Which of the following is NOT one of the four elements of fire?

The correct choice is steam, as it is not one of the four fundamental elements of fire. The four essential elements that make up the fire tetrahedron are heat, oxygen, fuel, and a chemical chain reaction.

Heat is necessary to raise the material to its ignition temperature, oxygen supports the combustion process, and fuel is any combustible material that burns. Steam, on the other hand, is simply water in vapor form and does not play a role in sustaining combustion. In fact, steam can actually be used as a fire suppression method due to its ability to cool and reduce the oxygen available for a fire to continue burning. Understanding these concepts is crucial for effective fire safety and prevention, particularly in situations where managing fire risks is vital.