Understanding the science behind a fire is just as important as understanding what extinguisher to use to suppress it and how to reduce the risk in the future. Fire is unpredictable by its very nature, and that’s why fully developed fires should only ever be fought by professionals or those with recent fire training.

Knowing what to do in the event of a fire can make all the difference, but it’s vital that you also understand how a fire starts, how to control it, and how to prevent it from happening again.

Undoubtedly, one of the trickiest aspects to understand, whether you’re an industry professional or just someone who lives or works around fire risks, is the fire tetrahedron. This is a relatively new term and is similar to one you may already know about – the fire triangle. The fire tetrahedron is proof that knowing the science behind a fire is as vital as knowing what to do if one starts.

Today, we’re going to break down the different elements of the fire tetrahedron, explain how it’s different to the fire triangle and provide practical tips for you to use in your fire safety strategy.

What is the fire tetrahedron?

An adaptation of the fire triangle, the fire tetrahedron takes its name from the geometrical shape composed of four triangular faces. Each of the four sides in this model represents one of the four essential elements required for fire to occur and, importantly, continue burning: heat, fuel, oxygen and a chemical chain reaction.

If even one of these elements is removed, the fire will go out.

The simplest way to remember it is that:

• The fire triangle helps us understand how a fire starts
• The fire tetrahedron helps us understand how a fire continues and how to stop it

From fire triangle to tetrahedron: what’s changed?

The fire triangle (consisting of heat, fuel and oxygen) has long been described as the known method required for a fire to start, but the addition of the chemical chain reaction is reflective of modern fire risks and sophisticated suppression tactics (such as Lithium-ion battery fires and specific ways to suppress and extinguish them).

The fire triangle was used for many decades and taught in schools as well as in training for fire safety professionals, and it has served its purpose. However, a deeper understanding of the science behind fires has developed our understanding beyond the fire triangle.

Research revealed that in a fire, there are particles known as ‘free radicals’ that are generated by combustion, which enable a fire to keep going via a chemical chain reaction, even when the original ignition source (heat, oxygen or fuel) is removed.

This led to the adaptation of the term ‘fire tetrahedron’.

Breaking down the four elements of the fire tetrahedron

As touched on already, four elements make up the fire tetrahedron, and we’ll look at each in a little more detail here:

• Heat: Every fire needs a source of ignition, whether it’s a spark, open flame or a high ambient temperature. This is the trigger that starts the fire and helps it to spread.
• Fuel: This is the substance that burns, and is any form of combustible material. It could be a literal fuel, such as petrol, but could also be wood, paper, flammable liquids and gases, or Lithium-ion batteries.
• Oxygen: This is what ‘feeds’ the fire. It’s naturally present in the air around us, meaning you don’t need to see its presence for it to be involved.
• Chemical chain reaction: This is the newest and most complex component, and as we’ve talked about, the reason the fire triangle has evolved into the fire tetrahedron. Once the fire is burning, a series of chemical reactions occur between the heat, fuel and oxygen. These reactions can keep feeding the fire, even if the source (such as the fuel, i.e. wood) has been removed.

How to stop a fire: disrupting the tetrahedron

To extinguish a fire, the practicalities of the fire triangle remain true, with the addition of the fourth component of the fire tetrahedron. Depending on the type of fire, here’s how to stop the fire by removing one of those elements:

• Remove the heat. Use a water extinguisher to cool the fire (Class A only)
• Remove the oxygen. Use CO2 extinguishers to displace the oxygen and smother flames (Class B or C only). Foam extinguishers also remove access to oxygen by creating a seal on the top of the burning liquid (Class B only)
• Remove the fuel. If it is safe to do so, shut off the supply of flammable gas or liquid
• Interrupt the chain reaction. Use a Lith-Ex extinguisher or Pyrocloud to break the chemical reaction process at a molecular level

At Firechief® Global, you’ll find a range of fire fighting equipment suitable for disrupting the fire tetrahedron, including PyroFlow fire suppression granules to smother the flames, fire extinguishers to remove the heat or interrupt the reaction, and fire blankets to stop the flow of oxygen.

Understanding the fire tetrahedron is important for us all to know how a fire continues and what to do to stop it. However, it is not just a theoretical concept; it is a practical one and informs:

• Fire extinguisher selection. Knowing which fire extinguisher to use to put out the fire
• Fire risk assessments. Ensuring that all steps are taken to prevent and stop a fire
• Evacuation planning. Making sure you have functioning alarms and have safe routes out of a building
• Regulatory compliance. Understanding what is needed from a legal standpoint
• Staff fire safety training. Giving staff the knowledge and understanding they need to tackle a fire safely and effectively.

In addition to our Lithium-ion battery fire extinguishers and blankets, the Firechief® range of fire safety products also includes extinguisher stands, suppression systems, signage and fire safety products for all types of fires. For information, call us on +44 (0)330 999 0019 or email sales@firechiefglobal.com.

To stay up-to-date with more product news and insights from across the fire safety industry, follow Firechief® Global on LinkedIn.

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Disclaimer

The information contained within this blog is provided solely for general informational and educational purposes and is not intended as a substitute for professional advice. Before taking any actions based upon this information, we advise the reader to consult all relevant statutory or regulatory guidance and, where necessary, to consult a qualified fire or industry regulation professional. The use or reliance on any information contained herein is solely at the reader's risk.