Which of the following is NOT one of the three necessary elements for fire?

The correct answer is sustained pressure, as it is not one of the three necessary elements for fire. The three essential components required for fire to ignite and continue burning are heat, fuel, and oxygen, commonly referred to as the fire triangle.

Heat is necessary to increase the temperature of the fuel to its ignition point. Fuel provides the material that will burn, while oxygen is required to sustain combustion. Without any one of these elements, a fire cannot exist.

Sustained pressure, while it may affect how a fire burns—such as influencing the spread of flames or the intensity of a fire—is not a fundamental element required for the initiation and maintenance of combustion.