What is meant by the term "thermal layering" in firefighting?

Thermal layering refers to the phenomenon of varying gas temperatures within a fire environment. In a fire scenario, heat will cause the fire gases to rise, creating distinct layers of different temperatures. Generally, the hottest layer of gases will be at the ceiling level, while cooler gases will be found lower to the ground. This stratification can significantly influence fire behavior and the conditions encountered by firefighters. Understanding thermal layering is crucial for safe firefighting operations, as it helps to inform tactics such as ventilation strategies and the timing of entry into the structure. This knowledge allows firefighters to anticipate potential hazards, such as sudden changes in conditions that could result in backdrafts or flashovers.