Venting - WHERE & WHEN?!

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Originally Posted by RFDACM02

It is evident that there may exist a large gap in how we train our personnel and how much experience we have in recognizing rapidly evolving fires or other IDLH events (flashover, backdraft, collapse).

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I think you have nailed it and I believe this problem is common throughout the fire service. Ensuring an effective transfer of knowledge and procedure from training environments to the fireground has always been an issue. I have seen this arise time and again over many years. This is one reason why I sincerely believe we should have detailed and documented SOPs that are followed at every incident, where any deviation from a tactical view must be subsequently be accountable. I think FDNY are one of the best at this as their procedures are both detailed and effective, based on years of fireground experience. However, there is always room for improvement.

I think also, that there is a distinct lack of appreciation and understanding of how an enclosed fire is likely to behave under a wide range of conditions amongst many company officers and chiefs.

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=RFDACM02I would say this might be one of the worst ways to vent if you believe a backdraft is imminent. Taking windows for horizontal vent will likely cause the backdraft vs. prevent it, if it is in fact imminent.

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=ChicagoFFOpening the roof is the best way to go. Single story, heavy smoke, why mess with anything else?

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=Shoreman22I was looking at it from the perspective of a low manpower situation, which is what we typically face.

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Venting prior to entry under backdraft conditions is a well known strategy. Vertical vents are made by some and yes, horizontal vents by others. As I say, it is important to read and constantly monitor conditions during any subsequent entry as conditions may quickly deteriorate again.

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=MCaldwellMy thoughts on a pre-flashover condition are to vent the A side window(s) on the Leeward corner only, to draw the fire in one direction. The leeward aspect would hopefully prevent a recirculation of smoke towards or back in the entrance, and perhaps encourage some horizontal venting via venturi.

Our attack would then be made through the main entrance, followed by total ventilation of the A side glass once the initial knockdown has been made.

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I respect your approach to pre-planning by taking high-risk buildings in your area and considering strategy for fire located in different parts of the structure whilst influenced by exterior wind etc. Creating openings to draw fire away from firefighters advancing inside is a known strategy. In theory your suggestion sounds effective and I feel it works with smaller compartmented buildings. I have never used this strategy in a large open planned areas with heavy fire involvement. My belief is that your openings will serve to feed the fire with air and conditions may still deteriorate rapidly.

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* Don't undertake venting actions without a clear objective in mind
* The objective should be both practically viable and achievable
* Don't create openings that are behind or to the side of advancing firefighters in situations where air might feed the fire to escalate rapidly
* Consider that isolating the fire might be more constructive than venting it
* Always anticipate the effects of wind speed and direction prior to making an opening
* Ensure adequate water is available to deal with the involved fire load and any potential for uncontrolled spread before creating vent openings
* Where backdraft conditions are in existence do not cross ventilate an occupied structure

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This is something that goes back to Firefighting 101, as far as backdraft vs flashover is concerned.

Flashover happens when all the material in a compartment reaches its ignition temperature, and all inside the compartment is consumed with fire. Its warning signs are extremely high temperature, not being able to withstand temps unless all the way on the ground, "driven to the floor". It can be prevented by "pencilling" the ceiling with quick bursts of a straight stream, which will cool the high temps, but can disrupt the thermal balance, and lead to steam burns. Also, venting the involved compartment will allow the gases to escape, cooling the area, and allowing the Engine Co. to get closer.

Backdraft happens when all the oxygen is used up by a fire. The temps remain extremly high in the compartment, but with the exclusion of a single element from the fire tetrahedron (heat, fuel, self sustaining chain reaction, and oxidizer), namely O2, the fire goes out. With the reintroduction of O2 into an area with all the other elements in the fire tetrahedron, a rapid oxidation process happens.....Backdraft. The only real way, that I know of the prevent a Backdraft from kicking off, is vertical ventilation. However, in some buildings, after a sustained period of fire, I am not sure how feasible this would be, such as lightweight buildings, Eg. Type II construction.

Gentlemen, if there are errors in my analyzing of the situation, please, beat me gently :p :D

Paul;
with the type of building you are describing, the IC may rule out vert. venting. Would making out OWN openings on the Charlie side be feasible? This is of course, is if it is feasible that we could make them in the first place.
For example, a pre-fab structure, corragated metal, with bowstring truss roof with same conditions you describe. Would placing an OVM with a K12 saw in the Charlie side to make his own openings work?

Just throwing out an idea........:rolleyes:

BLSboy - Yes your text book analysis of Flashover and Backdraft phenomena is exactly that .... 'text book' ;) But in reality there are many more aspects from a practical point of view.

• Flashover is mainly heat-induced
• Backdraft is mainly air (oxygen) induced
• Flashover may also be induced by air being fed into the fire area
• Pencilling a straight stream is one way (but not the best way) of tackling flashover conditions
• Effectively pulsing water-fog will not upset the thermal layer
• In such a large open plan area with even an average fire load, a well involved developing fire is not likely to be controlled by hand-lines alone
• Backdraft conditions in small compartments or buildings may also be tackled using indirect water-fog from the exterior
• Any openings on the C side as you discuss might be difficult to create and not offer us too much more in way of a tactical advantage

If I remember correctly, 20 years ago Chief Vincent Dunn expressed in a lecture he was giving on rollover and flashover, that venting store front windows should be delayed as long as possible, or not attempted during offensive operations. He suggested considering the location of a fire, in relation to the window openings, in a building with a higher ceiling. The fire itself will be present once it grows, along with the heat and gases, at the ceiling level. Opening store front windows, horizontally venting, allows air in below the fire. If you consider the theoretical model of the pot belly stove it's quite apparent what he meant. He summed it up by saying it is a difficult decision for a fire officer to determine when horizontal ventilation would be more of a detriment than a benefit. I took away from the class that there is a point in a fires growth when horizontal venting allows fresh air in to feed the fire, and the horizontal opening that was created cannot effectively release the resulting growth of the fire.

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Originally Posted by PaulGRIMWOOD

BLSboy - Yes your text book analysis of Flashover and Backdraft phenomena is exactly that .... 'text book' ;) But in reality there are many more aspects from a practical point of view.

• Flashover is mainly heat-induced
• Backdraft is mainly air (oxygen) induced
• Flashover may also be induced by air being fed into the fire area
• Pencilling a straight stream is one way (but not the best way) of tackling flashover conditions
• Effectively pulsing water-fog will not upset the thermal layer
• In such a large open plan area with even an average fire load, a well involved developing fire is not likely to be controlled by hand-lines alone
• Backdraft conditions in small compartments or buildings may also be tackled using indirect water-fog from the exterior
• Any openings on the C side as you discuss might be difficult to create and not offer us too much more in way of a tactical advantage

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Paul, now that you mention it, IIRC, I recall a story of 2 Brothers out in Co, I think, that died in a SFD, after the fire was pretty much under control. Someone popped a window where they shouldnt have, fire got a nice deep breath, and flashed.


But, from your Point of view, which would be the best way to tackle ventilation for this scenerio?

BLSboy I think Delta's post on Chief Dunn's lecture from 20 years ago says it all for me and I find myself totally in agreement with this general strategy. However, I would suggest that for much smaller stores the strategy might actually reverse. Under such fire conditions, I would probably prefer to remove the windows (at a high level) prior to entry, allowing a good few seconds for conditions to develop or stabilize, prior to committing firefighters inside.

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Originally Posted by DeltaCreek

If I remember correctly, 20 years ago Chief Vincent Dunn expressed in a lecture he was giving on rollover and flashover, that venting store front windows should be delayed as long as possible, or not attempted during offensive operations. He suggested considering the location of a fire, in relation to the window openings, in a building with a higher ceiling. The fire itself will be present once it grows, along with the heat and gases, at the ceiling level. Opening store front windows, horizontally venting, allows air in below the fire. If you consider the theoretical model of the pot belly stove it's quite apparent what he meant. He summed it up by saying it is a difficult decision for a fire officer to determine when horizontal ventilation would be more of a detriment than a benefit. I took away from the class that there is a point in a fires growth when horizontal venting allows fresh air in to feed the fire, and the horizontal opening that was created cannot effectively release the resulting growth of the fire.

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