Fire Tetrahedron

What Does Fire Tetrahedron Mean?

The fire tetrahedron is a visual representation of the four properties that must be present for a fire to occur, with each property depicted as a different side of a pyramid. You’ll find this symbol on a safety sign.

The four elements of the fire tetrahedron are:

• Fuel
• Heat
• Oxygen (or another oxidizing agent)
• A chemical chain reaction

The fire tetrahedron is meant to provide a simple explanation of how fire works, which conditions increase the risk of fire, and how to extinguish it.

Safeopedia Explains Fire Tetrahedron

The fire tetrahedron is an update on the fire triangle, which contained only three elements (fuel, heat, and oxygen). The fourth element (chemical reaction) was added to communicate the fact that a fire must produce a continuous exothermic (heat-generating) chemical reaction in order to ignite more fuel and sustain itself.

The Four Elements of the Fire Tetrahedron

• Fuel: any element that is capable of combustion
• Heat: causes the fuel to release the vapors that will be ignited
• Oxidizing agent: the component that the fuel vapors react with and combust
• Chemical chain reaction: an exothermic chemical reaction caused by the combustion, which perpetuates the fire by creating more heat, releasing more fuel vapor, and combusting in reaction with the oxidizer

Source: Handbook of Fire and the Environment

Using the Fire Tetrahedron to Extinguish Fires

Each element of the fire tetrahedron points to a method of extinguishing a fire.

For instance, properly storing fuel can reduce the likelihood that it will be in an environment where all three other elements of the tetrahedron are present. Likewise, a natural gas fire can be extinguished by turning off the supply of gas that is feeding it.

Water can suppress a fire by reducing the temperature to the point where it is not sufficiently hot to keep the fire going. It can also wash away or dilute the fuel that the fire is using as a combustible material.

Fire’s need for an oxidizing agent means that it can be smothered with dirt or a fire blanket. Reducing the concentration of oxygen in an atmosphere also reduces the risk of a fire igniting.

In workplaces that have sensitive electrical equipment, fires may need to be extinguished in a manner that does not damage the equipment. In this instance, a halon-gas extinguishing system can be used to disrupt the chemical reaction necessary to sustain the fire.