What aspect of a fire does the term 'thermal layering' relate to?

The term 'thermal layering' refers specifically to the temperature stratification of gases in a fire environment. As a fire burns, it generates hot gases that rise due to their lower density compared to cooler air, leading to the formation of distinct layers of temperature within a space. This layering creates a situation where hotter gases accumulate near the ceiling while cooler air remains closer to the floor. Understanding thermal layering is essential for firefighters as it influences smoke movement, visibility, and the potential for re-ignition, as well as the hazard of flashover. This knowledge helps firefighters make informed decisions about ventilation and attack strategies during firefighting operations.