What Is a Class K Fire Extinguisher? Guide for Canadian Restaurants

Cooking oil and grease fires are among the most dangerous fires in any commercial kitchen. They burn extremely hot, spread fast, and react violently to the wrong extinguisher. That's why NFPA 10, the standard on portable fire extinguishers, calls for a Class K fire extinguisher wherever there is a risk of fires involving cooking oils and animal fats, especially around deep fat fryers. In Ontario, the Fire Code requires Class K extinguishers to protect commercial cooking operations.

Why ABC, CO2, and Water Extinguishers Fail on Grease Fires

An extinguisher that isn't rated for Class K fires can make a cooking oil fire worse. Water flashes to steam and splashes burning oil. A CO2 extinguisher may knock down flames on the surface, but the oil underneath holds its heat, so the fire can reignite once the CO2 runs out. The force of the discharge can also push burning oil outside the fryer.

How a Class K Extinguisher Works

Class K extinguishers are usually wet chemical units. The agent reacts with hot cooking oil to form a soapy foam layer on the surface, a process called saponification. That layer seals off oxygen and cools the oil to stop re-ignition. Class K units also discharge at a gentler rate than Class B extinguishers, so the agent settles on top of the oil instead of splashing it.

Where to Install Class K Extinguishers

• Within 9 m (30 ft) of any cooking appliance that uses oil or grease, per NFPA 10, which Canadian fire codes reference. Check your provincial fire code and local fire department for exact placement
• Near deep fat fryers, woks, griddles, and other high-risk cooking stations
• As a backup to the kitchen hood suppression system, which should be activated first in a commercial kitchen fire
• Alongside ABC extinguishers for ordinary combustibles and electrical hazards elsewhere in the kitchen

Class K vs. Class B: What's the Difference?

Class B extinguishers are designed for flammable liquids like gasoline and solvents. Class K extinguishers are designed for deep cooking oil and fat fires in cooking appliances. Class K ratings have no number in front of the letter: an extinguisher earns the rating by passing a single pass-or-fail test under UL 711 / CAN/ULC-S508, putting out a vegetable oil fire in a deep fat fryer without re-ignition or splashing. In Canada, choose a ULC-listed Class K extinguisher.

PASS Method: Pull the pin, Aim low, Squeeze the handle, Sweep side to side. Activate the hood suppression system first, and train every kitchen employee before an emergency.