Exploring the Backdraft
Show me a firefighter and I'll show you someone who doesn't associate the term backdraft with the popular movie of the same name. (1991) Backdrafts are without any shadow of a doubt one of the most dangerous events a firefighter can encounter during fire ground operations and should be treated as such. I myself have only been present at one such incident but I remember it all to well. We received a call as mutual aid backup for another local department. A two story home with heavy involvement in the first floor and no signs of spread to the second floor. We arrive and are soon followed by a third department answering the call for mutual aid as well. I quickly set our hoses in place and begin my size-up to see what our situation was. As I am doing this a member of the third fire department has set up a ladder and made his way to the second floor balcony. Right off I felt this guy was asking for trouble. He was given no authorisation to do what he was doing. Another key factor to this guys lack of training was the fact he failed to see the telltale crackling of the upper window.
Before I knew it this gentleman knocked out a window with a 3 foot pike pole and smoke rushed out as quick as lightning, followed alongside the smoke was trails of fresh fire. Glass rained down on the scene, including my chief who was not impressed with the destructive actions of this individual. Lucky for him he suffered no injuries other than a quick verbal beating from all on the scene and a request to stand down and let us do our work. What could have been a routine fire with great potential for saving the structure turned into a hopeless situation as the entire second floor became involved.
What caused the explosive re ignition of a smoldering fire? The cause was a backdraft. The 5th edition of "Essentials of Fire Fighting and Fire Department Operations" defines a backdraft as "instantaneous explosion or rapid burning of super heated gases that occurs when oxygen is introduced into an oxygen-depleted confined space. The stalled combustion resumes with explosive force.
Backdraft In Simpler Terms
In simpler terms air is introduced to material that is not finished burning because oxygen was taken away from it. Remember day 1 of our training when our trainer broke out the fire tetrahedron or for the older dogs on the porch the fire triangle. To the right is the image we all should have seen in some form or another, or at least I hope we have!
In a typical fire 4 things need to be present, fuel, oxygen, heat and a chemical chain reaction. Idealy this is the perfect fire. When one of these items are missing the fire will not burn. This is thought to be the goal of the fire department to take away one of these things to stop the fire dead. The sad thing is when the fire itself takes away from one of these things our actions may be the worst thing possible for fire suppression.
What happens when the fire runs out of oxygen?
In a confined space oxygen is not going to be as plentiful as the fire would like it to be. Thus it will run out. When this occurs the fire begins to smolder and a problem situation arises. The material in the room including unburned gases are at or are above their ignition temperature. They are simply not being supplied enough oxygen to burn.
One might assume this means the fire is out and we can continue with fire operations. This is a sad and sometimes fatal mistake.
The smoldering fire now presents a danger more advanced than it did while it was burning because now you could be dealing with a backdraft. As soon as oxygen is introduced into the fire the chain reaction will be completed and the result will be re ignition with tremendous force and power behind it. The more confined a space is the more force and intensity the backdraft will carry.
The movie Backdraft
How we are decieved
We often associate backdraft with someone opening a door or window and instantly the backdraft occurs. This is not always the case. In fact many studies have been done on cases in which the vent crew were opening up the ceiling and a crew inside were doing overhaul. Suddenly without warning the interior crew are hit with a backdraft. Why? Because the air that was let in through the ceiling took time to reach the smoldering fire and complete the chain reaction needed to re ignite the fire.
Are backdrafts dangerous? Indeed, and extremely so! Are they a constant risk? I am afraid they are. Are they avoidable? Completely.
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Know the warning signs!
There are several indicators that the potential for backdraft is present.
- Is smoke leaving the structure in puffs? If so then be warned that the introduction of air into the structure could trigger a backdraft.
- Does the smoke appear to be trying to reenter the building as if it is being drawn back in. This is called the sucking phenomenon. If you notice this than think twice about venting the structure.
- Notice the color of the smoke coming from the building. If the smoke is black becoming dense gray and yellow than you are looking at smoke coming from an oxygen starved fire. Don't open that door!
- Before you advance on the fire look at the windows. They are great indicators of what is going on inside the fire structure. Are the windows stained? Are they showing signs of cracking due to heat? If so then on the other side is a fire waiting to be fed oxygen so it can regain it's momentum. Don't feed the fire!
Knowing the warning signs means knowing when and how to react. Fighting fire is an ongoing conversation between you and the fire. You have to listen and respond accordingly. It is a vital process that you learn the indicators of backdraft and how to be prepared to handle them. A backdraft can and usually will be a major occurrence on the fire department and will put a huge damper on the operation as a whole.
More video samples.
Learn From The Past For Survival In The Future
Any time a backdraft indicator is present all fire ground staff need to be made aware. If you have spotted one of these warning signs radio your incident commander and make sure they know that a backdraft is possible and make sure the rest of your firefighters are aware as well. We have to look out for each other.
It is impossible to predict with 100% certainty how a backdraft will react. What is known is the potential for injury or death is high anytime a backdraft occurs. I hope that I have at least opened you up to the dangers of backdrafts and how to avoid them in your future work on a fire department.
Being aware and staying safe is something you can not afford to avoid or neglect. It is the job of every firefighter to operate in the safest manor possible and knowing the signs of dangerous fire behavior events is a must.
Share your backdraft stories
usat from Sarawak on October 30, 2018:
Fire when its small is a nice friend but not when it become big fire.
Sam Little (author) from Wheelwright KY on September 03, 2012:
Come on guys and gals I would love to hear some real on scene stories.