| Type | How it works / Danger of use | | Wet chemical | Yellow |   | | Best for: | The specialist wet chemical extinguishers are ideal for Class F fires, involving cooking oils and fats, such as lard, olive oil, sunflower oil, maize oil and butter. | | | | Danger: | Check manufacturer's instructions for suitability of use. These extinguishers are not recommended for class B fires and home use. | | | | How to use: | Apply the wet chemical using the extended applicator in slow circular movements, which give a gentle, yet highly effective application. Apply the fine spray onto the burning fat until the surface of the burning cooking oil changes into a soapy like substance, this then prevents re-ignition. The gentle application helps prevent hot oil splashing onto the user. | | | | How it works: | Most class F extinguishers contain a solution of potassium acetate, sometimes with some potassium citrate or potassium bicarbonate. The extinguishers spray the agent out as a fine mist. The mist acts to cool the flame front, while the potassium salts saponify the surface of the burning cooking oil, producing a layer of foam over the surface. This solution thus provides a similar blanketing effect to a foam extinguisher, but with a greater cooling effect. The saponification only works on animal fats and vegetable oils, so class F extinguishers cannot be used for class B fires. The misting also helps to prevent splashing the blazing oil. Tests have established that a 6 litre extinguisher is capable of extinguishing a fire in a 75 litre capacity deep fat fryer. The extinguisher is easy to use producing a gentle but highly effective spray. | | |