Flashover. This term – which in Greek is descriptively rendered as “generalized ignition” – explains the circumstances that caused the deadly tragedy at the Constellation bar in the Swiss resort on New Year’s Eve, in which 116 were injured, shocking world opinion.
The Swiss authorities, who in a recent press conference about the painful incident, said that the fire that broke out in the bar took on the characteristics of flashover, after they came into contact with the fine ceiling, igniting a fire that spread with great speed.
But what is flashover? According to the US National Fire Protection Association (NFPA), generalized ignition, known internationally by the English term flashover, is the almost simultaneous ignition of most directly exposed combustible materials in a closed space.
When a fire breaks out in a space, it will grow and spread, consuming any combustible material in its path. But as the flames grow, hot gases are trapped by the roof and forced downwards onto unburnt combustible material.
Warning signs
According to the NFPA, there are three telltale signs that a flashover is imminent: the presence of thick, black smoke moving in circles, smoke being pushed out of a door or window opening, and smoke that has accumulated as low as a doorknob. The practical sign is that thin objects on the floor (such as a sheet of paper) begin to ignite, and soon any combustible material or object begins to burn.
There are two characteristics that give this kind of dangerousness to the phenomenon. Firstly, the very short time evolution of this particular type of fire, between 2 and 10 seconds, which initially creates little room for reaction. Secondly, the extremely high temperature, which adding up the individual heat loads can reach 1,000 degrees Celsius.
Fire safety experts have identified several factors that , including the height of the ceiling and the presence of combustible materials in the ceiling and walls, such as for sound insulation. If the ceiling height is lower, there is less space for the hot gases to accumulate and less time is required for them to heat up all the other combustible materials in the room.
“Even fully equipped firefighters find it difficult to escape alive from such situations,” says the head of the Department of Fire Protection Engineering at the Worcester Polytechnic Institute, Milos Puchovski, speaking to the Washington Post.
Could it be avoided?
The question however remains, could the multi-death tragedy have been avoided? “The use of highly flammable materials in the roof and walls, usually for soundproofing reasons, but also having a very low ceiling are aggravating factors,” Lund University Fire Safety Professor Brian Mitcham tells WP. He suggests the obvious, the adoption of less flammable materials for all interior parts, especially the roof.
Experts prefer the use of an automatic fire extinguishing system with water, through heads activated by heat (fire sprinkler), which has the ability to act at an initial stage, when the released temperatures are still low and the fire can be brought under control. “Heads are part of any sound fire suppression system,” says Christian Dubeau, NFPA vice president.
NFPA press officer Lorraine Carley notes in a recent post that “safety doesn’t happen by accident,” urging those in confined spaces to check where the exits are. “Leave at the first sign of trouble,” he notes, among other things. And he adds that the general construction provision, with the existence of many escape exits and the right building materials, compose an ecosystem that usually repels fire.
