10/11/2026
What is Thermal Rebound? Check out a highlight of our Thermal Rebound Drill!
Thermal Rebound refers to the phenomenon where a fire, which was initially knocked down or suppressed, seemingly "re-ignites" or intensifies after a short period. This can happen even after firefighters believe they have successfully controlled the fire.
How Does it Happen?
Think of it this way:
• Initial Attack: When firefighters first attack a fire with water or other extinguishing agents, they cool down the burning materials and displace oxygen, effectively "knocking down" the flames.
• Heat Sink: However, the fire has been burning for some time, heating up the surrounding structures (walls, ceilings, floors) and contents (furniture, etc.). This heat "soaks or sinks" deep into these materials.
• Thermal Mass: These materials have "thermal mass," meaning they can store a significant amount of heat energy.
• Surface Cooling: The initial fire attack primarily cools the surface of the burning materials. The heat stored deep inside the thermal mass remains.
• Re-Heating: Once the immediate cooling effect of the water or extinguishing agent wears off, the heat stored within the thermal mass starts to "bleed back" to the surface.
• Re-Ignition: This released heat can re-ignite any remaining fuel or pyrolyze (break down) nearby combustible materials, creating new flammable gases that can then ignite, causing the fire to "rebound."
Why is it Dangerous?
• False Sense of Security: Firefighters might believe the fire is under control and relax their guard, only to be surprised by a sudden flare-up.
• Rapid Fire Spread: The re-ignited fire can spread quickly, especially if it involves accumulated flammable gases (like in a backdraft scenario, although thermal rebound is distinct from backdraft).
How Do Firefighters Combat It?
• Continued Cooling: Applying water in the absence of flames and even after the visible flames are gone helps to cool the thermal mass and prevent thermal rebound.
• Thermal Imaging Cameras: These cameras help firefighters detect hidden sources of heat that might not be visible to the naked eye. And they can gauge the overall effectiveness of fire attack efforts.
Video filmed with a FLIR K85.
Check out the full video on our YouTube channel:
https://youtu.be/qj61KEZ_WXg
