Which of the following is NOT a part of the combustion triangle?

The combustion triangle is a fundamental concept in fire science that identifies the three essential components required for combustion to occur: fuel, heat, and oxygen. Each of these elements plays a critical role in sustaining a fire.

Fuel is the material that burns, providing the necessary energy. Heat serves to elevate the temperature of the fuel to its ignition point, enabling combustion to occur. Oxygen is essential as it supports the chemical reaction that sustains the fire.

Pressure, however, is not part of the combustion triangle. While pressure can influence combustion efficiency and fire behavior in certain situations, it is not a fundamental requirement for the process of combustion itself. Understanding the importance of the combustion triangle can greatly assist HVAC technicians in ensuring safe and efficient operation of heating systems that rely on combustion for heat generation.