In addition to heat, fuel, and oxygen, what is required for a fire to occur?

The occurrence of fire is commonly described by the fire triangle, which consists of heat, fuel, and oxygen. In addition to these three elements, a chain reaction is necessary for a fire to sustain itself. This chain reaction refers to the ongoing process that perpetuates combustion once it has started.

When a fire ignites, the heat generated from the burning fuel creates more heat that contributes to further combustion. The initial combustion process releases gases and energy that can ignite additional fuel if the conditions are right. Without this chain reaction, once the initial heat source is removed or the fuel is consumed, the fire would extinguish.

While other factors like an ignition source, ventilation, and pressure play important roles in the fire environment, they are not part of the fundamental elements that are required for a fire to start and continue burning. The presence of a chain reaction is what allows the fire to grow and persist after it has been initiated.