What is a Class K Fire Extinguisher Used For?

Posted August 06, 2019 by Koorsen Fire & Security

What is a Class K Fire Extinguisher Used For?

Fires are classified by the type of fuel that feeds them. These classifications help determine what extinguishing agents will (or will not) be effective at putting them out, and therefore, which class of fire extinguisher to use. 

One of the trickier and more dangerous fires to combat are the Class K fires which are most common in commercial kitchens. These fires require a unique extinguishing agent to get them under control. 

Read on to learn more about what qualifies as a Class K fire and what types of extinguishers are rated specifically as Class K fire extinguishers. 

What are Class K Fires? 

Class K fires are those that are fueled by flammable liquids unique to cooking, such as cooking oils and greases that are vegetable and animal fat-based. 

When these substances reach high temperatures, as they naturally do in the kitchen, a sudden and potentially volatile fire can easily ignite. They can rapidly spread due to the flammability of the substance. 

Due to the high volume of cooking done in commercial kitchens (which include not only restaurants but cafeterias, food trucks, bakeries, and catering businesses as well), Class K fires are a common and constant threat. Therefore, for the safety of those in the kitchen as well as the patrons, it is vital that the correct fire extinguishers (as well as suppression systems) are in place. 

NOTE: It is important to discharge the hood suppression system prior to using the Class K fire extinguisher. If the suppression system has been installed and maintained correctly – when activated, all of the power and gas to anything under the hood should shut down. This shut down and the suppression system will make fighting the fire with a Class K extinguisher safer if necessary. 

What Types of Extinguishers are Rated as Class K Fire Extinguishers? 

While Class K fires do involve flammable liquids, please be aware that Class B fire extinguishers (rated for flammable liquids such as petroleum and gases) are not efficient to handle the high-temperature cooking oil and grease fires that occur in kitchens. 

It’s also important to remember that the use of water on cooking oil and grease fires will only spread the fire since the oil is not absorbed into the water but rather transported by it. Never use water on a fire involving grease or oil. 

Only Class K fire extinguishers are adequate for Class K fires and should always be close at hand in a commercial kitchen. These extinguishers use extinguishing agents that separate the fuel from the oxygen and help to absorb the heat elements of the fire triangle (fuel, heat, oxygen + chemical reaction). 

Currently, the only effective extinguisher rated as Class K is the Wet Chemical fire extinguisher. These extinguishers use a wet mist containing an alkaline mixture, like potassium carbonate, potassium acetate, or potassium citrate, which interact with the cooking media (oil, grease, or fat) to create a type of foam that blankets the oil or grease, cooling it and preventing it from being fed oxygen. The extinguishing agent successfully quenches the fire and also lessens the risk of reignition. 

Wet chemical extinguishers are a newer development. They have been created as the use of vegetable oils, which have a higher auto-ignition temperature than do animal fats, has increased, making the once effective dry chemical extinguishers ineffective. Newer types of efficiency fryers, which retain heat longer and are prone to reignition, have also contributed to the need for this more effective extinguishing agent. 

In addition to being able to extinguisher Class K fires, Class K fire extinguisher can also, in many cases, be effective at putting out a Class A fire that began in the kitchen as a result of the Class K fire. So, in essence, even if the flames spread to Class A fire materials within the kitchen, a Class K extinguisher should be able to handle it.

Once again, it is important to remember that other extinguishers, even if they are rated for Class B or multiple other classes of fires, will not be effective on the unique cooking media that fuel a class K fire. 

Remember to always use the kitchen hood fire suppression system first if a fire occurs. The Class K extinguisher can then be used to prevent reignition & protect against associated fires. 

Do You Have the Right Fire Extinguisher? 

Is your kitchen or workspace protected by the right fire extinguisher? Having the wrong extinguisher could result in increasing the risks and damages from a fire. 

Give the experts at Koorsen a call to discuss your unique setting and learn what extinguishers and protection will be best for you. Increase your safety and peace of mind by talking with a representative today. 

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Topics: Fire Extinguisher

Disclaimer: The information in this article is for informational purposes only. It is believed to be reliable, but Koorsen Fire & Security assumes no responsibility or liability for any errors or omissions in the content of this article. It does not constitute professional advice. The user of this article or the product(s) is responsible for verifying the information's accuracy from all available sources, including the product manufacturer. The authority having jurisdiction should be contacted for code interpretations.