What describes the tendency of gases to separate into layers according to temperature?

• A. Rollover
• B. Decay
• C. Thermal Layering
• D. Fully Developed Stage

Answer: (C)

Thermal layering describes how gases separate into layers based on temperature. Warmer air is less dense and rises, while cooler air is denser and sinks, creating distinct layers with different temperatures and densities. This stratification persists unless mixing from convection, ventilation, or turbulence disrupts it, and it has practical importance in fire safety because hot gases tend to accumulate near the ceiling while cooler air remains lower, affecting ventilation and suppression planning. Other terms refer to different fire behavior stages and don’t capture this temperature-driven density separation.