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A Class K fire extinguisher is designed specifically for kitchen fires caused by fats, oils, and grease. These fires often start near deep fryers or stovetops where cooking oils are heated to extreme temperatures.
Unlike general-purpose extinguishers, Class K models use a potassium-based wet chemical. When discharged onto burning oil, the chemical reacts through a process called saponification. This turns the hot grease into a thick, soapy foam that cools the surface and blocks oxygen, stopping the fire and preventing it from reigniting.
They’re also rated for Class A fires (solid combustibles like paper or wood), but their real value is in managing the unique dangers of kitchen-based oil fires.
Class K extinguishers are designed specifically for kitchen fires, but they’re just one part of a broader fire protection strategy. Other extinguisher classes handle different types of fires:
- Class A: For ordinary combustibles like wood, cloth, and paper.
- Class B: For flammable liquids such as gasoline, oil, and paint.
- Class C: For electrical fires involving wiring, appliances, or outlets.
- Class D: For combustible metals, typically used in labs and manufacturing settings.
For a complete overview of how each extinguisher type works, see this guide to fire extinguisher types.
When Do You Need a Class K Fire Extinguisher?
If your kitchen works with oil and high heat, the answer is yes. Here are common setups where a Class K extinguisher is essential:
You run a professional kitchen
- Restaurants with fryers or flat tops
- Hotels or resorts with buffet or banquet service
- Cafeterias in hospitals, schools, or correctional facilities
- Ghost kitchens and commercial food prep spaces
You cook in a mobile food business
- Food trucks or trailers
- Outdoor catering setups with portable fryers
- Festival or event kitchens
You manage bulk or off-site food production
- Commissary or central kitchens
- Remote catering facilities
- Live cooking stations at events
You deep fry or cook with oil at home
- Turkey fryers, woks, or large-volume oil setups
- Outdoor kitchens and built-in grills
- High-heat recipes using animal fats or vegetable oils
Install extinguishers within 30 feet of cooking equipment and train your staff or family members on their use. Practicing safe habits and preventing kitchen fires before they start is just as important.
Why Class K Fire Extinguishers Are The Only Option for Grease Fires
Grease fires spread faster than you can react
In commercial and home kitchens, oil can reach its ignition point in seconds. Once it does, grease fires can leap from a pan to nearby surfaces and spread rapidly.
Water can cause a fireball
Pouring water on burning oil creates a violent steam explosion, throwing flaming grease in all directions. It’s one of the most dangerous reactions in fire emergencies.
ABC extinguishers don’t neutralize grease fires
Using a dry chemical ABC extinguisher in a grease fire can blast hot oil across surfaces. It doesn’t cool the oil or prevent flare-ups. It also leaves behind corrosive residue that can ruin equipment and contaminate prep areas.
Class K extinguishers cool and smother effectively
These extinguishers release a fine, low-pressure mist that reacts with hot oil to form foam. That foam cools the fire source and seals it from oxygen, stopping the fire and preventing it from restarting.
They minimize damage and downtime
Class K models leave behind a light foam that’s easy to clean. Their gentle discharge avoids splashing grease-key in tight kitchens where safety and speed matter. After use, be sure to follow safe steps for cleaning up fire extinguisher residue.
Commercial kitchens are legally required to have them
Class K extinguishers are not optional in commercial kitchens. UL 300 standards mandate Class K extinguishers in any kitchen using high-temperature cooking oils. Skipping them risks fines, shutdowns, and more severe fire damage.
What to Look For in a Class K Fire Extinguisher
Not all extinguishers are the same. Here’s what matters:
- UL listing for Class K (non-negotiable)
- Potassium-based wet chemical agent
- Long spray time (look for ~50-60 seconds)
- Fine mist nozzle to avoid oil splash
- Simple pull-and-spray operation
- Minimal cleanup required
Size your extinguisher to match your cooking setup. Larger fryers or high-output kitchens should use higher-capacity models.
How to Maintain & Inspect a Class K Fire Extinguisher
If you’re budgeting for protection, here’s what to expect for fire extinguisher inspection costs.
Fire protection only works if it’s ready to go. That means checking, servicing, and recharging your Class K unit on schedule.
Inspection frequency matters. Here’s how to stay fire-ready:
Every month:
- Confirm the pressure gauge is in the green
- Inspect for rust, dents, or tampering
- Make sure the pin and tamper seal are secure
Once a year:
- Schedule a certified fire technician to inspect it
- Log the service date on the tag
- Check all hardware and nozzle components
When needed:
- Recharge after any discharge
- Replace expired or damaged units
Professional servicing includes internal checks, resealing, and testing. Don’t skip it. This is your front-line defense.
Stay Ready, Stay Safe
Class K fire extinguishers aren’t optional. They’re essential for any kitchen that deals with hot oil. Fires from grease or fat move fast and can overwhelm even a trained team without the right equipment.
If you manage a restaurant, run a food truck, or cook high-heat meals at home, now’s the time to make sure your fire protection is up to code and up to the task.
Contact B&W Fire Security for help choosing the right unit and setting up regular maintenance.
FAQ
Do I need a Class K fire extinguisher at home?
If you deep fry, use woks, or cook with oil regularly, yes. Fires involving hot grease can escalate quickly and aren’t manageable with water or a standard ABC extinguisher.
Can I use an ABC extinguisher on a grease fire?
No. It can actually spread the flames or worsen the fire. ABC extinguishers are not safe for oil-based fires.
What is saponification?
It’s a chemical reaction between the potassium in a Class K extinguisher and hot oil. It creates a soapy foam that cools the oil and seals it off from oxygen, stopping the fire.
Are Class K fire extinguishers expensive?
They typically cost more than ABC models, but the added safety and legal compliance for commercial kitchens make them well worth it.
How many Class K fire extinguishers do I need?
Follow fire codes and manufacturer guidelines. In general, place one Class K unit within 30 feet of each major cooking appliance.
Do Class K fire extinguishers require maintenance?
Yes. Monthly checks and annual servicing are essential to stay compliant and prepared.
Can I use a Class K fire extinguisher on gasoline or alcohol fires?
No. Use a Class B extinguisher for flammable liquids not related to cooking.
