Class F Fires Explained

Fires are separated into different classes depending on the type of fuel that’s burning. Each class of fire requires a different type of extinguisher, and using the wrong extinguisher on the wrong fire can increase the risk to the person using it.

Class F fires are most commonly associated with cooking oils and fats, which means they require specialist fire safety equipment. In commercial kitchens, restaurants, takeaways, hotels, catering environments, and other food preparation areas, Class F extinguishers are used to help control these risks safely.

In this blog, we’ll explore Class F fires in more detail, including what causes them, how Class F fire extinguishers work and when they’re needed, and how to reduce the risk of kitchen fires.

What are Class F fires?

Class F fires are caused by the ignition of cooking oils and fats. These fires occur when oils or fats reach extremely high temperatures and ignite. Cooking oils can reach their flash point at around 135°C, while autoignition can occur at around 340°C. This means the oil or fat can catch fire without a visible flame or other ignition source.

Class F fires are particularly dangerous because hot oil and fat can burn intensely, spread quickly, and reignite if not cooled properly. They’re most often linked to cooking equipment such as:

• Deep fat fryers
• Chip pans
• Frying pans
• Griddles and commercial cooking equipment
• Oil filled cooking appliances
• Fat or grease build up around cooking areas

Class F fires are common risks in both domestic and commercial kitchens, but they’re especially important in food led businesses where large volumes of oil or fat may be used everyday.

It’s also important to understand that Class F fires aren’t the same as Class B fires. Class B fires involve flammable liquids such as petrol, paint, or solvents, while Class F fires specifically involve cooking oils and fats. Because of this, they need a specialist extinguisher designed for that risk.

What are Class F fire extinguishers and how do they work?

Class F fire extinguishers are designed to control fires involving cooking oils and fats. The most common type is a wet chemical fire extinguisher, which is used to cool the burning oil and help stop oxygen reaching the fire.

When a wet chemical extinguisher is used, the agent is applied gently over the flames. A layer forms on top of the burning oil, helping to smother the fire and reduce the chance of reignition. These extinguishers also use potassium salts, which help reduce the flames and support the cooling process.

When using a wet chemical extinguisher, you should stand at a safe distance from the fire and apply the spray carefully. The extinguisher should be positioned so the chemical falls gently onto the fire from above, rather than being blasted directly into the oil. This helps avoid splashing and allows the agent to work effectively.

Only trained staff should attempt to use a fire extinguisher. If the fire is too large, if oil is splashing, or if there is no clear escape route, the safest option is to evacuate immediately.

Where are Class F extinguishers needed?

Class F extinguishers are needed in environments where cooking oils and fats create a fire risk. This is particularly important in commercial kitchens and food preparation spaces where fryers, pans, and cooking equipment may be used for long periods.

Class F fire extinguishers may be required in:

• Restaurants
• Cafés and coffee shops
• Takeaways and fast food premises
• Hotels and hospitality venues
• Commercial kitchens
• Catering facilities
• Schools and colleges with a kitchen
• Care homes with kitchen facilities
• Staff canteens
• Food production areas
• Any premises using deep fat fryers or large quantities of cooking oil

The exact extinguisher requirements will depend on a few factors including the layout of your premises, the cooking equipment used, the size of the kitchen, and the findings of your fire risk assessment. A small staff kitchen may not need the same level of provision as a busy commercial kitchen with multiple fryers.

Can I use fire blankets on Class F fires?

In addition to wet chemical extinguishers, fire blankets are often present in commercial kitchens. Made from fire resistant materials, a fire blanket works by smothering a small fire and cutting off its oxygen supply.

Fire blankets can be useful for small contained pan fires, but they shouldn’t be treated as a replacement for suitable Class F fire extinguishers in commercial kitchen environments. Both pieces of equipment can play an important role, depending on the size and nature of the fire.

Like fire extinguishers, fire blankets should be stored in an easily accessible location. Staff should also understand when and how to use them safely.

To use a fire blanket, remove it from its casing and hold it by the straps attached. If safe to do so, turn off the gas and electricity supply before attempting to extinguish the fire. Wrap the top of the blanket around your hands to help protect them from the heat, roll up any long sleeves, and place the blanket carefully over the fire.

A fire blanket should only be used on a fire that is smaller than the blanket itself. Once in place, leave the blanket covering the fire for at least 60 minutes to reduce the risk of reignition.

What should you avoid using on a Class F fire?

Using the wrong equipment on a Class F fire can be extremely dangerous. Cooking oil and fat fires behave differently from many other fire types, and applying the wrong extinguishing method can cause the fire to spread or reignite.

You should avoid using:

• Water, as it can cause burning oils to splash and spread the fire
• Standard CO2 extinguishers, as they may not cool the oil enough to prevent reignition
• Standard foam extinguishers, unless they’re specifically suitable for the fire risk
• Dry powder extinguishers, unless they’re specifically rated and appropriate
• Any extinguisher you haven’t been trained to use
• Any method that involves moving a burning pan or fryer

You should never try to carry a burning pan or move burning cooking equipment. This can cause serious burns, spread the fire, and put other people at risk.

If you’re unsure which extinguisher to use, or whether it’s safe to tackle the fire, evacuate the building and call the fire and rescue service.

How to avoid Class F fires

Class F fires are particularly common in kitchens because oils and fats are regularly heated to high temperatures. The best way to reduce the risk is to control cooking processes carefully, keep equipment clean, and make sure staff understand the dangers.

Some other ways you can prevent Class F fires include:

• Never leaving hot oil or fat unattended
• Not allowing cooking oil to overheat
• Turning off the heat if oil begins to smoke
• Cleaning up oil and fat spillages quickly
• Removing grease build up from surfaces, extraction systems, and surrounding areas
• Keeping towels, packaging, paper, and other flammable materials away from hobs and fryers
• Making sure open flames and hobs are turned off when they’re no longer needed
• Training staff on kitchen fire risks and emergency procedures
• Keeping suitable Class F extinguishers and fire blankets easy to access
• Arrange regular fire extinguisher servicing and replacement where needed

If you’re cooking with oil and fat and notice smoke coming from the pan, turn the hob off or remove the pan from the heat if it’s safe to do so. Be sure to allow the oil to cool before continuing. Smoke is a warning sign that the oil is getting too hot and could become dangerous.

Need a Class F fire extinguisher for your kitchen?

Whether you’re cooking in a restaurant or a small café, it’s important to stay vigilant to the potential causes of fire. A small mistake involving hot oil or fat can quickly become a serious incident if the right precautions aren’t in place.

At City Fire Protection, we supply, install, and maintain high quality fire extinguishers for commercial kitchens and businesses across London, Birmingham, and the wider UK through the LS Fire Group. We can help you choose the right fire extinguisher type for your premises, as well as provide fire safety training for your staff so they have a full understanding on how to use them.

If you’re looking for Class F extinguishers for your kitchen, further fire safety equipment for your premises, or you’d like further advice on Class F fires, get in touch with our team today who are on hand to help.