The wildland fire triangle consists of fuel, oxygen, and:

The wildland fire triangle is a fundamental concept in understanding fire behavior and fire prevention. It includes three essential elements: fuel, oxygen, and heat.

Heat is crucial because it is the energy source that initiates combustion. Without sufficient heat, the ignition of fuel cannot occur, even if there is an adequate supply of oxygen and combustible materials. In wildland fires, heat can come from various sources, including natural phenomena such as lightning or human activities like campfires. Once the heat reaches the ignition temperature of the fuel, a fire can start, which is the beginning of the combustion process.

In contrast, the other choices such as wind, the sun, and lightning, while they can influence fire activity, are not considered primary components of the fire triangle. Wind can exacerbate fire spread, the sun can aid in drying fuels making them more ignitable, and lightning is a natural ignition source, but none of these are necessary elements for fire to exist. The presence of heat, combined with fuel and oxygen, is what truly allows a fire to ignite and sustain itself.