All fire extinguishers work by removing one or more of the 3 key elements that are required for a fire to flourish.
Wet chemical fire extinguishers are filled with potassium, which cools and lowers the temperature of the fire, therefore stopping the fire from spreading.
When the fire extinguisher is used, the potassium sprays out in a fine mist which then reacts with the fats and oils in the fire (class F fire). This creates a soapy layer on the surface which smothers, cools and extinguishes the fire.
It is advised that Wet chemical fire extinguishers, foam extinguishers and water extinguishers should never be used on fires that involve electrical appliances and equipment (class E fire.)