Using a Wet Chemical Fire Extinguisher

Fires are dangerous, and can cause harm to life and property. All homes and businesses should have the appropriate fire extinguishers close by and up-to-date to ensure the safety of residents and employees in buildings in the event of a fire.

There are different types of fire extinguishers, as per Australian standards, and wet chemical fire extinguishers are one of them. Even though wet chemical fire extinguishers are relatively niche in Australia due to their limited uses, they serve a vital purpose in certain situations i.e. kitchen fires. This guide will review the functions of a wet chemical fire extinguisher, what to do in the event of a fire, how to use them appropriately in fire emergencies, and their essential safety maintenance.

What Identifies a Wet Chemical Fire Extinguisher?

A fire extinguisher typically has a ‘signal red’ tank for easy identification. Wet chemical fire extinguishers have this colour as well. However, the significant difference between a regular fire extinguisher and a wet chemical fire extinguisher is the prominent oatmeal coloured band, or a band of dull yellow colour which is wrapped around the cylinder’s top half.

Aside from its band, there are other ways to identify a wet chemical fire extinguisher. For instance, you can determine the type by observing the tank itself and looking at the description label on the back of the tank. The extinguisher should include the size, instructions for use, safe materials to use on, attached maintenance tag, and a wall bracket for mounting.

You can keep in mind that wet fire extinguishers are available in two main sizes:

2 Litres fire extinguisher size which weighs between 4-5 KG and has a discharge time of around 30 seconds.
7 Litres fire extinguisher size which weighs between 12-13 KG and discharges from 40-50 seconds.

What Are Wet Chemical Fire Extinguishers Used For?

Firefighters use wet chemical fire extinguishers for two classes of fires: Class A & Class F.

Class A fires typically consist of ordinary combustibles that can catch fire. These carbon based solids include plastics, wood, paper, and textiles.

As for Class F fires, they include fires that start from fats and cooking oils, typically in fryers. You can use a wet chemical fire extinguisher for homes, commercial kitchens, restaurants, cafes, and food processing factories that may use cooking oil or fat.

While wet chemical fire extinguishers work for Class F fires, there are classes that this type of extinguisher may not work effectively on:

Class A Fire: These deal with flammable materials. While a wet chemical extinguisher is sufficient for this type of fire, you can also use ABE fire extinguishers, water fire extinguishers or foam fire extinguishers here.
Class B Fire: Class B fires typically deal with flammable liquids such as oil-based paints, solvents, alcohols, and more. A dry chemical powder extinguisher, foam fire extinguisher or in some cases, even a carbon dioxide fire extinguisher could be an option for this type of fire in some cases.
Class C Fire: Class C fires deal with flammable gases. A dry powder extinguisher with a C rating may be able to put out such fires.
Class D Fire: Class D is for flammable metals such as lithium or potassium. A separate powder fire extinguisher with class D rating works for this class of fire.
Class E Fire: Class E Fires deal with electrical equipment. You can use carbon dioxide-based fire extinguishers for electrical fires.

How Do Wet Fire Extinguishers Work?

Even though there are different types of fire extinguishers, they all work on the concept that fire needs three key elements to combust and sustain itself: fuel, heat, and oxygen. The primary goal of fire extinguishers is to put out the fire by removing one or more of them.

Wet chemical fire extinguishers consist of an extinguishing agent which is a solution of potassium and operates by creating a barrier between the fire and oxygen in the air and preventing reignition while also removing the element of heat.

One of the primary ways to ensure that you use your wet fire extinguisher efficiently is to follow the PASS technique:

P- Pull the pin
A - Aim low
S - Squeeze the trigger
S - Sweep or swing the nozzle from one side to the other

Cleaning Up After a Wet Chemical Fire Extinguisher

Once you are finished, and the situation has been resolved, wet chemical extinguishers leave a residue you must clean. Be mindful of the discharge effects of the extinguisher:

Cover your eyes and hands with protective gear, as the extinguishing agent can irritate the throat, nose, ears, and hands.
Wet chemical fire extinguishers tend to leave a corrosive residue [alkaline substance] that can damage other materials [e.g. aluminium].
Do not wash the wet chemical extinguishant down the drain, as it can harm the environment. You should soak the area with paper towels, then wash the residue away. Afterward, discard the used paper towels in a plastic bag in regular waste bins.

Maintenance of Wet Chemical Fire Extinguishers

Maintain the upkeep of your wet chemical fire extinguishers every 6 months and consult a fire safety testing & maintenance service. The extinguishers should have a maintenance tag with the most recent inspection date marked. Also, every five years, a professional should discharge and recharge your fire extinguisher and perform hydrostatic testing.

Here are the steps in the refilling process:

Depressurize and empty your wet fire extinguisher.
Refill the extinguisher with the chemical.
Check for leaks, then repressurize the extinguisher.
Reconnect the extinguisher’s ring pin and hose.
Weigh the extinguisher to ensure it's filled up correctly, then store it in a cool, ventilated area.
Dispose of any expired extinguisher as per local recycling rules.

Prioritise Fire Safety

Wet chemical fire extinguishers are effective fire extinguishers with limited uses in fire protection. Even if you can handle this extinguisher, only trained individuals should use it for emergencies.

Lastly, reach out to fire safety services in Geelong for regular inspection, testing, and maintenance of fire equipment as they are a must for fire protection. Knowing what type of fire extinguisher to use and the steps to take in the event of a fire can help keep you and the people around you safe.