The Four Ways Fire and Smoke Can Spread

Fire can spread dangerously fast. In certain circumstances, it can take only minutes for a single, unsupervised flame to set a whole building alight.

A key part of fire safety awareness is understanding the ways in which fire can spread so that you also understand what can and should be done to prevent this. Fire spreads by 4 methods, and each of these can be tackled in a different way to help minimise the impact if a fire does break out.

In this article, we explain the four ways fire and smoke can spread and then cover the different approaches that can be used to stop fire from spreading.

What Are the Four Ways in Which Fire Can Spread?

There are four ways fire and smoke can spread once a fire begins. Below, we’ll explain each process and what causes them.

Conduction

Conduction is a scientific term that describes the transfer of heat through a material or between two materials that are touching. In fire safety terms, conduction is what happens when a fire spreads by heating up a material which then causes the materials next to it to ignite.

A common example of a conduction fire is if a fire starts and heats up something metal, like a beam. If this beam is touching something combustible, it will eventually grow hot enough that it heats up the combustible material and causes that to ignite.

With this type of fire spread, materials don’t need to be directly touching for them to catch fire. If they are joined in some way by another material that conducts heat well, this heat can spread the flame from one material to the other, causing the fire to spread over a distance.

Convection

Convection is the biggest cause of fire spread. The scientific term means the transfer of heat through a liquid or a gas, and in fire safety it refers to the way that a fire heats up the air around it, causing the hot air to rise and cooler air to take its place. This creates convection currents that cause heat and fire to spread to other areas.

As the hot air from a fire rises and spreads, it can cause other materials to ignite because of this heat. This means that the fire spreads very quickly and will continue to spread as the convection currents move heat around a space.

One reason why this is one of the common ways in which fire can spread is that heat, smoke and embers travel upwards. In multi-storey buildings, fire climbs from one floor to another and the whole building can quickly be consumed.

Radiation

With radiation fires, heat travels in the form of electromagnetic waves. It doesn’t require any direct contact for fire to spread; it just involves the air heating up enough that combustible materials get hot enough to ignite.

Heat can travel through electromagnetic waves in any direction, so fire can spread outwards from the original source in this way. If a material is particularly combustible, this means that it just needs to be in the same room as a fire to eventually ignite once the air grows hot enough.

Direct Contact

The last of the ways in which fire can spread is through direct contact. This happens when flames come into direct contact with a material and it ignites, which is most common amongst highly flammable materials like paper and wood.

Direct contact fires can also happen if a liquid or a gas catches fire, which can quickly lead to other materials also igniting considering how quickly fire spreads across things like oil or fuel. It’s a very common way fire can spread in environments where there are a lot of flammable materials around, such as places filled with paper, wood and fabric.

How Long Does It Take for a Fire to Spread?

It only takes 30 seconds for a fire to get going and begin to spread. Within five minutes, fire can spread in several ways and an entire house can have gone up in flames.

Understanding the different ways in which fire can spread can help you grasp why this can happen so quickly. If there are a lot of combustible materials close to each other, the air temperature is warm, and there are heat conductible materials in the building, the different types of fire spread can all happen at once and cause a fire to grow in size very quickly.

Slowing the spread of fire can not only ensure that buildings can be safely evacuated, but it also means that the overall damage that a fire does is lessened. When you know the four ways fire can spread, you can take preventative action to help limit these ways if a fire does happen.

How to Prevent a Fire From Spreading

Whether you’re responsible for fire safety in your workplace or you want to learn more about how to keep your home safe, knowing how to stop fire from spreading is very valuable. A combination of preventative measures and the knowledge of what to do if you discover a fire is the best approach to minimising how much a fire can spread if it starts.

Here’s a breakdown of some of the different measures that prevent fires from spreading. 

The Fire Triangle

Before we explain the different measures that should be taken to prevent fires from spreading, it’s important to consider the fire triangle and how this informs different approaches to fire prevention.

The three elements that make up the fire triangle are heat, fuel and oxygen. ​​To prevent a fire from spreading, one of the elements of the fire triangle needs to be removed.

A lot of measures that prevent fires from spreading focus on removing fuel and oxygen from the triangle to limit how much a fire can grow. By using fire-resistant materials, or containing fire in a space so that it eventually runs out of oxygen, these preventative measures utilise understanding of the fire triangle to avoid feeding fire and letting it spread.

Minimising Types of Fire Spread

Along with ways to remove an element of the fire triangle, you can also prevent fire from spreading by trying to minimise the different ways that fire can spread. 

An easy one of these is to avoid storing flammable materials together where they are touching, as this prevents fire by conduction and direct contact. You should also avoid having flammable materials touching anything that conducts heat like metal, either by storing them elsewhere or covering metal pipes and beams with fire-resistant material.

Make sure to keep flammable materials away from any machinery that emits heat to avoid fire starting through radiation. You should also try to keep spaces with heat-emitting machines cool with air conditioning to decrease the likelihood of a fire starting because of this heat.

Passive Fire Protection

Passive fire protection, or PFP, is an approach to fire safety that uses a range of systems to prevent fire spread through a building. It works by compartmentalising a building into small spaces where fire would be contained if it started, which helps to stop it from spreading and causing more damage.

Fire doors are a key part of passive fire protection, designed to withstand really high temperatures and made of fire-resistant material that keeps fires and smoke contained when they are properly sealed. Fire doors either remain closed or are designed to shut when the fire alarm goes off, so must be kept clear at all times if they are going to successfully be able to prevent the spread of fire.

Cavity barriers and fire compartmentation are also used to seal over gaps and openings with fire-resistant materials. This stops fire, and importantly smoke, from spreading through things like ducts and cavities, which can massively limit how much a fire and fumes grow through the building.

Another aspect of passive fire prevention is creating routes to safety that are also protected by fire-resistant materials. These will offer the fastest routes to safety between areas where fire has been contained, marked up with appropriate signs and glow-in-the-dark markers to help everyone get to safety as fast as possible.

Active Fire Protection

Active fire protection, or AFP, involves some form of action to tackle the spread of fire. It should be used in combination with passive fire protection and involves a range of firefighting and fire evacuation techniques.

The arguably most important aspect of active fire protection is appropriate fire safety training. This ensures that people have the information they need to respond to fires, stop them from spreading and keep themselves safe, whether this is knowing what to do when a fire alarm rings or being trained to use a fire extinguisher. In the workplace, fire safety training should also include appointing a fire warden to schedule fire drills and oversee fire drills and evacuations

Fire evacuation procedures are also an important part of active fire protection, although this has less of a direct impact on preventing the spread of fire. However, part of the evacuation process might involve keeping fire doors shut or tackling small fires when it is safe to do so, which can minimise how much a fire grows.

Finally, one of the most active measures that prevent fires from spreading is using a fire extinguisher or other fire fighting equipment. This should only be done if the person using the equipment is trained and the fire is small enough to safely fight. Otherwise, the fire service should be called to come and deal with the fire instead.

FAQs

Does smoke spread faster than fire?

Smoke tends to spread faster than fire, especially when the fire is very hot. Smoke can fill a space even when the fire is only happening in a small part of it, which is why smoke can be so dangerous before a fire has even really started to spread.

Do fire doors prevent the spread of smoke?

Fire doors prevent the spread of smoke as well as fire, which helps to keep the spread of fire contained. Fire doors will eventually stop working, but this is usually after at least 30 minutes which should be enough time to properly evacuate if the correct procedures are followed.

During an emergency, what should you do if the fire is large and spreading rapidly?

In an emergency, the main priority should be to get yourself and the people around you away from the spreading fire as quickly as possible. This should involve raising the alarm so that everyone is aware that there is an emergency, calling the emergency services as quickly as you can safely do so, and evacuating the building to keep everyone safe.

Summary

Fire can spread in several ways, and each of these can contribute to the rapid spread of danger throughout a building. The slower that a fire spreads, the more time people have to evacuate and the less damage that is likely to be done. Therefore, knowing the ways fire can spread means you can help to prevent these scenarios and help to keep the risk of fire and fire damage to a minimum.

If you’re looking for more information on how to stop fire from spreading through preventative measures, we cover this topic and much more in our online ‘Fire Safety Training’ course, which can help to ensure compliance with fire safety regulations in the workplace.