Class F Fire Explained

Fires are separated into different classes depending on the type of fuel that is burning. Each class of fire requires a different type of extinguisher – using the wrong extinguisher for the wrong fire can actually increase the risk to the user. In this article, City Fire Protection are going to look at Class F fires – we’re here to tell you what causes them, how to extinguish them, and how to avoid them.

What are Class F fires?

Class F fires that are caused by the ignition of cooking oils and fats. These fires occur when said oils or fats reach their flash point – in this case, flash point is around 315 °c. At 340°c, cooking oils and fats can achieve autoignition – that is to say they can set alight without a flame or other ignition source. These fires can be extremely dangerous and can spread very quickly.

How do you extinguish a Class F fire?

To extinguish a Class F fire, you need a wet chemical fire extinguisher. All other types of fire extinguisher are unsuitable for these types of fires. The process works like this: when the fire is sprayed, a layer is formed on top of the burning oil, which prevents oxygen from reaching and worsening the fire. These extinguishers also make use of potassium salts, which are effective at reducing the flame. 

When using a wet chemical extinguisher, ensure you’re a safe distance from the fire itself and position the extinguisher above the flames. Squeeze the lever to release the chemical spray, allowing it to fall onto the fire from above – this will suffocate it and the potassium salts will work to reduce the flame, eliminating the risk of reignition.

How to avoid Class F fires

These types of fires are particularly common in domestic and commercial kitchens, for obvious reasons. To minimise the risk of a Class F fire breaking out, it’s vital that any pans of hot oil or fat are not left unattended. Any spillages of these oils and fats must be cleaned up as quickly as possible, too.

If you’re cooking with oil or fat and you start to see smoke coming from the pan, either turn the hob off or remove the pan from the heat altogether and let the oil cool before continuing. 

When cooking with oils and fats, make sure open flames and hobs are turned off when they are no longer needed. While these may not result in a Class F fire, they can easily turn into fires of other classifications – a flame from a hob can ignite a hand towel or some kitchen roll, and the fire can spread exponentially from there. For this reason, it’s important to make sure that flammable materials are kept a safe distance away from the hob where possible.

Fire blankets

In addition to your wet chemical extinguishers, fire blankets are usually present in commercial kitchens. Made of fire-resistant material, the blanket smothers the fire and extinguishes it by cutting off its oxygen supply. Like fire extinguishers, the blankets should be stored in an easily-accessible location.

To use the blanket, it needs to be removed from its casing and held by the straps attached. The gas/electricity supply must be turned off before attempting to extinguish the fire. Wrap the top of the blanket round your hands to prevent burns, and roll up any long sleeves to ensure they don’t set alight, and then place the blanket over the fire. It’s important to note that fire blankets should only be used on fires that are smaller than the blanket itself. Leave the blanket in place for at least 60 minutes after the fire has been extinguished. 

Whether cooking at home or working in a busy commercial kitchen, it’s important that we stay vigilant to any potential causes of fire. By having your wits about you at all times, you can avoid a small mistake turning into a potentially disastrous situation. 

City Fire Protection are proud to provide the highest quality fire extinguishers to customers around the country. As a leading independent fire safety company, we stock only the highest standard of equipment and deliver the highest standard of service. We can deliver and install all types of fire extinguishers to your property, as well as training staff to ensure your business is appropriately equipped to prevent the spread of fire. 

For more information about our fire extinguishers, our fire safety training or any of our state-of-the-art fire safety equipment, contact us today.