Fatal fireplace, what’s the flashover impact | EUROtoday

Listen to the audio model of the article

At the origin of the Crans-Montana tragedy there’s a phenomenon that marks the transition from a controllable fireplace to an out-of-control one: the so-called flashoverearlier than which even firefighters usually must retreat. Despite the devastation, fires of this sort nonetheless go away treasured clues for reconstructing what occurred, even when the technical-scientific analyzes can take weeks or months, explains Valeria Di Sarli, of the Institute of Sciences and Technologies for Sustainable Energy and Mobility of the National Research Council (Cnr-Stems).

Non-random explosion

A flashover “is not an explosion, even if the visual effect may be similar, and above all it is not generated by chance”, observes the professional. This phenomenon, also referred to as ‘generalized fireplace’, represents the purpose of arrival of a exact mixture of things, on which thermal vitality and the presence of flamable gases in a closed surroundings rely, with consequent heating of all supplies. “The time it takes to develop also depends on environmental conditions,” he provides. During a flashover, “the fire can start in a limited way, involving for example a single object such as furniture or a curtain, while hot fumes containing combustible gases, derived both from the combustion itself and from the pyrolysis of the materials heated by the fire, rise towards the ceiling, forming a layer that progressively thickens and reduces visibility

The role of oxygen

The heat radiated from the fume layer and from the surfaces already involved causes the surrounding materials to heat up. When the temperature of the fumes and surfaces reaches around 500-600 °C, the gases and materials self-ignite and numerous objects, even far from the initial fire, catch fire almost simultaneously”. In these circumstances, the opening of doorways and home windows favors the entry of oxygen, which in an already crucial part additional fuels the fireplace. Now the lengthy work of investigations begins, seeking clues that enable us to know why such a violent fireplace developed.

“First of all, the initial fire must be identified, identifying obvious traces such as deep or directional burns on the surfaces. The path of the fire is then analysed.” In reconstruction, “all elements are closely related to each other”. This is an built-in evaluation, by which “it is essential to also consider the type and arrangement of combustible materials, such as fabrics and synthetic materials, and evaluate any sources of ignition”. In the case of the Crans-Montana venue, the primary suspicions targeted on the pyrotechnic fountains and false ceilings, usually manufactured from flammable supplies.