Deep fat fryer fires and pan fires with burning fat are difficult to extinguish. The jet of an ordinary extinguisher can carry the burning fat out of the pan and spread the fire, making the problem worse. Any traditional water based extinguishers can also be dangerous, as water droplets sink into the fat and then erupt violently, spreading the fire. The five most commonly used methods of extinguishing fat fires are:
Wet chemical extinguishers
Wet chemical fire extinguishers are usually supplied with a long lance which helps to safely deploy the foam. The wet chemical forms a thick soapy foam-like blanket over the surface of the burning oil/fat which stops oxygen from reaching the fire and smothers the flames. This process is known as saponification, which is an endothermic process that not only ensures that the additive penetrates the fat/oil and creates a seal, but also cools it to below the ignition temperature, thus preventing the oil/fat from re-igniting
Fire blankets are spread over the burning pot or pan and exclude oxygen which suffocates the fire. It is crucial to leave the fire blanket on top of the container even when the flames have gone, as the hot fat would re-ignite again should the blanket be removed.
Dry Water mist extinguishers
Portable dry water mist extinguishers create a microscopic mist with low pressure which settles onto the surface of the fire without sinking in. As the water droplets evaporate above the surface, the fire cools and oxygen is excluded. Dry water mist also protects the user from the flames, as the mist forms a heat barrier.
ABF fire extinguishers
These extinguishers resemble a normal fire extinguisher and contain a foam suitable for burning fat.
Whilst formally not classified as extinguishers, these foams are a low cost solution for domestic kitchens with cooking oil.