Upward spread of fire within a structure is primarily caused by which type of heat transfer?

Upward spread of fire within a structure is primarily driven by convection. This process involves the movement of heated air and gases rising due to their lower density compared to cooler air. As the fire heats the air in a room, this warm air rises, carrying heat energy with it. It can then ignite combustibles located above the initial fire source, contributing to the upward spread of flames and increasing the overall intensity of the fire within the structure.

Convection plays a critical role in how fires develop and spread in enclosed spaces. It explains why heat and smoke often accumulate near the ceiling before moving horizontally or descending as it cools. Understanding this process is vital for firefighters as it informs strategies for ventilation and fire suppression, aiming to control or redirect the movement of heat and fire.