Throughout my years consulting on kitchen safety, I’ve witnessed how fires separated into distinct classes can confuse people when choosing the right extinguisher. The type of fuel that’s burning determines everything. Using the wrong fire suppression method doesn’t just fail, it can increase risk to the user dramatically.
Like City Fire Protection emphasizes, understanding Class F fires, their causes, and how to extinguish and avoid them is crucial. I’ve seen buildings with kitchens where staff couldn’t distinguish between fire types. Modern fire classification systems exist because different materials burn in different ways, requiring specific extinguishing agents. When properly classified, responding to a fire emergency becomes intuitive. Understanding these classifications can genuinely save lives and reduce damage in critical moments.
What are Class F fires?
Class F fires involve the ignition of cooking oils and fats, making them particularly dangerous. These flammable liquids reach their flash point around 315°c, and at 340°c or 340°C, they achieve autoignition, meaning they burst into flames without any flame or ignition source. I’ve responded to incidents where fat and cooking oil created what’s technically a sub-class fire, yet they burn at significantly higher temperatures than conventional fires.
Unlike petrol with its low auto ignition and flash temperatures, fats require intense heat. This unusual flash point earned them their own category. The nature of these liquids means they predominantly occur in kitchens, often from negligence in food preparation facilities, pans left unattended, oil/fat spillages on surfaces, or unchanged oil in deep fat fryers. Whether it’s rapeseed, palm, vegetable, sunflower, or olive oil, they all ignite quickly, spread rapidly, and prove difficult to extinguish. However, risk can be minimised through regular cleaning, oil-changing procedures, and effective extraction equipment.
How do you extinguish a Class F fire?
To properly extinguish a Class F fire, you need a wet chemical fire extinguisher—all others are unsuitable and dangerous. The process works when sprayed, forming a layer over burning oil, cutting off oxygen and preventing worsening fire. The potassium salts work at reducing the flame. Position yourself at a safe distance above the flames, squeeze the lever, and let chemical spray fall onto the fire to suffocate it, which helps eliminate reignition risk. Understanding three elements—fuel, oxygen, and heat—is essential.
With burning liquid, you’d reduce heat below the flash point, but extreme temperature of fat and oils makes this hard to achieve. Most extinguishers prove inadequate; using a water fire extinguisher causes a massive explosion, helping fire grow by spreading oil with water. CO2 fire extinguishers and powder extinguishers create more problems than solutions, increasing danger to the building. They must be treated with equipment tailored for fat that can smother oxygen feeding the fire.
If possible, turn off the heat source. For a small fire, a fire blanket can put it out in early stages by depriving oxygen, preventing it from growing. When too large, the wet chemical fire extinguisher is the only option. Use slow, controlled, sweeping motion, forming a soapy layer that will cool and smother the fire.
How to avoid Class F fires
- Preventing incidents in domestic kitchens and commercial kitchens requires minimising risk by never leaving pans with hot oil or fat unattended and cleaning up spillages quickly.
- Take care not to use too much oil, never fill a pan more than one-third full. Don’t leave pots and pans unattended or get distracted while cooking.
- For deep fat frying, the safest way uses a thermostatically controlled electric fryer preventing oil from reaching dangerous temperatures. When you see smoke, immediately turn off heat.
- Consider installing a heat detector or fire alarm installation to provide early warning if things overheat. Place an optical smoke alarm outside the kitchen to detect smoke from cooking-related fires.
- Ensure open flames and hobs are turned off when no longer needed, keep flammable materials a safe distance from the hob, and training staff is critical for reducing risks.
Fire blankets
Beyond wet chemical extinguishers, fire blankets should be present in all commercial kitchens as accessible first response. Made from fire-resistant material, the blanket works by smothering and extinguishing flames through cutting off the oxygen supply. Like fire extinguishers, they’re stored in an easily-accessible location. To use a blanket, remove it from its casing and hold by straps attached.
Ensure gas/electricity supply is turned off before attempting to extinguish the fire. Wrap the top round your hands to prevent burns, and roll up any long sleeves to ensure they don’t set alight. Carefully place the blanket over the fire, an important note: they’re only used on fires smaller than the blanket itself. Leave the blanket in place for at least 60 minutes after the fire is extinguished.
What are the Common Causes of Class F Fires?
The most common cause of Class F fires stems from deep fat frying, particularly in kitchens where oil or fat is cooking at extremely high temperatures. They typically occur during igniting moments when temperature control fails. These incidents represent the source of roughly 20% of all accidental fires in the home that the fire service attends to every year. According to a Home Office study examining fires across
England between April 2023 and March 2024, cooking appliances emerged as the largest ignition category for accidental dwelling fires, accounting for 44% of all incidents. Given this high risk and frequency, it’s absolutely advisable to know exactly how to prevent and successfully put out these dangerous events before they escalate.
How Class F Fire Extinguishers Work
Fat fires run very hot, so hot that standard fire extinguishers become not just unsuitable but actively dangerous to use on a fat fire. They must only be extinguished using a wet chemical fire extinguisher containing potassium salts that simultaneously cool the flames and form what’s called a saponification blanket.
This effectively smothers the flames with a thick, soapy foam barrier. Like all fire extinguishers, your Class F fat fire extinguisher should be clearly marked with British Standards Institute certification, specifically the BSI standard BS EN3, plus a BS (BSI) Kitemark indicating BAFE (British Approval for Fire Equipment) approval and a CE stamp. They’re in bright red colour with a bright yellow label positioned above the instructions panel for easy identification. For fat fryers that hold more than three litres of oil, you must have one on premises as a legal requirement under the Regulatory Reform (Fire Safety) Order 2005. Larger commercial installations may require a fixed fire system like an Ansul or Amerex fire system.
Why Insurance Companies May Require Class F Fire Extinguishers in Kitchens
Many insurance companies insist that a wet chemical fire extinguisher be positioned within easy reach of any deep fat frying equipment and regularly maintained under contract. Proper fire extinguisher servicing and replacement protocols ensure these important extinguishers remain fully operational and ready for use when emergencies strike.
If you have any doubts about the function or condition of any fire extinguisher, it’s often cheaper and easier to replace it entirely than to service it. In a busy kitchen environment, extinguishers get exposed to significant environmental wear and tear compared to other locations. A straight replacement proves quick and easy, without the worry of unexpected costs for spare parts. From an underwriting perspective, insurers recognize that properly maintained equipment drastically reduces claim frequency and severity.
Conclusion
To wrap up, understanding Class F fires and how to control them is vital for maintaining kitchen safety. These fires, often sparked by overheated cooking oils or fats, demand the correct response using wet chemical extinguishers and fire blankets to prevent rapid spreading. Regular staff training, equipment maintenance, and adherence to safety protocols can make all the difference in preventing serious damage or injury. Keep your workplace secure and compliant by investing in reliable fire protection tools.
Visit K Force Security to get certified fire safety equipment and expert solutions tailored for your kitchen.