09-21-2006, 05:39 PM #1
- Join Date
- Mar 2005
Backdraft: Taxpayer Ventilation Problems
If you are fearing that a backdraft is imminent in a store, the obvious method of relieving the hot smoke and gases is to ventilate at the highest point. Now what if that highest point is either unaccessible for whatever reason, too dangerous, or nearly impossible to get a vent hole through the many layers of roofing some stores may have?
Is it safe to assume that some sort of Horizontal ventilation would take place. Rear doors? Taking the glass in the store front?
09-21-2006, 06:40 PM #2
Firstly, whilst venting at the highest point is often seen as a method of preventing 'backdraft', this strategy also carries the potential to make a fire worse. Having said that, in an unoccupied structure the approach is viable and the risk is generally calculated.
Where backdraft indicators are present the application of a horizontal venting action is more likely to result in rapid fire progress.
My chosen tactic in this scenario would be to create small openings in which to apply streams of water from the exterior, using a fog pattern in a burst & pause fashion, in an effort to create a atmosphere that is too humid to support the fire's progress.
09-21-2006, 08:32 PM #3
- Join Date
- Sep 2004
- Quebec, Canada
Why do I smell a fog, solid, 3D debate coming-up???
Who let the dogs out!!!!
09-21-2006, 09:20 PM #4
I don't give a rat's *** if the fire "gets worse" what I do care about are the brothers in front of the storefront and moving in when some j/o takes the glass. Get the roof, natural vent points, skylights (draftstop too), scuttle, mushroom fans, if it can come off take it off, cut if you can but get the roof.
Vent and Put water on the seat of the fire. As for the fog and exterior, do what works with your department, just don't do it around me.
09-21-2006, 10:15 PM #5
Controlling the Fire Environment
If backdraft conditions exist within an occupancy, there are unlikely to be savable victims (within that set of compartments). However, this may not be the case in the exposures or other compartments in the building that are isolated from the fire area.
The priority in this case is the safety of the firefighters involved and potentially savable occupants outside the area in which the backdraft conditions exist. Worsening fire conditions and damage to the structure due to the overpressure created by a backdraft present a significant threat to both firefighters and occupants of immediate exposures.
The first key decision in this process is selection of strategic mode based on your department's risk management strategy. If you are going to operate in an offensive mode, control of the fire envronment is critical both to our safey and success. If there are no savable lives or property, the point is moot.
Operating in an offensive mode, two options exist to mitigate the hazards presented by backdraft conditions. One is ventilation at a high point which will release the hot flammable products of combustion, allowing them to burn outside the building rather than deflagrating inside. As Paul observes, another is to reduce the temperature of these gases and increast the thermal ballast by introducing water (commonly in the form of fog) into the compartment. It is important to consider that backdraft conditions need not involve the entire occupancy, but may be encountered within a single compartment or even a void space.
Effective use of both tactical ventilation and gas cooling should be considered when faced with this type of situation.Ed Hartin, MS, EFO, MIFireE
09-21-2006, 11:59 PM #6
Agaudio, GREAT QUESTION!
I have never tried this nor do I want to, but Chief Dunn or Chief Norman, discuss this in one of their seminar classes.
Their scenario is much of the same as your question. It could be a 2 story taxpayer or a row of stores with apartments above.
If the store is presenting with a Backdraft condition, recognizing it is your first order of business. If you do not, you are going to find out in a not-so-desirable way that can hurt or kill the brothers in the front.
Obviously, vertically ventilating the building is the best way to prevent a backdraft in the building. However, if presented with the situations that I described above with no way to vent the store vertically then pull everyone away from the front of the store.
Stretch lines to flank the fire (one in front of each exposure store) and if possible shield yourself with a car or something of substantial size BUT STAY OUT OF IN FRONT OF THE STORE! Make sure you are in front of the exposure store.
WITH A COORDINATED EFFORT
One member with a VERY LONG HOOK (10' or more) should reach from the protection of the exposure store AND BEING CAREFUL NOT TO BE IN FRONT OF THE FIRE STORE. This member should use the store that affords the most protection (i.e. if exposure 2 has a brick wall and exposure 4 is another glass storefront, you would obviously want to be in front of exposure 2 using the brick wall for protection).
AGAIN, WITH A COORDINATED EFFORT, (the lines are ready & the member with the hook is ready AND THEY KNOW WHAT EACH OTHER HAS TO DO!)
The glass can be broken in the fire occupancy AND IMMEDIATELY AS THE GLASS IS FALLING the water should be thrown into the opening in the building.
I am not saying that this will completely avert the backdraft, but two 2 1/2" hose lines flowing into a building that IN THEORY would be sucking in water with the air could cool down the atmosphere and decrease your chance of the catastrophic explosion that we know can occur from a backdraft.
Whatever you do, make sure the members are protected and realize that this is a VERY DANGEROUS situation that members could get hurt if it is not dealt with carefully.
REMEMBER, IT IS JUST A STORE! If it is presenting with signs of Backdraft, then there are NO VIABLE victims in the occupancy. Temperatures are well over 1000 degrees and the fire has used up all available oxygen. Take a SLOW DOWN approach and conduct your operations safely.
I want to re-iterate that I have never tried this technique. I think Paul's fog technique would work, but I am not sure how close you would have to be to the building to perform the required task with a burst from a fog stream. The technique that I am describing allows the Engine members to be outside of the collapse zone and affords some protection to the Ladder member with the hook.
As always, an honor to post along side of "Hartin" and "PaulGrimwood"! Class Acts! I don't think that this one will turn into a "water fog vs solid stream" debate but I guarantee that you will have a few ways to mitigate the situation from both angles!
09-22-2006, 12:24 AM #7
Originally Posted by NDeMarse
- Join Date
- Apr 2003
09-22-2006, 01:47 AM #8
Question. Exactly where do you make this "small opening"? If the entire front is glass, how do you acomplish that?
Last edited by nyckftbl; 09-22-2006 at 01:54 AM.Proud East Coast Traditionalist.
09-22-2006, 05:36 AM #9Originally Posted by nyckftbl
Yes erics99 is correct and I have seen this method used by FDNY under such circumstances, in conjunction with a roof operation where viable.
I too have used this tactical approach on many occasions with great success. It is most certainly an 'indirect' use of a fog pattern and the two points Ed Hartin makes are important - (1) (backdraft) conditions suggest an absence of viable life in the compartment; and (2) the approach of fog bursts and roof ventilation (if possible) are coordinated. I would suggest the fog pattern comes first.
NDeMarse is clear about avoiding a direct frontal approach and using all forms of natural protection and I couldn't agree more. Approaching from the adjacent fronts will provide some protection and the method is demonstrated on p137 of my 1992 TACTICS BOOK
Making small holes in a glass front near the corners for application of twin fog lines may or may not be practical. Sometimes the door is at the side .... we take that. Sometimes there are quarter panels we take them. If not take the main glass itself but go for a low corner. If the front is security grilled you have a problem. At least if the shop front blows you will gain some protection from the side.
Again, p22 of 3D Firefighting demonstrates that this approach does not always work and you must be clear of the shop front at all times.
Where backdraft indicators are clearly evident (or even if they are not suspect them in a sealed shop front) a coordinated approach from the sides and roof seem to work well in protecting firefighters. I would say the horizontal entry and fog bursts come first but that is only my personal view.
Last edited by PaulGRIMWOOD; 09-22-2006 at 05:41 AM.
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