Purple K Fire Extinguishers
Purple K fire extinguishers are the standard choice wherever flammable liquids and gases are stored, pumped or burned. Purple K is a potassium bicarbonate dry chemical developed by the U.S. Naval Research Laboratory in 1959 to fight fuel fires, and it puts out flammable-liquid fires more than twice as effectively as ordinary sodium bicarbonate powder. That extra knockdown power is why you find purple K extinguishers on airport ramps, fuel docks, refineries, drilling sites, chemical plants and naval vessels.
Every purple K extinguisher carries a B:C rating. It is built for flammable liquids and gases (Class B) and is safe to use on energized electrical equipment (Class C). It is not rated for ordinary combustibles like wood, paper and cardboard, so pair it with an ABC extinguisher wherever those materials share the space.
We stock purple K fire extinguishers from Buckeye and Badger in every size an industrial site needs:
- 2.5 lb and 5 lb units with vehicle brackets for trucks, fuel trailers and service vehicles
- 10 lb, 13.2 lb and 20 lb hand units, including high-flow models for pressurized gas and running fuel fires
- 30 lb offshore and cartridge-operated units for harsh outdoor and heavy industrial locations
- 50 lb and 125 lb wheeled units for tank farms, hangars and loading racks
Compare sizes, valves and mounting options below, or read our purple K buying guide further down the page to find the right unit for your hazard.
What Is a Purple K Fire Extinguisher?
A purple K fire extinguisher discharges a dry chemical made mostly of potassium bicarbonate, about 78 to 82 percent by weight. The rest is flow and moisture-resistance additives, and the powder is dyed purple so it is easy to tell apart from other agents. The "K" comes from potassium's chemical symbol. Purple K stops a fire by interrupting the chemical chain reaction in the flame, which is why it knocks down burning fuel so quickly. It is roughly four to five times as effective on Class B fires as carbon dioxide.
Purple K vs. Class K Fire Extinguishers
The names are easy to mix up, but the two do different jobs. A purple K extinguisher is a dry chemical unit for fuel, solvent and gas fires. A Class K extinguisher is a wet chemical unit made for commercial kitchens, where it cools and seals burning cooking oil in deep fryers. Do not use purple K in place of a kitchen extinguisher. For restaurants and food service, shop our Class K & kitchen extinguishers.
Where to Use a Purple K Fire Extinguisher
Fuel handling and aviation
Airport ramps, fuel docks, fleet fueling islands and bulk plants use purple K because spilled and spraying fuel spreads fast. Purple K is compatible with most firefighting foams, so it is often paired with foam on airport crash trucks.
Oil, gas and chemical processing
Refineries, drilling pads, pipelines and chemical plants handle pressurized liquids and gases. These fires are three-dimensional, which is where a high-flow purple K extinguisher earns its place.
Purple K fire extinguishers for cars and trucks
For a car, pickup or service truck, a 2.5 lb or 5 lb purple K unit with a vehicle bracket is a strong choice for fuel and engine fires. If the vehicle also carries paper, upholstery or cargo, an ABC unit gives broader coverage.
How to Choose the Right Purple K Fire Extinguisher
Size and B:C rating
The number in front of the B is roughly the square footage of flammable-liquid fire the extinguisher can handle. Larger cylinders carry higher ratings and longer discharge times. Match the rating to the largest spill or pool fire you could realistically face.
Standard vs. high-flow purple K extinguishers
Fire codes call for high-flow extinguishers on pressurized gas and running or three-dimensional fuel fires. High-flow units discharge agent faster to overpower these fires before they re-flash.
Hand-portable vs. wheeled
For large tank farms, hangars and loading racks, a 50 lb or 125 lb wheeled purple K extinguisher delivers far more agent than any hand unit. See all our wheeled fire extinguishers.
Purple K Fire Extinguisher Care and Recharging
Never mix purple K with ABC (monoammonium phosphate) powder. The two react and the agent loses its effectiveness, so recharge only with purple K dry chemical recharge agent. Clean up discharged powder promptly, because it cakes into a crust when it mixes with water and fuel. Like other stored-pressure dry chemical units, purple K extinguishers need a monthly visual check, annual maintenance by a certified technician, a six-year internal examination and a 12-year hydrostatic test.