What is a Flashover?

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  • Written By: Darrell Laurant
  • Edited By: Bronwyn Harris
  • Last Modified Date: 19 May 2020
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A flashover is something all firefighters dread, but know they must plan for. Basically, flashover is a cataclysmic escalation of a fire in a contained space, caused when heat radiating down from the ceiling ignites not only the combustible material below, but the airborne gasses released by that material. When that occurs, the entire area fills with flame from ceiling to floor, with temperatures reaching up to 1,000 degrees Celsius (1832 degrees Fahrenheit). The best-case scenario for firefighters escaping a flashover is somewhere around 17 seconds.

A tragic example of this phenomenon occurred on 18 June 2007, when firefighters in Charleston, SC were battling a rapidly spreading fire at the Super Sofa Store, a furniture warehouse. Although it is still unclear exactly what occurred, gasses released by hundreds of plastic sofas apparently flashed over, and nine firemen either burned to death or were crushed by the charred ceiling when it collapsed.

There could have been no more dangerous setting for flashover than such a factory. The chemical composition of most plastics causes them to break down at high temperatures, releasing gasses. The modern use of plastic in almost every area of home furnishings and decoration -- furniture, carpet, bedding, paints -- has exponentially increased the potential of flashover. The point at which volatile gasses begin to be released from plastic material is called "pyrolysis," and flashover often occurs within minutes.

Two other factors govern flashover. It becomes more likely if an additional oxygen source -- such as an opened door -- is presented. Also, it only occurs within a contained space with a ceiling and walls, because the gasses are not allowed to dissipate.

Ironically, improvement in firefighting equipment has left firefighters more vulnerable to flashover because it has allowed them to penetrate farther into a working fire. Beginning with some ground-breaking studies by scientists in Hong Kong, a serious effort is underway to come up with synthetic materials less likely to contribute to flashover conditions.

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