Learning to recognize when flashover conditions exist can save a firefighter’s life. What is flashover? Flashover is a thermally-driven event during which every combustible surface exposed to thermal radiation in a compartment or enclosed space rapidly and simultaneously ignites.
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Flashover normally occurs when the upper portion of the compartment reaches a temperature of approximately 1,100 °F for ordinary combustibles. Building features like concealed spaces, lower ceiling heights, room partitions, and energy-efficient or hurricane windows are more likely to contribute to flashover conditions.
Factors that influence a flashover event
- Location of fire.
- Size, volume and shape of compartment.
- Fire growth rate.
- Contents and their exposed surfaces.
- Compartment ventilation characteristics.
Factors that influence responder exposure
- Arriving on the scene at a pre-flashover state.
- Compartments are built tighter with fewer sources of air leakage.
- Bunker gear provides a false sense of security.
- Rooms filled with many more synthetics that flash at lower temperatures.
Signs of an impending flashover
- Ambient temperatures quickly double and triple as hoselines are advanced.
- Large volumes of heavy dark smoke.
- Rollover: active flame circulation in the thermal layer.
- Free burning fire in a ventilation-deficient environment.
The USFA report also linked off to the NIOSH report on a fire that killed Homewood (IL) Firefighter Brian Carey in 2010. You can find Joe Pronesti’s videos and podcast interview with Homewood Deputy Chief Steve Dejong here.