Which four components comprise the Fire Tetrahedron?

Which four components comprise the Fire Tetrahedron?

• A. Fuel, Oxygen, Heat, Vaporization.
• B. Fuel, Oxygen, Heat, Chemical Chain Reaction.
• C. Fuel, Oxygen, Heat, Pressure.
• D. Fuel, Oxygen, Heat, Containment.

Answer: (B)

The Fire Tetrahedron adds a fourth element to the familiar triangle of fuel, oxygen, and heat by including the chemical chain reaction that sustains flame. Even when fuel, oxygen, and heat are present, the flame continues only if the reactive chemical chain reactions in the flame zone can proceed. These chain reactions generate and propagate radicals (like H, O, OH) that keep the combustion process going. That’s why disrupting those reactions—through cooling, removing fuel, starving oxygen, or using agents that scavenge radicals—can extinguish a flame even if heat, fuel, and oxygen remain.

The other options don’t fit because vaporization, pressure, or containment aren’t the fundamental fourth requirement that keeps combustion going. Vaporization is part of how a fuel becomes available, but it’s not the separate sustaining element; pressure and containment influence flames in other ways, but they aren’t the essential fourth component of the fire itself.