What are the Different Classes of Fires?
Fires come in many forms, so you need to identify thee classes of fire to properly and swiftly extinguish whichever type of fire you face. Let’s look at a summary of the 6 classes of fire:
- Class A – Fires that involve solid or organic materials, such as wood, plastics, paper, textiles, or coal.
- Class B – Fires that involve flammable liquids, such as gasoline, petroleum oil, paint, or diesel.
- Class C – Fires that involve flammable gases, such as propane, butane, or methane.
- Class D – Fires that involve combustible metals, such as magnesium, lithium, sodium, potassium, titanium, or aluminium.
- Class F – Fires that involve cooking oils and fats, such as vegetable oil, sunflower oil, olive oil, maize oil, lard, or butter (typically those used for deep-fat fryers).
- Although it is not recognised as a separate class of fire in Europe, electrical fires that involve live equipment and electrical sources are also a type you should bear in mind (think of it as an informal Class E; ‘E’ for electric to help you remember).
Class A | Solid or Organic Materials
Fires that involve solid or organic materials, such as wood, plastics, paper, textiles, or coal.
Perhaps the most common types of fire, it is hard to eliminate the risk completely. This is due to the fact that many everyday materials can act as a solid fuel. Forward planning and proactive housekeeping should help to keep combustible materials like packaging and waste reduced, minimising risks.
The only type of fire extinguisher you should use on a class A fire is the water extinguisher.
This is the most popular type of extinguisher because it can handle most fires involving solids. But, as a conductor, it should never be used near electrical equipment.
Suitable Fire Extinguisher | Water
Class B | Flammable Liquids
Fires that involve flammable liquids, such as gasoline, petroleum oil, paint, or diesel.
Many of the fluids, liquids and chemicals used in workplaces can be flammable or explosive. Like cleaning fluids, solvents, fuels, inks, adhesives and paints.
It is important to identify what flammable liquids are used in your workplace, this can be done via a fire risk assessment. This process will help you clarify the locations, quantities and nature of the flammable liquids within a premises or site. You may need to compliment your fire risk assessment with a COSHH assessment to ensure employee safety.
Suitable Fire Extinguisher | Foam
Class C | Flammable Gases
Fires that involve flammable gases, such as natural gas, LPG or other types of gases forming a flammable or explosive atmosphere.
Working with with gas is can expose people to significant risk, including the risk fo fire/explosion. Stored gases must be kept sealed containers in a secure storage area.
Before you attempt to tackle a flammable gas fire, the first critical step is to ensure the gas supply is shut off before any action is taken.
Powder fire extinguishers are the best option for gas fires, however it is often best to shut the supply off if safe to do so, then move to a safe area before taking direction from the emergency services.
Suitable Fire Extinguisher | Powder
Class D | Combustible Metals
Fires that involve combustible metals, such as magnesium, lithium, sodium, potassium, titanium, or aluminium.
Understandably, metals are not commonly viewed of as a combustible material. In fact, depending on the physical state of the metal, they can be. Importantly, metals are also excellent conductors, and therefore a fire spread through transfer of heat. Eventually, metals will reach their melting point, which can be catastrophic for structural features of buildings.
Again, powder fire extinguishers are the most appropriate to be applied to metal fires.
Suitable Fire Extinguisher | Powder
Class F | Cooking Oils & Fats
Class F – Fires that involve cooking oils and fats, such as vegetable oil, sunflower oil, olive oil, maize oil, lard, or butter (typically those used for deep-fat fryers).
With overheated edible fat and cooking oil, there is a high risk of re-ignition, which often leads to serious injuries.
Fat burns should never be extinguished with water as water is lighter than burning fat. In a quenching test with water, the extinguishing water would quickly sink in the burning fat and evaporate. The resulting water vapor would suddenly shoot up and take the hot fat with it, creating a jet flame.
Suitable Fire Extinguisher | Wet Chemical
Class E | Electrical
Class E – Fire that involve electrical circuits, equipment or components
This is not strictly a class (class E) of fire, because electricity is moreso of a source of ignition than a fuel. However, fires in live electrical equipment are an additional hazard. You don’t want to be using water, or any other conductor as that could be fatal.
Making sure electrical equipment and installations are installed correctly, and inspected and maintained, will help to reduce the risk of this type of fire.
Suitable Fire Extinguisher | Carbon Dioxide (CO2)