A Guide to Wet Chemical Fire Extinguishers
Wet chemical fire extinguishers
are the only ones suitable for cooking fires, and can be used on:
- Class A: Ordinary combustibles: wood, paper, cloth, rubber and plastics
- Class E: Electrical fires
- Class F: Cooking fats, lard, butter and oils
How to recognise them
Wet chemical fire extinguishers are easy to recognise with their bright yellow labels and red writing. It’s important that you purchase an accompanying identification sign.
As cooking and kitchen fire extinguishers
Wet chemical fire extinguishers are the only ones suitable for use on cooking fires. Other fire extinguishers are unsuitable because:
- They can cause splash backs
- They will often just spread the fire
Even Class B extinguishers that can be used on flammable fluids shouldn’t be used on cooking oils – their agents are released at a high pressure and can cause splash backs.
Wet chemical fire extinguishers are specially designed to react with cooking oils, without causing splash backs or spreading the fire.
How they work
Wet chemical fire extinguishers release a fine mist, which has two purposes when used on class F fires (cooking oils and fats).
1. Firstly, the mist cools the fire and lowers its temperature through evaporation. This stop the fire from spreading, and prevents the splashing of hot oils and fats.
2. Secondly, the mist released contains a chemical additive that reacts with the burning oils or fat to produce a non-combustible soapy layer. The process is called saponification.
The soapy layer acts as a barrier between the oxygen and the burning oil. Without oxygen, the fire will no longer be able to burn.
On class A fires
Wet chemical fire extinguishers can also be used to fight class A fires, but may not be as strong as other extinguishers, such as water fire extinguishers.
Wet chemical fire extinguishers release their contents at a significantly low pressure. This will reduce your risk of being splashed with hot oil.
Additionally, the extinguishers have a long applicator lance, allowing you to fight a fire from a safer distance.
By turning the source of fuel into a soapy substance, and by lowering the fuel’s temperature, the chance of re-ignition is very low.
Wet chemical fire extinguishers have several fire ratings, which are numbers followed by a letter. The letter tells you what type of fire it can fight, while the number next to it tells you how large this fire can be.
The most important rating you should look for is one that includes the letter ‘F’. This tells you that the extinguisher is suitable for cooking fires. The number next to it, will tell you the capacity of oil it is suitable for use on.
For instance, ‘25F’ will be found on a wet chemical extinguisher suitable for up to 25 litres of oil.
For more information on fire extinguisher ratings click here
Kitchens are normally quite steamy. For this reason, it’s best to choose a wet chemical fire extinguisher with a non-corrosive cylinder that’s suited to this environment.