Fire Extinguisher FAQs

Below is a collection of Frequently Asked Questions about Fire Extinguishers and Fire Extinguisher Servicing.

Why are there so many types of fire extinguisher?

There are many types of fire extinguisher because there are many different types of fire. Each extinguisher is designed to be used on a specific class of fire. It is important to use the right extinguisher to ensure that your actions are as effective as possible and don't further ignite the fire.

What are the Classes of fire?

Class A - fires involving solid materials such as wood, paper or textiles

Class B - fires involving flammable liquids such as petrol, diesel or oils

Class C - fires involving gases

Class D - fires involving metals such as potassium or magnesium

Class E - fires involving live electrical apparatus*

Class F - fires involving cooking oils such as in deep-fat fryers

* Technically ‘Class E’ doesn’t exist. Before this classification system, there was a classification of electrical fires, but since electricity itself is a cause of fire, these types of fires have been incorporated into the main classes. Once you have turned off the electricity the fire becomes the same as any other.

What chemicals are used in a fire extinguisher?

Different chemicals are used for each different type of fire.

Dry chemical extinguishers use a powder-based agent which prevents chemical reactions involving heat, oxygen and fuel, this extinguishes the fire. The substances used for this are Monoammonium phosphate, sodium bicarbonate, potassium bicarbonate, potassium chloride and sodium bicarbonate based dry chemical (Foam compatible).

Foam extinguishers use an aqueous film forming foam, alcohol-resistant foams, film-forming fluoroprotein and a compressed air foam system. These smother the fires and prevent oxygen from fuelling it.

Water extinguishers use water to cool the burning material. This can be pump type water, air pressurized water and water mist

Wet chemical and water additives extinguish a fire by forming a soapy foam blanket over burning oil and cooling the oil down below its ignition temperature. They use wetting agents, antifreeze and loaded stream (an alkali metal salt solution which when added to water lowers its freezing point).

Carbon Dioxide extinguishers put out fires by displacing oxygen and removing heat from the combustion zone. They use halocarbon replacements, CO2, novec 1230, potassium aerosol and E-36 cryotec.

WATERMIST – there are no chemicals in the water mist extinguisher, it does, however, contain water. What makes water mist different or standard water extinguishers is the nozzle on the extinguisher disperses ‘dry’ water mist particles at a microscopic scale (ranging from 50 to 300µm, 50µm (micrometres) is 5/100ths of 1millimeter).

What are the different colour codes on fire extinguishers?

Fire extinguishers have colour codes labelling the type of extinguisher they are. These are represented on a band at the top of the extinguisher. Their purpose is to make identification easier and faster for the user. These codes are as follows:

Each extinguishing medium is assigned its own colour code:

Red for water, cream for foam, blue for dry power, and black for carbon dioxide. A fifth colour, yellow, is added for the new Wet Chemical type of fire extinguisher.

Are any fire extinguishers all purpose?

There aren’t any all-purpose fire extinguishers yet however, dry chemical extinguishers can be used on the majority of fires with a few exceptions.

What type of fire can each extinguisher be used on?

Dry chemical extinguishers can be used on all fire except oil fires (class F fires)

Foam extinguishers are best used on combustible materials (class A) and flammable solids and liquids (class B)

Water extinguishers can only be used on combustible materials such as wood, paper, cloth, trash, and plastics (class A)

Wet chemical extinguishers can be used on combustible materials (class A) and oil fires (class F). These extinguishers have been specifically developed to tackle fires involving cooking oils and fats and contain potassium salts which both cool the flames and smother the fire’s oxygen content.

CO2 extinguishers can be used on flammable liquids (class B) and electrical fires.

Fire extinguishers with a Class C rating are suitable for fires in “live” electrical equipment. Both monoammonium phosphate and sodium bicarbonate are commonly used to fight this type of fire because of their nonconductive properties.

What happens if you use the wrong fire extinguisher?

Using the wrong extinguisher could make matters worse; water on an oil/electric fire would cause the fire to get bigger. It’s safer to make sure you use the correct one.

What happens if you’re accidentally sprayed with a fire extinguisher?

If you are accidentally sprayed then check the bottle of the fire extinguisher for any health warnings, some may be irritants and if you really are worried you could go see a doctor. However, with most, it would probably just be a bit annoying, (pressurized water – you’d just get wet). The extinguisher should just rinse/dust off with minimal issues.

How long do fire extinguishers last?

Fire extinguishers last between five and 15 years but they all ultimately expire and become ineffective, no matter what fire-fighting substance they contain. Household fire extinguishers - which are filled with dry chemicals (carbon dioxide or halon) lose their charge over time.

How do you repair a fire extinguisher?

DON’T!

It could cause injury due to the high pressure if you have a damaged fire extinguisher call a professional to replace it.

How do you refill a fire extinguisher?

It’s safest to find a professional to refill your fire extinguisher as chemicals can be hard to find and the pressure may cause an accident. If the extinguisher has instructions for a refill then you can follow them as safely as possible. You can get replacements or send it to a professional to refill.

How often should fire extinguishers be serviced?

Fire extinguishers must be serviced every 12 months or after each use by a BAFE SP203 certified service provider. If an extinguisher is found to be leaking, it should be serviced immediately.

How to dispose of fire extinguisher?

Release any pressure contained in the fire extinguisher canister by shooting a small amount into an open area.

Let the canister sit for a few days, making sure the pressure has been released. Once there is no longer any pressure, please dispose in a black bin bag.