This is the first bulletin in a two-part series on flashover and backdraft. In Part 1: Flashover, you will learn why situational awareness is critical for recognizing when potential flashover conditions exist.
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. 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.
Uncoordinated ventilation caused flashover killing Illinois firefighter
Investigators say crews failed to recognize signs of an imminent flashover; firefighters were between the fire and ventilation points.
Read about this fatal flashover
and safety recommendations for fire departments to follow.
Take defensive steps to provide you with valuable time to escape the area.
Steps to protect yourself
- Always plan an evacuation route.
- Cool the area as soon as possible: fog pattern into the upper thermal layer.
- Switch to straight stream to cool contents and create a buffer zone.
- If conditions worsen despite your attempts to cool the room, get out and reassess the situation.
Michael Salzano, battalion chief, Fort Lauderdale Fire Department, offers these additional notes:
- Not all fires progress to flashover, but every fire has flashover potential.
- Have an exit strategy. If you are inside the building 10 feet or 100 feet, have a plan and consistently communicate that plan to each other.
- Situational awareness is essential; don’t get tunnel vision and miss the signs of flashover.
- Communication between interior crews and command is most important. Notify command of any changes in fire, smoke or heat behavior.
More information about recognizing flashover
Understanding and Avoiding a Flashover. Salzano, M. (2014). Fire Engineering.
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