USFA: Recognizing Flashover

Firefighters stoking flames in the flashover can
Photo from FDIC International by Tim Olk
Firefighters stoking flames in the flashover can
Photo from FDIC International by Tim Olk

The U.S. Fire Administration (USFA) recently released a brief article dealing with the fire behavior phenomenon known as flashover.

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.



Firefighter Training Bulletin: Flashover

Firefighter Safety: Understanding and Avoiding a Flashover


Differentiating the “Fireground Phenomena”

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.

Wright McMeekan/YouTube

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.

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