Commercial kitchens are high-energy, high-temperature environments where things move fast and sometimes get dangerously hot. Among the most serious hazards in these settings are Class K fires, which involve cooking oils and fats used in deep fryers, griddles, and other high-heat appliances.
These aren’t your average kitchen fires. Class K fires burn at extremely high temperatures and behave differently than other types of fires, requiring a specialized approach to both prevention and suppression. Whether you manage a restaurant, cafeteria, or any facility with a commercial kitchen, you need to understand Class K fires so you can keep your people and property safe.
What Is a Class K Fire?
A Class K fire is a type of fire that results from combustible cooking media, such as vegetable oils, animal fats, or grease. These materials burn at extremely high temperatures, well over 600°F, which is why Class K fires can be especially difficult to extinguish.
Why Are Class K Fires So Dangerous?
- High Heat: Cooking oils can reach ignition temperatures faster than expected, especially if left unattended.
- Reignition Risk: Even if a fire is put out temporarily, residual heat can cause it to flare back up.
- Water Makes It Worse: Pouring water on a grease fire causes the burning oil to splatter and spread, making the fire much more dangerous almost instantly.
Because of their intensity, Class K fires demand specific safety measures and response tactics, not just general-purpose extinguishers.
“NFPA statistics show that for eating and drinking establishments, the majority of fires occur in the kitchen and specifically involve cooking equipment. Fire extinguishers that are rated for Class K fires (those involving animal fats or cooking oils) are the only type of extinguisher that can be used on fires involving animal fats or cooking oils. This is because many other types of extinguishers will either be ineffective or could even make this type of fire worse.” (What Is a Class K Fire Extinguisher?)
How to Prevent Class K Fires
The best way to deal with a Class K fire is to prevent it from happening in the first place. Here are a few best practices for keeping your commercial kitchen fire-safe:
- Keep Equipment Clean: Grease and oil buildup on appliances, hoods, and vents acts like fuel for a fire. Make sure stoves, fryers, filters, and exhaust systems are cleaned regularly and thoroughly.
- Monitor Oil Temperatures: Always use fryers with working thermostats and keep a close eye on oil temperatures. Overheated oil can ignite quickly and without warning.
- Don’t Leave Cooking Unattended: Even a minute away from an active stove or fryer can be too long. Fires can ignite and spread in seconds.
- Train Your Staff: Make sure your team knows how to use Class K fire extinguishers and understands what not to do in the event of a grease fire (like reaching for water).
What to Do If a Class K Fire Starts
Even with solid prevention measures, accidents can still happen. Here’s what to do if a Class K fire sparks in your kitchen:
1. Do Not Use Water
This is the golden rule. Water causes oil fires to splatter and spread, often making things worse in an instant. Never attempt to douse a grease fire with water.
2. Use a Class K Fire Extinguisher
These extinguishers contain a wet chemical agent that cools the hot oil and creates a barrier to prevent reignition. They’re specifically designed for kitchen grease fires and are the only safe option for this type of emergency.
3. Activate the Kitchen Fire Suppression System
Modern systems, like Amerex kitchen fire suppression systems, automatically detect fires and discharge suppression agents over cooking surfaces. They also shut off fuel sources (gas or electric) to prevent the fire from growing.
If your system is manual or partially automated, make sure staff are trained on how to activate it quickly and safely.
4. Turn Off Heat Sources
If it’s safe to do so, shut off burners, fryers, or other appliances to prevent the fire from reigniting. Some suppression systems will do this automatically.
5. Evacuate and Call Emergency Services
If the fire isn’t contained immediately, evacuate the building and call 911. Even after a fire appears extinguished, always have the area inspected before resuming operations.
Why Kitchen Grease Fires Need Class K Extinguishers
When a grease fire breaks out, not just any extinguisher will do. Using the wrong type, like a standard ABC or CO₂ extinguisher, can actually make a Class K fire worse. For example, spraying water on burning oil causes it to rapidly expand into steam, violently splattering the flames and spreading the fire.
Even CO₂ extinguishers, while effective on some fire types, won’t fully cool cooking oil. The top layer may go out, but the heat underneath can cause reignition. And the force of the expelled gas can spread the oil, turning a small fire into a much bigger problem.
That’s why you need Class K fire extinguishers in your commercial kitchens. These extinguishers release a wet chemical agent that reacts with the oil to create a foam-like barrier (a process called saponification) that cools, smothers, and seals off the fire.
According to NFPA 10, Class K extinguishers must be installed within 30 feet of cooking equipment where grease or oil fires could occur. They serve as backup to your hood suppression system and are a vital part of any kitchen’s fire safety plan.
Make sure your extinguishers are:
- Clearly labeled as Class K
- Mounted near cooking areas (but not too close to be inaccessible)
- Inspected regularly and always in working order
Staying Ready, Staying Safe
Class K fires are serious, but with the right knowledge, equipment, and training, they’re manageable. The key is prevention first, and preparedness always.
Make sure your kitchen is equipped with:
- A reliable kitchen fire suppression system
- Regularly inspected Class K fire extinguishers
- Trained staff who know how to respond
- A maintenance schedule for all fire safety equipment
Automatic kitchen suppression systems are designed to detect and suppress fires before they grow. But like any system, they need regular maintenance and inspection to stay reliable.
For more on choosing the right fire suppression system for your kitchen, check out our recent post: Choosing the Right Commercial Kitchen Fire System.
Midwest Fire & Safety works with commercial kitchens of all sizes to ensure they’re protected with the right systems, from suppression units to extinguishers, and that everything stays up to code.
Have questions about your kitchen fire safety setup? Contact them today to learn how they can help protect your kitchen, your team, and your business from Class K fire hazards.