Fires can have a devastating impact on anything that they encounter, but what exactly are the four different stages of a fire?
There is more to a fire than simply burning, and these 4 stages can help firefighters to identify the full extent of the situation and come up with an efficient plan of action.
Of course, all fires are extremely dangerous, but it is important for firefighters to think about what they are walking into, so that they can take the best precautions. It also helps them to know what risks and challenges they are more likely to face at each stage.
In this article, we are going to explain each of the four stages of a fire, so you can better understand what it all means. We are also going to look at the importance of each stage, and what categorizes each of the stages.
If you want to find out more about the stages of a fire, just keep reading.
Why Are There 4 Stages of a Fire?
The main reason why there are four stages of a fire is that it helps firefighters to identify what stage the first is at.
These stages are taught to firefighters in training, and they will first assess the stage that the fire is currently at, which allows them to respond accordingly. Depending on the state that the fire is in, the firefighters will be able to assess things like:
- How the fire is most likely to act and how it might progress
- How much of a risk the fire poses to both firefighters and civilians
- What the best way to extinguish the fire would be
To help you to better understand the four different stages of a fire and what happens in each stage, we are going to provide you with some more detailed information below. We will also look at the dangers that each stage poses.
The 4 Stages of a Fire
Now that you know that there are four stages of a fire, you are probably wondering what they are. The 4 stages of a fire are:
- Fully Developed
The incipient stage of the fire is the first stage of a fire, and this stage occurs immediately after ignition. This would mean that the fire has only just started, and it can be identified from the following factors:
- The fire has not yet affected anything beyond its immediate vicinity
- The smoke has not yet reduced visibility in the vicinity, and people inside are still able to breathe
- People in the area will be able to escape without too much difficulty
- The heat level of the fire is quite low
- The smoke alarm is sounding
Something else that characterizes this stage of a fire is its liminality or uncertainty. The fire is at the point where it could either extinguish and avoid destruction, or it can establish itself and start to spread out of control.
Whether the fire in the incipient stage is extinguished has to do with factors such as:
- Any flammable fuels that are in the area
- The access that the fire has to oxygen
- Whether there are people nearby that can put out the fire
An incipient fire can usually be extinguished easily with the use of fire safety equipment that you might find in a house, like a fire extinguisher or safety blanket. The fire brigade should be called straight away and people should leave the area.
Examples of an Incipient Fire
- A candle that has been left unattended and has tipped over on a surface. The flames are just teetering on the top of the surface. If there are other flammable objects on the table, this could cause the fire to enter the next stage.
- A cigarette that has dropped onto a coach. The couch is just starting to smolder, but there is still time for the person to pick it up and smother the fire to prevent it from spreading.
- An electrical fault causes a stove to catch fire due to an electrical fault. The stove’s fail-safe is triggered and the fuse blows, allowing the fire to extinguish all on its own.
- A wildfire ember has made its way from a fire and landed in a backyard, lighting up a few dried leaves in the place where it landed.
The growth stage of a fire will occur once the fire has established itself, and it has started to burn self-sufficiently. At this stage in time, the fire will be generating enough of its own heat to cause a positive heat feedback loop.
This means that the fire has the ability to use its own heat to cause combustion of surrounding fuel sources.
At this stage, the fire will be able to spread around the area and destroy anything in its path. The best ways to identify this stage of a fire include:
- A layer of smoke that is visible above the fire. If the fire is inside, you might notice that the smoke is now accumulating in the top two feet of the room
- The temperature in the room will have significantly increased
- Any windows might start to turn brown around the edges, and they could also start to crack. You will no longer be able to see any condensation on the windows
This stage of a fire is actually the shortest stage of a fire, and is where the flames will start to spread quite quickly. This stage is very dangerous, and people can easily become trapped in the building and require rescue.
The growth stage of a fire will usually be over one a flashover occurs, which is the point in a fire’s life where it has generated so much heat that the fuels in the vicinity will all catch fire spontaneously. The heat will usually be around 1150 degrees Fahrenheit before this occurs.
During a flashover, you are likely to see a flash, and this is when the fire spreads so quickly that it can engulf a room in an instant. A flashover is very dangerous, and it can trap and burn both people and firefighters that are in the home.
Fully Developed Fire
The fire will become fully-developed once it has reached its hottest point. At this stage in time, it will be engulfing all of its fuel sources. The intensity of the fire is likely to decline at this stage unless a new fuel source is added.
A new fuel source can even include something as simple as a change in wind conditions.
This means that this is still the most dangerous stage in a fire’s life, and this is where it is at its hottest and most aggressive stage. When the fire is fully developed, people should be staying as far away from the fire as possible.
It can be almost impossible to escape the fire at this stage if there are any remaining survivors, and rescue is the most likely escape option.
However, at this stage of a fire, firefighters will usually try to take on the fire from a distance. They will also try to undertake fire reduction practices, which include things like back burning. This ensures that new fuels are not being introduced to the fire.
The final stage of a fire is the decay stage, and this is when the fire will run out of oxygen or fuel, so it cannot sustain itself.
This is typically the longest stage of the fire, and for larger fires like wildfires, it can take several weeks for this to happen. It would not take a sling in a house fire, but it can still last for a significant amount of time.
Another big danger of the decay stage is the potential for new oxygen or fuels to be introduced into the fire. Something as simple as a sudden wind updraft of a falling tree branch can lead to the fire reigniting.
Once the fire has burned out, thorough care must be taken to ensure that the fire does not go up again.
The structural integrity of any buildings or trees that have been on fire will be compromised, which can lead to injuries from collapsing structures. The fire can still also have many carcinogens that are dangerous to both people and animals that are in the area.
Fires have four different stages, and they will make their way through each of them. A firefighter will usually assess the stage that the fire is at when they arrive at the scene, and this is so they can be aware of the most likely behavior of the fire.
This will help them to know what the best approach is when it comes to trying to tackle and extinguish the fire. Every single stage of a fire is dangerous, as all of them can change and adapt very quickly.
This is why it is so important to evacuate if a fire cannot be extinguished with ease. If you are ever in a fire, call the fire brigade immediately.