The Fire Triangle Explained

Posted in Fire Safety Training on 31 May 2017

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Whilst a simple concept, the fire triangle (or combustion triangle) is a scientific principle that is important for all people to be aware of. Understanding how fires sustain themselves is essential background information in situations where you may have to use fire safety equipment. In this article, we will be summarising the fire triangle, and the lesser known fire tetrahedron, in order to give you vital insight into what maintains a fire.

What is the Fire Triangle?

The fire triangle, or combustion triangle, is the three components needed to ignite and sustain a fire. The three ingredients of a fire triangle are; heat, fuel and oxygen.

Fire Triangle

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If just one of these components is removed, the fire triangle will collapse and the fire will be extinguished.

Let’s explore these components in more detail:

1. Heat

A source of heat is required in order for ignition to occur, and different materials have different ‘flash points’ e.g. the lowest temperature at which they ignite.

Unfortunately, combustion reactions also produce heat as they burn, further increasing the temperature of the fuel. For some types of fire, the heat can be cooled with the application of water.

2. Fuel

A fire cannot begin if there is no material to burn. Homes and businesses are full of flammable materials, such as paper, oil, wood and fabrics. Any of these can serve as a fuel for a fire.

Some materials burn more easily than others. Fuels are probably the most difficult ‘side’ of the fire triangle to remove, so it’s wise to store them appropriately to prevent them becoming a fire hazard.

3. Oxygen

To sustain the combustion reaction, oxygen (or an oxidising agent) is needed, as it reacts with the burning fuel to release heat and CO2. Earth’s atmosphere consists of 21% oxygen, so there is plenty available to trigger a fire if the other two components are present.

Fire blankets and certain fire extinguishers remove the oxygen ‘side’ of the triangle by removing it or displacing it, causing suffocation and thereby ceasing the combustion reaction.

Fire Triangle Facts

  • Normal air contains 21% oxygen.
  • Fuel may also contain oxygen
  • Heat sources include: the Sun, hot surfaces, sparks, friction and electrical energy.
  • Fuel sources can be a solid, liquid or gas.

What is the Fire Tetrahedron?

The fire tetrahedron is a slightly more complex model to describe the components needed to ignite and sustain a fire. It is a four-sided geometric representation of the four factors necessary for fire:

Fire Tetrahedron
  • Fuel – any substance that can combust
  • Heat – heat energy sufficient to cause ignition
  • Oxidizing agent – air containing oxygen
  • Chemical chain reaction – sufficient reaction energy to produce ignition

Fire Tetrahedron Explained

The fire tetrahedron includes the three components covered in the fire triangle, with the addition of a chemical chain reaction.

This model is simply adding another dimension onto the traditional fire triangle model by treating the chemical reaction as its own separate component. Some fire extinguishers work by applying extinguishing agents to the fire to inhibit the chemical reaction on a molecular level.

Here at Fire Action, we’re committed to providing industry-standard fire safety equipment to homes and commercial clients across the South East region. With a huge range of fire extinguishers, alarm systems, and other products available, you can be sure to find the equipment that’s suitable for your premises. Contact us today to chat to one of our friendly advisers.


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