In the fire tetrahedron, what is considered the reducing agent?

In the fire tetrahedron, the reducing agent is identified as fuel. This is because fuel refers to any material that can combust, providing the substance necessary for a fire to occur. It serves as the reducing agent in the sense that during combustion, the fuel donates electrons to the oxygen, facilitating the chemical reaction necessary for fire.

While oxygen is essential for combustion and heat provides the energy required for igniting the fire, they do not act as the reducing agent. The chemical reaction describes the process through which fire occurs but is not classified as an agent in the same way that fuel is. Hence, fuel is the key component that, in conjunction with oxygen and heat, completes the tetrahedron, ultimately sustaining the fire.