Wet chemical fire extinguisher employs a pressurized solution of alkali salts in water to extinguish fire. It is also known as Class F’ fire extinguishers or class ’ fire extinguishers in some versions.

Generally, wet chemical extinguishers are suitable for use on Class A & F Fires. The class A and F fires are fires involving cooking oils and fats (Class F fires), such as lard, olive oil, butter, vegetable oil, and on flammable solids (Class A), such as papers, woods, plastics, etc,

Why is wet chemical fire extinguisher best for class F fires

Due to high auto-ignition temperatures of cooking oil fires, they are difficult to extinguish. However, to extinguish these fires, it needs to be cooled sufficiently which conventional extinguishers are not as effective due to risk of flash back and re-ignition.

Moreover, the wet chemical extinguisher works best in this situation because it rapidly knocks the flames out, cools the burning oil and chemically reacts to form a soap-like solution, sealing the surface of the fire and preventing re-ignition.
Wet chemical fire extinguisher color

This type of fire extinguisher has a YELLOW colored label stating ‘Wet Chemical’.

According to the British standard, the main body of this extinguisher should be Red, and they should have a Large Yellow Banner across the top on the front of the extinguisher with Red writing stating “Wet Chemical”.


Wet Chemical extinguishers that are manufactured to BS EN 3 should have a red body (RAL 3000) and a yellow band covering 5-10% of the fire extinguishers surface area.

This extinguisher are available in sizes like;

How does wet chemical fire extinguisher work

It works by forming a soapy film on the surface of the fire. This is made possible by the wet chemical fire extinguishing agent (Potassium) present in the wet chemical fire extinguisher. This smothers the fire, with the added benefit that the mist also creates a cooling effect.

In summary, this extinguisher acts in two ways:

How to use a wet chemical fire extinguishers:

The wet chemical must be applied using the extended applicator or lance in slow circular movements, giving a gentle, yet thorough application in fine spray form, covering and emulsifying the burning cooking oil or fat to prevent re-ignition.

To operate the extinguisher, aim the applicator tip from a distance of about 1 meter from of the fire, squeeze the levers on the operating head together and attack the fire from the base in slow circular movements covering the complete area.

Breakdown of the steps to follow in extinguishing class F fire:

et chemical fire extinguishers are the new kids on the fire extinguisher scene, developed specifically for use on deep fat cooking fires. The first such extinguisher on the market was the Chub Fry Fighter, and its appearance gave rise to a new fire class, Class F and a new British Standard, BS 7937: 2000.

Wet chemical fire extinguishers are red with a yellow panel above the operating instructions.

How Wet Chemical Fire Extinguishers Work

Normal fire extinguishers are worse than useless in a deep fat fire, since they cannot cool the oil and cause hot oil to splash up on contact with the extinguisher’s agent. Fat can burn at 340 degrees, and an average fat fryer holds up to 75 liters of oil.

Unfortunately, until the invention of the wet chemical extinguisher, many commercial kitchens were supplied with foam or powder units with the occupants falsely thinking these could be used on the fat fryers. The cost can also be high compared to other extinguishers but the risks are much higher in the kitchen and, if bought online at a discounted, the costs are not high these days.

The active ingredient in a wet chemical fire extinguisher is potassium acetate, often with added potassium citrate or potassium bicarbonate. When operated, a wet chemical extinguisher creates a fine mist, which cools the flames and prevents splashing.

The potassium salts then have a sanctification effect on the oil’s surface, creating a thick, slippery foam layer that smothers the fat and prevents re-ignition. The chemical foam will also cool the fat over a prolonged period of time.

Unlike other extinguishers, the idea is to completely empty the contents into the fat fryer to enable the cooling process to begin.

A point to note is that the contents can be corrosive so the quality extinguishers are made from stainless steel. Beware of the cheap Middle-Eastern imports made from mild steel as the lifespan will not be as good and the linings could be affected.
Sanctification: Here’s the Science

Sanctification is the same process used to create soap from fats and oils as a result of a reaction with a metallic alkali, or base. The base acts on the oil to convert it into hydrolyzed acid and alcohol. Essentially, a wet chemical fire extinguisher converts the surface of the cooking oil or fat into a non-combustible soap.

An added benefit is that the soap-creation process is endothermic, meaning it absorbs heat energy from the oil, cooling the oil down in the process.
Using a Wet Chemical Fire Extinguisher

Like other specialist fire extinguishers, the wet chemical fire extinguisher has a long lance, allowing the user to stand well back from the fire and to spray the agent gently and evenly over the fire’s surface. As with all specialist extinguishers, full training should be given in the proper and effective use of this extinguisher, a common sight in commercial kitchens and food manufacturing environments.
Just Fats, Please

Wet chemical fire extinguishers only work with animal fats and vegetable oils, so they cannot be used on Class B fires involving flammable liquids such as petrol or diesel.

They have usually been tested to a 13A Class A rating but should not be specified for anything other than a kitchen.
Wet Chemical Fire Extinguishers and Electricity

Wet chemical fire extinguishers are not designed for use on electrical equipment, but in the modern kitchen environment, it is hard to avoid electricity cables. Hence, the lance of a standard wet chemical fire extinguisher is non-conductive, and passes the BS 35kv conductivity test.
Other Fire Extinguishers in the Commercial Kitchen

Wet chemical fire extinguishers have a very specific function, and are not suitable for other types except Class A fires if no other extinguisher is available.

Most Fire Risk Assessments would recommend that extinguishers are kept in proximity with other safety items such as a CO2 for electrical items, and a substantial blanket such as a 1.8m x 1.2m size. Fire blankets should be used to smother small pan fires, not to deal with commercial fryer fires.

A small fire blanket is a useful fire safety device for any kitchen, commercial or domestic. Simple to use, yet effective, it should be used to smother a fire and then LEFT ALONE for a considerable length of time to ensure the fire is completely extinguished. If in doubt, smother, get out, stay out and call the Fire Brigade.
Where Can Wet Chemical Fire Extinguishers Be Used?

A can be used in the following scenarios:

In addition, some of the chemical fire extinguishers that exist are allowed to be used in the case of a Class B fire (a fire that involves flammable liquids such as paint, diesel, and petrol). It is essential to check the label or to seek the advice of a fire safety professional in advance if you wish to have a fire extinguisher that can be used on such fire types.
Where Can Wet Chemical Fire Extinguishers Not Be Used?

Wet Chemical Extinguisher There are several instances when a should never be used, these are as follows:

How Do You Identify a ?

You can easily identify a by looking out for the following:

What Are Wet Chemical Fire Extinguishers Also Known As?

A can be known as one of two other names These are as follows:

How Do Wet Chemical Fire Extinguishers Work?

Potassium is the chemical element that is used in a . Potassium salts are created as a fine mist that is sprayed out and then causes a reaction so that a soapy layer is formed on the surface of the fire.

The mist is fine to not spread the burning oil and works to create a cooling effect and smother the fire.
What Are the Pros and Cons?

This is the sole fire extinguisher appropriate for a fire that involves cooking fat or oil.

Toxic fumes can be created when a is used. Hence the area needs to be very well ventilated after the fire has been put out.
Who Needs Wet Chemical Fire Extinguishers?

All premises that have a professional kitchen or fry foods should also have Such premises include the following:

How Do You Use a ?

Safety Notes:

A needs to be used very carefully as there is a risk of splashing burning fat or burning oil into the nearby areas.

Use the following steps to use a safely:

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