A tetrahedron can be described as a pyramid which is a solid having four plane faces. When we talk about the fire tetrahedron, it is symbolically used to express all four essential elements that must be present for fire to occur – fuel, heat, oxygen, and a chemical chain reaction. Removal of any one of these essential elements will result in the fire being extinguished.
The fire tetrahedron is an update of the fire triangle which represented 3 element. Based on research, it has been deduced that for fire to occur, four (4) essential elements has to be present and this is what is expressed in the fire tetrahedron.
Essential Elements of the Fire Tetrahedron
A heat source is necessary for ignition to occur and different materials have different ‘flash points’ or the lowest temperatures at which they can ignite.
Combustion reactions, however, also produce heat as they burn, which further increases the fuels’ temperature. The heat may be cooled by applying water, but this is only possible for some types of fire.
Fire cannot start if there isn’t any material available to burn. Businesses and homes alike are full of flammable materials including fabrics, wood, oil, and paper. Any of these materials can serve as fuel for a fire.
Some of the materials burn more easily compared to others. Fuel is probably the hardest ‘side’ of the fire triangle you can remove, so it is advisable to ensure that they are appropriately stored so that they don’t become a fire hazard.
Oxygen is needed to sustain the combustion reaction since it reacts with the burning fuel to release carbon dioxide and heat. The atmosphere of the earth consists of 21 per cent oxygen, which means that there’s enough to trigger a fire as long as the other two components are present.
Some fire extinguishers and fire blankets remove the oxygen ‘side’ of the triangle by displacing or removing it thus causing suffocation and ceasing the combustion reaction.
Chemical Chain Reaction
The addition of the chemical chain reaction is what converts the fire triangle to fire tetrahedron.
What does chemical chain reaction imply?
A chemical chain reaction is a series of chemical reactions where the products of the reaction contribute to the reactants of another reaction. This transformation of products to reactants allows a reaction to continue with minimal or no outside influence. These chain reactions are generally triggered by a single initial reaction where an unstable product from the first reaction becomes the reactant. This process occurs until the system reaches some stable state. This stable state often comes running out of fuel because the different chemicals are in their lowest energy state (like hydrocarbons becoming water and CO2).
There are three “phases” to a chemical chain reaction: first being the initiation or the initial spark, the next being the propagation, and the final state being the termination where the system reaches a stable state.
A burning candle or other fire is an example of a chemical chain reaction. When a flammable material is surrounded by enough oxygen and is exposed to a source of heat or temperature above the flash point, a fire starts. If there is sufficient oxygen, fuel and heat, it will continue to burn until there is no longer enough of one of these three components to maintain the chemical chain reaction of the fire.