What is the name of the model that includes Heat, Fuel, Oxygen, and Chemical Chain Reaction?

• A. Fire Triangle
• B. Fire Tetrahedron
• C. Fire Circle
• D. Fire Pyramid

Answer: (B)

Combustion needs four interacting elements to occur: heat to provide the activation energy, fuel to feed the reaction, oxygen to react with the fuel, and a chemical chain reaction that keeps the flame going through radical reactions. The traditional three-element model was the Fire Triangle, but a fourth element—the chemical chain reaction—was added because the ongoing flame depends on these radical chain reactions. When any one element is removed, the flame is extinguished. This four-element model is called the Fire Tetrahedron, which is why it’s the correct term. The other names aren’t standard models for describing how flames are sustained.