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Wet chemical fire extinguishers are one of the least common extinguisher types and are designed for use on Class F fires involving cooking oils.

Wet chemical extinguishers can also be known as Class F extinguishers or Class ABF extinguishers.

Wet chemical extinguishers can be used on:

  • Class A fires – combustible materials: caused by flammable solids, such as wood, paper, and textiles
  • Class F fires – cooking oils: such as olive oil or butter.

Some wet chemical extinguishers can be used on Class B fires (flammable liquid fires) so it is worth checking with your BusinessWatch engineer whether your wet chemical extinguishers are cleared for use on this type of fire.

Wet chemical fire extinguishers should never be used on the following fire types:

  • Class B fires – flammable liquids: such as petrol, paint or spirits UNLESS cleared for this type of use
  • Class C fires – flammable gases: like propane and butane
  • Electrical fires – electrical equipment: such as computers and photocopiers. Note though that once the electrical item is removed, the fire changes class

Identifying a Wet Chemical Fire Extinguisher

CO2 fire extinguishers have a yellow coloured label stating ‘WET CHEMICAL’. It should also have a sign above or next to the extinguisher that states ‘Wet Chemical Extinguisher’. A wet chemical extinguisher can also be differentiated due to its lance attachment and a longer than usual hose.

CO2 extinguishers come in foam sizes:

  • 2 litre
  • 3 litre
  • 6 litre

How Wet Chemical Fire Extinguishers Work

The chemical contained in a wet chemical fire extinguisher is potassium. When the trigger is pressed, potassium salts are expelled as a fine mist. This ensures that the burning fat or oil from aren’t spread to other materials. The potassium salts react with the oil to create a soapy like film on the fire surface. This creates a barrier between the fire source and oxygen, effectively smothering it, and also creates a cooling effect to help prevent re-ignition of the fire.

When to choose a CO2 Fire Extinguisher

Any commercial building with a professional kitchen or a deep fat fryer should be equipped with a wet chemical fire extinguisher. Such premises include chip shops, hotel kitchens and restaurants.

These kind of premises should also have the standard foam and CO2 extinguishers on site too to ensure that all fire risks are covered.

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