What does the term "thermal layering" refer to in firefighting?

The term "thermal layering" refers to the phenomenon where heat accumulates at the ceiling level in a confined space, particularly during a fire. This occurs because warm air, which is less dense than cooler air, rises and creates a thermal gradient within the structure. As a result, the temperature at the ceiling can be significantly higher than at lower levels, often leading to hazardous conditions for occupants and firefighters.

Understanding thermal layering is crucial for firefighters, as it influences the fire's behavior and informs tactics for ventilation and firefighting operations. For instance, if firefighters are aware that there is a buildup of heat and potentially combustible gases near the ceiling, they can take measured approaches to attack the fire or ventilate the space safely, reducing their risk of encountering a flashover or other dangerous situations.