Rochefort roof blast
25 Feb 2018

Smoke build up in hidden spaces = deadly surprises

Bjorn Ulfsson & Terri Casella
MSB - The Swedish Civil Contingencies Agency

The video report above is short segment from a larger video report within MSB's 90 Sekunder Educational Video Series.

By Bjorn Ulfsson & Terri Casella

Smoke buildup in hidden spaces is one of the most dangerous situations in structural fire fighting. A large attic or a warehouse attached to other buildings are prime examples of when a fire gas explosion can take a firefighter's life without even a moment's notice.

The sudden rush of fresh air can re-awaken a smouldering fire and create a backdraft, or like in this tragic case from Belgian Rochefort: it can serve as a pre-ignition for a large volume of cold fire gases, causing an attic to explode.

The violence of a fire gas explosion can be compared to that of a gasoline vapor explosion; the same force, the same rapid development.

Tactical ventilation from a save distance, fire gas cooling from the outside, and - most importantly - pre study and pre-planning in order to expand upon your own knowledge of fire gas behavior in complex structures - is key to preventing these kinds of deadly, sudden surprises.

No nozzle or any amount of water can stop the development, once ignition has started in a premixed volume of smoke.

Rochefort lifting roof tileWhen oxygen and carbon levels are already at "optimum mixture", and the carbon energy versus oxygen is "perfect", the flick of a light switch can sometimes be enough to start a reaction in the smoke layer. Often, when these situations happen, the initial fire has burned out, and the building may therefore "seem" safe to enter. Sometimes, there is not even any signs of heat.

The death of volunteer firefighter Eric Pero (see the video above) is one of a series of tragic events in the mid 2000's, which caused Belgium to step up their fire training and put substantial money into a national Fire Behavior training for all firefighters.


Belgium backdraft