Wet Chemical Fire Extinguisher

Wet chemical fire extinguishers are a relatively new addition to the world of portable fire-suppressants, designed solely with the purpose of fighting deep fat cooking fires (which involve animal fat or vegetable oils). No other extinguisher can do the job they do. They are such an innovation that a separate class of fire, Class F, was created for the classification of deep fat cooking fires, and a new British Standard, BS 7937:2000 had to be written for them. The original model of this type was created by Chubb, although there are now many others available on the market.

This type of fire extinguisher usually comes in a 6 litre size, which means it is easy to handle, and the extinguishing agent is so effective it is able to tackle a 75 litre fat fire, even if the temperature of the burning fat is at 340 degrees. Different sizes of canister will suit different size capacity fryers, so the right size should always be purchased. The wet chemical has a saponification effect that creates a thick foam, which smothers the oxygen supply to the fire and prevents it from re-igniting. The chemical will cool the fat but not instantaneously, it needs to be left to do so for a short while.

Wet Chemical Fire ExtinguisherOften a slightly different shape to other extinguishers, and easily identifiable by the band of bright yellow somewhere in the upper half of the canister, the majority of wet chemical extinguishers have a long, thin hose and nozzle applicator as the exit route for the agent. This allows the operator to keep well away from the burning fire (in case of any splash back, which although very unlikely with this type of fire-suppressant, could cause great harm). The method used to apply a wet chemical fire extinguisher is different to that of other types, so individuals located in an area where this agent is present should be suitably trained in using it. It is fairly common to see wet chemical fire extinguishers located alongside CO2 ones, particularly in industrial kitchens or restaurants.

How to use a wet chemical fire extinguisher

When applying a wet chemical fire extinguisher onto a fire, the hose and nozzle should be held at arm’s length and applied in slow, circular movements. The resulting mist of chemical may appear too gentle a method to look like it would be effective; however this fine spray covers the greatest area possible to the burning fat, before the chemical turns it into a foamy substance, sealing and extinguishing it. Wet chemical should always be applied with great care, since smoke and fumes can result. Of course, wherever possible the source of the heat should be turned off before any attempt to tackle the fire is begun.

Although a wet chemical fire extinguisher should not be used on a fire involving live electricity, it does possess a safety feature in that the nozzle has passed the BSi 35kv conductivity tests, so if electrical items are accidently sprayed in a fire situation, the operator of the extinguisher will not be harmed. If necessary, a wet chemical extinguisher can also be applied to a Class A or Class B fire, if a more suitable extinguisher is not available at the time, which makes it a very versatile product.

Category: Fire Extinguisher Types