is owned and operated by Centurion Holdings Group LLC, an independent authorized distributor of Amerex Corporation products. We sell equipment and factory OEM service parts — we do not perform inspection, service, hydrostatic testing or recharging.