What does "thermal layering" refer to in fire behavior?

The concept of "thermal layering" refers to the stratification of heat and smoke within a fire environment, particularly in a building. When a fire occurs, heat rises due to its lower density compared to cooler air. This results in a temperature gradient within the space, with hotter air and smoke accumulating near the ceiling while cooler air remains closer to the floor. This layering can significantly influence fire behavior, smoke movement, and the conditions firefighters encounter if they enter a structure. Understanding thermal layering is crucial for effective firefighting strategies, as it helps firefighters predict how and where heat and smoke will behave in a burning building, allowing for safer and more efficient operations.

The other options do not accurately capture the essence of thermal layering in the context of fire behavior. The arrangement of firefighters at the scene pertains to tactical positioning, while spreading fire for control and training methods relate to operational practices rather than the physics of heat and smoke dynamics.