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Flashover is a dangerous escalation of fire in a confined space caused by heat igniting combustible materials and gases. It can occur within minutes and temperatures can reach 1,000 degrees Celsius. Plastic furniture stores are particularly dangerous due to the release of gases during pyrolysis. Flashover is more likely with additional oxygen and only occurs in confined spaces. Improved firefighting equipment has made firefighters more vulnerable to flashovers. Efforts are being made to find synthetic materials that are less likely to contribute to flashover conditions.
A flashover is something all firefighters fear, but know to plan for. Basically, flashover is a catastrophic escalation of a fire in a contained space, caused when heat radiating from the ceiling ignites not only the underlying combustible material, but also the gases in the air released by that material. When that happens, the entire area is filled with flames from ceiling to floor, with temperatures reaching 1,000 degrees Celsius (1832 degrees Fahrenheit). The best-case scenario for firefighters escaping a flashover is about 17 seconds.
A tragic example of this phenomenon occurred on June 18, 2007, when firefighters in Charleston, SC were battling a rapidly spreading fire at the Super Sofa Store, a furniture warehouse. While it’s still unclear what exactly happened, gases released from hundreds of plastic sofas apparently flashed and nine firefighters burned to death or were crushed by the charred ceiling when it collapsed.
There could not have been a more dangerous environment for flashover than such a factory. The chemical composition of most plastics causes them to break down at high temperatures, releasing gases. The modern use of plastic in nearly every area of home furnishing and decoration – furniture, carpets, bedding, paint – has exponentially increased the potential for flashovers. The point at which volatile gases begin to be released from the plastic material is called “pyrolysis” and flashover often occurs within minutes.
Two other factors govern flashover. It becomes more likely if an additional source of oxygen is presented, such as an open door. Also, it only occurs within a confined space with ceiling and walls, because the gases cannot dissipate.
Ironically, improved firefighting equipment has made firefighters more vulnerable to flashovers because it has allowed them to penetrate deeper into a functioning fire. Starting with some pioneering studies by Hong Kong scientists, a serious effort is underway to find synthetic materials that are less likely to contribute to flashover conditions.
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