What are the 4 stages of fire?

In this article, we will be discussing the stages of fire. There are generally four stages of fire: incipient, growth, fully developed, and decay. Each stage has its own characteristics that will be discussed in more detail below.

Knowing the different stages of fire can help you better understand how to fight a fire, and what to expect during each stage.

4 Stages Of Fire

Who is not familiar with Fire..!! Fire can be considered a boon and curse of any type of industry. Fire is useful if it is used in a controlled manner. Fire is used in many places for the betterment of humans but if any abnormalities happen and somewhat situation goes out of control, it can be a curse and cause damage to lives and property.

To use fire we should be familiar with the Fire triangle and fire tetrahedron which is described by Chemical tweak in details. Fire is an integral part of industrial safety and learning industrial safety without fire in detail in not possible. Today in this tutorial we will learn fire in detail i.e what are the stages of fire.

Prior to knowing what are 4 stages of fire, let us refresh the basic definition of fire / what is fire?.

What is Fire?

A fire is typically defined as a rapid, persistent chemical reaction between a fuel and an oxidant accompanied by the production of heat and light. In order for a fire to occur, three things must be present: fuel, oxygen and an ignition source.

What are the stages of fire – What are the 4 stages of a fire?

As a fire broke out in any workplace, and if we breakdown a fire then this can be known there are 4 stages of a fire. International Fire Service Training Association (IFSTA) stated that there are 4 stages of fire. All the stages of fire are enlisted below

  1. Incipient
  2. Growth
  3. Fully developed
  4. Decay

Now let us learn 4 stages of fire in detail.

1. Incipient

Incipient is known as the first stage of fire. As the fire triangle elements like oxygen, fuel, and spark/heat combine with each other and continuous chemical reaction results is the breaking out of the fire. This incipient stage of fire is also known as ignition. This is the initial stage in which fire is in the smallest phase which provides the golden opportunity to take action and suppress the fire.

This is the stage in which the fire is at the initial level and one can take measures and stop the fire to get into another stage and one can avoid the fire accident. The thing that requires in this stage to suppress the fire is the detection of fire and quick action. Majority of time, fire can be suppressed easily but the breaking out of the fire is not detected in the incipient stage and hence quick and immediate action has not been taken.

The other reason why fire gets into another stage and results in a fire accident stage is a delay in action. Delays in firefighting action can cause fire to get the bigger stage and make the situation worse. There are a number of reasons that are responsible for delay in action and those are listed below

  1. Not availability of fire fighting equipment
  2. Not availability of fireman
  3. Lack of trained personnel /worker/employee

This incipient/ ignition stage is the golden chance to stop fire and avoid the conversion of small fire to dangerous fire incident.

2. Growth

Fire if not controlled at the initial/incipient stage then it converts to the second stage which is the Growth stage. in this growth stage of fire. During this stage, fire keeps on consuming combustible material as fuel and the presence of oxygen to multiply its growth and this result in the conversion of the fire stage from incipient to growth. This is the shortest and most dangerous stage as sometimes within a fraction of a second fire from just ignition turns into a huge fire. This stage is mostly responsible for the trapping of persons and firefighters.

3. Fully Developed

After the Growth stage of fire, when all the combustible material catches fire and the growth stage has reached its maximum potential that stage of fire is considered as fully developed.

The temperature at this stage is the maximum among all stages of fire and it is the dangerous stage for firefighters or personnel trapped in the affected site as leaving the affected site during this stage of fire is very difficult.

4. Decay

The last stage and longest stage of a fire is the decay stage. In this stage, all the fuel present at the site get burned or the presence of oxygen got decreases which result in the fire being put in the final point. Special observation and care to be taken in this fire stage also as the fire is stopped or getting slowed down by a reduction of fuel or insufficient oxygen.

There is always a chance that the oxygen gets rushed to the affected site and the fire get reinitiated. Another possibility is the presence of flammable presence of combustible material left as this left combustible material has the potential to initiate fire.

Graph of Stages of fire

Stages Of Fire
Graph of Stages of fire

To extinguish fire, there are Types of fire extinguishers are used, we had covered all the types in detail along with which type to use in different types of fire.

FAQ (stage of fire)

1. What are the 4 stages of fire?

National Fire Protection Association has classify fire in 4 stages. The NFPA and most other standards classify four stages of a fire.
1. Ignition.
2. Growth.
3. Fully Developed.
4. Decay.

2. What stage of a fire is the longest?

The longest stage of fire is the fourth stage, i.e. Decay.

Wrapping Up

Hope you like the article on Stages of fire and you know what are the 4 stages of a fire? If you had any confusion related to this article then feel free to use the comment section we will try to help you. Don’t forget to check out the industrial safety article if you have an interest in learning industrial safety in detail. If you had any suggestions or what us to cover any specific topic then let us know through the contact us section.

Avatar Of Ronak Prajapati

Me - Founder of Chemical Tweak - A Chemical Engineer by profession and a part-time self-trained technology blogger.

6 thoughts on “What are the 4 stages of fire?”

  1. Fire’s could also be classified into different phases such as; the incipient (first phase) of fire, the rollover phase (warm gases rise), Steady-State Burning Phase, the falshover phase (combustible vapor that’s exposed to the heat rapidly and simultaneously ignites), and lastly the smoldering phase (flames almost begin to die but the burned area is filled with heat and thick black smoke).

  2. Thanks for the good explanation I really enjoyed it. Kindly help me explain more on flashover make me understand


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