Fire Triangle Vs Fire Tetrahedron

Recent studies in fire safety field has revealed that there is a fourth component necessary for fire. This is the chain reaction. This therefore changes the traditional three components that composed the fire triangle which included:

• Heat
• Fuel
• Oxidizing agent which is usually oxygen.

This was usually represented in a diagram as follows:

 This was transformed to include the fourth component, chemical reaction.

The fire tetrahedron represents the addition of a component, the chemical chain reaction, to the three already present in the fire triangle. Once a fire has started, the resulting exothermic chain reaction sustains the fire and allows it to continue until or unless at least one of the elements of the fire is blocked. Foam can be used to deny the fire the oxygen it needs. Water can be used to lower the temperature of the fuel below the ignition point or to remove or disperse the fuel. Halon can be used to remove free radicals and create a barrier of inert gas in a direct attack on the chemical reaction responsible for the fire.

Combustion is the chemical reaction that feeds a fire more heat and allows it to continue. When the fire involves burning metals like lithium, magnesium, titanium, etc. (known as a class-D fire), it becomes even more important to consider the energy release. The metals react faster with water than with oxygen and thereby more energy is released. Putting water on such a fire results in the fire getting hotter or even exploding. Carbon dioxide extinguishers are ineffective against certain metals such as titanium.

Therefore, inert agents (e.g. dry sand) must be used to break the chain reaction of metallic combustion.In the same way, as soon as one of the four elements of the tetrahedron is removed, combustion stops.

Further research over the years revealed a fourth necessary component of fire, the chemical chain reaction. The Fire Triangle was consequently transformed to the Fire Tetrahedron. Put it simply, a Tetrahedron is a solid pyramid with four plane faces (from the Greek words ”tesseris edres”), each one representative of the four necessary elements.

The blogger is a research student at the university of Nairobi