Kitchen Table Debriefs - Hostile Fire Events (Part II)
Edward M. Raposo
In fiction and movies, recognition is simple: wisps of smoke appear from below a door in an otherwise smoke-free environment, only to be completely drawn back into the fire room again. In reality, most times the environment is chaotic, with smoke charging out of every possible crack and crevice. This is because, in reality, there are multiple processes going on at the same time. Fire in one room may be going through the decay phase, but fire is another room may be in the free burning phase. Art doesn’t always imitate life.
I am amazed to read online forums or discussions on YouTube videos where firefighters will literally argue that a particular explosion isn’t a backdraft simply because it did not display the same characteristics (puffing smoke is a common one) of a backdraft from the movie.
A backdraft occurs when an oxygen-starved smoldering fire, in either the growth or decay phase of combustion, receives enough of a blast of oxygen to rekindle and reignite, pure and simple. Unfortunately, there are no indicators to predict a backdraft will occur, but there are conditions and signs usually observed whenever backdrafts occur, and we need to watch for these as a warning. The way to recognize a potential backdraft scenario is as follows:
•Thick smoke, under pressure, puffing or pushing out from small openings •Smoke flowing back into a burning room just after a firefighter advance, forcible entry, of ventilation operation •Dense black or dark brown smoke indicating a large quantity of CO gas in the smoke (Smoke could also be mustard-colored) •Window glass discolored from heat and smoke indicating a long decay-stage fire.
These conditions do not guarantee a backdraft will occur, but these indicators are usually present when a backdraft DOES occur.
What You Can Do
Your protection against a backdraft, other than your turnout gear (which may help reduce any injury from the blast), is preventing it from happening in the first place.
The steps you can take to attempt to prevent a backdraft from occurring include vertical ventilation and application of copious amounts of water. Unfortunately, both of these activities also introduce oxygen to the target room.
Vertical ventilation, even if it triggers an explosion, will vent everything up and out of the structure. This is usually the safest place to release this energy.
The application of water on the fire is your other option. Water is the tool of choice when fighting fires because of its heat-absorbing qualities, low cost and high availability. Water does not suffocate a fire, but it quenches the object that is burning, absorbing the heat and thus, putting the fire out (removing the heat and interrupting the fire tetrahedron).
Water application, however, may also trigger the backdraft explosion. Therefore, water must be applied using good practices, in other words, indirectly applied from outside the fire room (preferably from outside the building and through a breached window) crews should be safely positioned and angled to the side of the window or doorway. Chief Dunn, among others, refers to this as flanking the fire.
No matter where you get your information from, and no matter what you use as your source of training, the bottom line is: wear your protective clothing all the time on the fire ground, perform vertical ventilation, cool the environment, and keep out of it’s way!