What component is NOT part of the fire tetrahedron?

The fire tetrahedron consists of four essential components that are required for combustion to occur: heat, fuel, oxygen, and a fourth component that is often referred to as a chemical chain reaction. In the context of this question, nitrogen is not considered one of the necessary components for fire; therefore, it is the correct answer.

While heat, fuel, and oxygen are all critical elements of the combustion process, nitrogen is predominantly an inert gas in the atmosphere and does not contribute to the chemical reactions that sustain fire. Understanding the components of the fire tetrahedron is crucial for fire suppression efforts, as removing any one of these elements can effectively extinguish a fire.