What does "thermal layering" in firefighting describe?

Thermal layering refers to the arrangement of different gas temperatures within a fire environment, typically showing that hotter gases rise while cooler ones settle at lower levels. In a structure fire, the heat caused by the flames creates a gradient of temperatures: the highest temperatures are found near the ceiling where the hot gases collect, and the cooler, denser air is closer to the ground. Understanding thermal layering is crucial for firefighters as it helps them anticipate fire behavior, locate hot spots, and develop strategies for safe entry and effective suppression of the fire. Recognizing the presence of this phenomenon allows firefighters to assess the risks associated with navigating through smoke-filled environments and can influence decisions on both tactics and safety measures.