This poster is showing 3 models for the same thing - what fire needs to exist. Each model adds more detail, so you get better at preventing and stopping it.

 This poster is showing 3 models for the same thing - what fire needs to exist. Each model adds more detail, so you get better at preventing and stopping it.

The big idea at the top

Same goal - to explain what is needed for fire, but with more detail as we go. More elements = more understanding = better prevention and control.

1. FIRE TRIANGLE - The basic elements of a fire

This is the classic model. 3 sides, 3 elements. If you remove any one, fire cannot start or cannot continue.

1. Fuel: anything that burns. Solid like wood, paper, cloth. Liquid like petrol, diesel, oil. Gas like LPG, methane.

2. Heat: the ignition source. Spark, flame, hot surface, friction, electrical fault.

3. Oxygen: usually from air. Normal air is ∼21% oxygen. Most fires need at least 16% to keep burning.

This answers: What starts a fire?

In practice, this is your prevention checklist:

Remove fuel = good housekeeping, proper storage of flammables

Remove heat = hot work permit, control ignition sources

Remove oxygen = not usually possible in open air, but you can in confined processes

2. FIRE TETRAHEDRON - Adds the chemical reaction

For a long time the triangle was enough. But scientists realized flaming fire needs a 4th element to keep itself going.

4. Chemical chain reaction: Once fuel, heat and oxygen react, they create heat and free radicals. That heat makes more fuel release vapors, which react with more oxygen, which creates more heat. It's a self-sustaining loop.

This answers: How a fire sustains itself.

That's why just cooling a flaming liquid sometimes isn't enough - you have to break the chain. That's what dry chemical powder extinguishers do. They don't just cool or smother, they interrupt the radicals in the flame.

The rule changes here: All four must be present for the fire to sustain itself.

3. FIRE PENTAGON - Includes the self-sustaining factors

This is the most complete model for HSE. It takes the tetrahedron and adds human intervention.

5. Inhibition: the factor that can stop or interrupt the fire. This is your fire control.

It can be:

A fire extinguisher

A fire blanket

Cooling with water

A fire suppression system

This answers: How to stop a fire.

The pentagon shows that in addition to the four elements that create and sustain fire, there is a 5th way to deliberately break the chain.

At a glance - from the bottom table

| Model | Elements | Key addition | Main focus |

| Fire Triangle | 3 | - | What starts a fire 

| Fire Tetrahedron | 4 | Chemical chain reaction | How a fire sustains 

| Fire Pentagon | 5 | Inhibition (fire control) | How to stop a fire 

And the yellow bar sums it up perfectly:

The fire triangle is the foundation. The tetrahedron adds the reaction. The pentagon completes the picture with how to stop it.

Understand the fire. Prevent the fire.

For your HSE work, think of it like this:

Triangle for risk assessment: Is fuel, heat and oxygen together? If yes, you have a fire risk.

Tetrahedron for fire growth: Once it starts, will it generate enough heat to keep its own chain reaction going?

Pentagon for emergency response: What inhibition have you provided - right extinguisher type, training, blanket, suppression - to break the chain? 🌡️🗼🚨🏗️📝🚧🚥⚠️🚦🦺