Wet Chemical Fire Extinguisher
Information and Advice

How To purchase Fire Extinguishers (UK Only)

If you are interested in purchasing fire extinguishers or any other type of fire safety equipment, I can recommend Screwfix, who offer a wide range of equipment at very competitive prices, with next day delivery.

They have over thirty years experience and are one of the largest and most reliable suppliers in the UK. You can view their workplace safety equipment page here.

See Also The Following Pages:

Main Fire Extinguishers Page

Water Fire Extinguishers

Carbon Dioxide Fire Extinguishers

Dry Powder Fire Extinguishers

Halon Fire Extinguishers

Fire Extinguisher Ratings

How To Use A Fire Extinguisher

The History Of The Fire Extinguisher

Wet Chemical Fire Extinguisher:
Class K Fire Extinguisher Or Class F Fire Extinguisher?

To avoid any confusion, let me first explain that fires involving burning oils are known as Class K fires in the US, and as Class F fires in the UK, Europe and Australasia. For full details of fire classifications see the Fire Extinguisher Ratings page.

The wet chemical fire extinguisher was developed specifically to deal with deep fat cooking fires. They are a relatively recent development and the new Class F fire classification had to be devised for them in the UK, along with a new British Standard BS 7937: 2000.

The wet chemical fire extinguisher is the only type of fire extinguisher that should be used on burning cooking oil. Other types cannot deal with the extremely high temperatures at which oil burns, and the failure to effectively cool the oil can cause flashbacks.

Wet Chemical Fire Extinguisher - The Chemical Reaction

Other types of fire extinguisher will not cool burning oil and may cause it to splash around, either spreading the fire or injuring the fire fighter. The other standard fire fighting measure for use on burning cooking oil is the fire blanket. Do not attempt to use anything other than a fire blanket or wet chemical extinguisher on a burning deep fat fryer.

The wet chemical fire extinguisher works by using a process called saponification, whereby a chemical additive reacts with the oil to form a thick soapy substance. This soapy layer puts a non-combustible seal between the oil and the oxygen it needs to burn, and so extinguishes the fire and prevents re-ignition. The saponification process is endothermic, meaning that it absorbs heat, so the process of creating the soapy layer also takes heat out of the oil and cools it down. The cooling process is not a particularly dramatic effect so should be given time to allow it to happen.

Wet chemical fire extinguishers are also safe to use on Class A fires, which are normal combustible materials such as paper, wood, etc. They are not designed for use on electrical fires, but most will be safe if accidentally sprayed on nearby electrical equipment. Check the fire extinguisher rating to be sure.

The specific use and purpose of wet chemical fire extinguishers means that the usual place to deploy them is in a commercial kitchen environment where grease and deep fat fryers are common. This makes them particularly suited to restaurants, takeaways, burger vans, cafes, work canteens, etc.

Wet Chemical Fire Extinguishers - How They Work

All fires require three things in order to happen - an ignition source, oxygen and fuel. All fire extinguishers work by removing at least one of these things, making it impossible for the fire to continue burning. In the case of the wet chemical fire extinguisher, the main factor is cutting off the fuel (oil) from the oxygen supply (the air) by putting a non-combustible layer of soapy chemical between them. It also has a cooling effect on the fuel, which helps to prevent re-ignition.

Like most fire extinguishers, wet chemical fire extinguishers are available in two main types, stored pressure or cartridge operated. The commonest is the stored pressure type, where the pressurised gas is in the main chamber with the chemical. The cartridge operated type have a separate gas cartridge inside the main extinguisher cylinder, making it easier to recharge the extinguisher after use.

Wet Chemical Fire Extinguisher - Other Considerations

As the only time you are going to rely on fire fighting equipment could be a life and death situation, it is best not to take chances with the quality of fire extinguisher that you purchase. There are certain approvals to look for, which (if genuine!) tell you that the fire extinguisher has been made to certain standards and tested against set criteria.

The European Standard for portable fire extinguishers is BS EN 3, so look for this as one indicator that the manufacturer and product have passed certain tests. The letters 'CE' on the product also mean that the fire extinguisher has met all the European directives relating to it.

Also in the UK there is the British Standards Kitemark, which confirms that the product has reached set criteria set out by the British Standard. It is not a legal requirement for a product to have this mark.

Other Considerations

• a five year guarantee is a reasonable expectation on a quality appliance
• if the extinguisher is going to be situated in a steamy kitchen environment, ensure that is is made from non-corrosive material.
• Look for a wall bracket or floor stand to be included for fixing.
• Wet chemical fire extinguishers normally come in 3 litre and 6 litre sizes, though you will find some slightly smaller and slightly larger.

Wet Chemical Fire Extinguisher - Use and Training

No-one should attempt to fight a fire with a fire extinguisher unless they have received the proper training in how to use the equipment. Basic operating instructions are printed on every fire extinguisher, and you should ensure you fit an identification sign immediately above the extinguisher to aid easy identification in an emergency.

Every wet chemical fire extinguisher should come with a long applicator or lance, making it easy to apply the chemical to the burning oil. This should be done in slow circular motions.

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