5 Major Classes of Fire You Should Know

Fire is the rapid oxidation of a material in the exothermic chemical process of combustion, releasing heat, light, and various reaction products. Fire is grouped into classes based on the source of its fuel. This is the area of concentration for this article; Classes of Fire.

We have 5 major classes of fire which you will see in the next paragraph.

How Many Classes of Fire do we have

There are majorly five (5) classes of fire according to the National Fire Protection Association. Electrical fires are not categorized among the classes, you will see reasons as you keep reading.

1. Class A Fires: Fires in ordinary combustible materials, such as wood, cloth, paper, rubber, and many plastics.
2. Class B Fires: Fires in flammable liquids, combustible liquids, petroleum greases, tars, oils, oil-based paints, solvents, lacquers, alcohols, and flammable gases.
3. Class C Fires: Fires that involve energized electrical equipment.
4. Class D Fires – Fires in combustible metals, such as magnesium, titanium, zirconium, sodium, lithium, and potassium.
5. Class F Fires (Class K Fires) – Fires in cooking appliances that involve combustible cooking media (vegetable or animal oils and fats).

• Electrical Fires – These types of fires involve live electrical apparatus. (Technically ‘Class E’ doesn’t exist however this is used for convenience here)

Class A Fire

Class A fires are fires involving solids, i.e., they use solid fuels. Examples could be paper and cardboard, common in offices and manufacturing. It could be furniture, or fixtures and fittings. It could even be the structure of the building.

Class A fire is one of the most common types of fire because solids are the most common type of fuel and one that is hard to eliminate.

Good housekeeping will help to keep materials like packaging and waste reduced, minimizing risks.

The only type of fire extinguisher that should be used on a class A fire is the water extinguisher.

Class B Fire

Class B fires are fires involving flammable liquids and gases. Many of the fluids, liquids, and chemicals used in workplaces can be flammable or explosive. Like cleaning fluids, solvents, fuels, inks, adhesives, and paints.

According to statistics, in 2010/11 flammable liquids accounted for only 2% of fires, but a massive 21% of fatalities. These fires are less common than class A fires but more deadly than other types of fire.

Class B fires can be extinguished using foam or powder Fire extinguishers.

Class C Fire

Class C-rated extinguishers can put out fires that involve energized electrical equipment. There are no numerical components for Class C ratings of extinguishers, we only care about the conductivity of the fire extinguisher. Are you at risk of being shocked when using this extinguisher on energized equipment?

To get the C rating the extinguishers are tested to see if any electrical current flows through them as they are discharged on energized electrical equipment. You won’t see an extinguisher with only a C rating, they will always have an A and/or B rating as well. (When electrical equipment is de-energized, extinguishers rated for Class A or B fires are used.)

Class D Fire

Metals are not often thought of as a combustible material, some types of metal can be, like sodium. Metals are also good conductors, helping a fire spread. All metals will soften and melt at high temperatures, which can be a big problem when metal joists and columns are present in a fire as structural elements.

Water can act as an accelerant on metal fires. class D fire can be tackled using dry powder extinguishers. The powder inside the extinguisher may vary depending on the type of metal risk it is designed for. Small metal fires can sometimes be smothered with dry earth or sand.

Class F Fire

Deep fat frying and spillages of flammable oils near heat sources in kitchens can result in a class F fire.

Never leave food or frying equipment unattended during use. The only type of fire extinguisher approved for use on cooking oils and fats is the wet chemical extinguisher. For small class F fires, you could also use a fire blanket.

Electrical Fires

This is not strictly a class of fire, because electricity is more of a source of ignition than a fuel. This is why most quarters exclude electrical fires as a class of fire.

However, fires in live electrical equipment are an additional hazard. You do not want to be using water, or any other conductor as that could be fatal.

NOTE: According to the “The Fire Safety Advice Centre ” Electrical fires are not given their full class, as they can fall into any of the classifications. After all, it is not the electricity burning but the surrounding material that has been set alight by the electric current.

You can use carbon dioxide, and dry powder extinguishers in low-voltage situations. Always turn off the power supply if you can.