What elements must mix for combustion to occur, as illustrated by the combustion triangle?

For combustion to occur, the essential elements illustrated by the combustion triangle are fuel, oxygen, and heat. Each of these components plays a critical role in the combustion process.

Fuel provides the substance that will burn, while oxygen acts as the oxidizing agent necessary for the combustion reaction to take place. Heat is the energy that initiates the reaction by elevating the temperature of the fuel to its ignition point. This triangle concept illustrates that if any one of these three elements is removed, combustion cannot be sustained.

In this context, while some other combinations mention factors related to combustion, such as hydrogen, nitrogen, carbon, or pressure, they do not encapsulate the fundamental requirements necessary for combustion in the strict sense. For instance, the combination of fuel, air, and pressure may relate to certain conditions in specific combustion scenarios but does not universally apply to all situations involving combustion. Hence, the correct answer emphasizes the essential triplet of fuel, oxygen, and heat, which is central to understanding how combustion occurs.