Wet Chemical Fire Extinguisher

What Are Wet Chemical Fire Extinguishers?

Wet chemical fire extinguishers are specialised extinguishers designed to combat Class F fires caused by hot cooking oil and fats.

Class F fires burn at extremely high temperatures. They are caused by cooking fats and oils reaching their flash point (approximately 315°c). Class F fires are hazardous for two reasons:

• Class F fires burn at high temperatures preventing all extinguishing agents except wet chemical from suppressing the flames.

• Once the Class F fire reaches a temperature of around 340°c it will achieve autoignition. This means that even if fire suppression is initially achieved the flames may reignite themselves.

How Do Wet Chemical Extinguishers Work?

Wet chemical extinguishers work by cooling, smothering and preventing reignition.

• Step 1. Cool the Class F Fire: Begin by safely spraying the wet chemical agent onto the affected area. The fine mist will cool the burning fat or oil, lowering its temperature below the ignition point.

• Step 2. Smother the Class F Fire:  When the wet chemical is applied to burning oils or fat it triggers the process of saponification. This process creates a soapy, foam-like layer that seals off the oxygen supply and prevents reignition.

• Step 3. Prevent Reignition: After saponification, the wet chemical solution stays on the surface of the fire, preventing the flames from reigniting.

When Would You Use a Wet Chemical Extinguisher?

Wet chemical fire extinguishers are used to safely suppress Class F fires. If a hot oil fire starts in a restaurant kitchen, a Wet chemical extinguisher would be the ideal fire suppressant choice.