PPV for exposure control

[Geinandputitout]

I read the following statement in a SOP in regard to PPV & exposure control.
Once smoke has cleared, the exit should be closed, the building
sealed, so that it will "over pressurize" the exposure. Over pressurized air will force hot gases back across the beaches, or back
down common attic spaces towards the fire area. This can prevent fire spread extension.
The second most critical exposure would then receive PPV in a similar manner.
The next priority would be the fire occupancy.

Does anyone have any experience doing this? Does it work?

[DeputyMarshal]

I read the following statement in a SOP in regard to PPV & exposure control.
Once smoke has cleared, the exit should be closed, the building
sealed, so that it will "over pressurize" the exposure. Over pressurized air will force hot gases back across the beaches, or back
down common attic spaces towards the fire area. This can prevent fire spread extension.
The second most critical exposure would then receive PPV in a similar manner.
The next priority would be the fire occupancy.

Does anyone have any experience doing this? Does it work?

Air isn't going to go anywhere unless it is flowing from high pressure to low pressure.

You can't pressurize a "sealed" building. Assuming that the intent is to close all building openings except the one being used for PPV, pressurizing the building is just going to force air out of the building through whatever breaches it can find. Those breaches may be the ones related to the fire or they may be through areas previously untouched by the fire. IOW, if you aren't controlling the escape of air and products of combustion you may very well be pushing it right into your exposures.

If you are doing PPV, you want to control two kinds of openings: openings where you're supplying positive pressure to push air in and openings where you want that pressure and entrained products of combustion to come out. You need both openings for PPV to do anything useful.

[Dalmatian190]

Over pressurized air will force hot gases back across the beaches, or back
down common attic spaces towards the fire area. This can prevent fire spread extension.


For the love of all that is holy...

I hope you either grossly mis-read that SOP...

Or you grossly mis-typed that SOP...

And I'm one of the supporters of appropriately used PPV here!

Translation of the line above: Use positive pressure in a common void space in a building with an uncontrolled fire.

Is the purpose to that SOP to deliberately create blowtorch conditions pushing the fire back into the faces of the hose team attacking the seat? (And we warn about opposing hose streams pushing fire on crews...)

Or is simply to burn the roof off quicker so the ladder pipes can go to work 30 minutes sooner?

[Geinandputitout]

Read it and weep?

http://phoenix.gov/fire/20212d.pdf

Bottom of page 2

[DeputyMarshal]

Bottom of page 2

That doesn't say what the SOP you provided says. That may be what it was intended to say but it isn't what it actually says.

The Phoenix SOP works. (The whole SOP taken together including the important tactical considerations listed near the top of page 1. Those considerations still apply to what's written near the bottom of page 2.)

The SOP at the beginning of the post by itself doesn't make any sense to me. Hopefully other steps and considerations are intended but didn't make it into the written version of the SOP.

[Geinandputitout]

...

Well of course the SOP taken as a segment doesn't provide the entire picture. No sentence out of any SOP would...

Back to the original post. Has anyone ever used this tactic and what was the result?

[Edward Hartin]

Defensive PPV

We have used this tactic quite successfully on many occasions. However, a few thoughts and words of caution.

What is being described is 1) sequential ventilation to clear a smoke logged exposure, and 2) pressurization of an uninvolved space to prevent further infiltration of smoke. The first is a ventilation tactic and the second is a confinement tactic that I call "anti-ventilation" (a term borrowed from the Swedes).

Concern with pushing fire on the attack crews is not justified. What you are doing is pressurizing a sealed space, not moving air (as you would in PPV). However, I would be wary of using this tactic in situations where fire has extended to common (to the fire occupancy and exposure) void spaces.

An example: We had an apartment fire on Floor 2 of a two-story, wood-frame building last night. Companies arrived with persons reported in the fire unit. A rapid attack on the fire and quick primary search controlled the fire and determined that no occupants were present. The fire unit and adjacent unit on Floor 2 were both smoke logged. PPV was used to clear the smoke from the adjacent unit and it was then pressurized to prevent further infiltration of smoke. Concurrently, PPV was used to clear smoke from the fire unit.

As with all ventilation and anti-ventilation tactics, the key is understanding fire behavior and effectively integrating ventilation and fire control tactics.

Cheers,

[FFFRED]

http://phoenix.gov/fire/20212d.pdf

Bottom of page 2

More poor tactics from the same inexperienced clowns who can't maintain company integrity, or standardized assignments at a job and insist that fog nozzles should be used off standpipes for safety reasons!

If your objective is to force fire throughout the cockloft and loose the entire block...then by all means follow this advice.

If you value your life and the lives and property of others, I would treat everything they say with a grain of salt.

FTM-PTB

PS- I did read it and I did weep this is a prime example of the leadership some men have to deal with....at least when they aren't on the seminar circut.

[ThNozzleman]

You can't pressurize a "sealed" building.

Sure you can. I think you guys missed the point of the exposure being the building that is pressurized with the fan, not the burning building.

[DeputyMarshal]

Sure you can.

No, you cannot. You need at least one controlled opening to add pressure. Tie a knot in the neck of a balloon and then try to inflate it and you'll see what I mean.

(Unless, of course, you have some method of lowering the pressure of the entire space surrounding the "sealed building" thus increasing the relative pressure inside.)

The point is that the SOP, as presented, is vague. I'm sure that there is some legitimate purpose behind it but that purpose and the means to achieve it didn't make it into the written SOP.

[dmleblanc]

I am assuming that the "exposure" you are speaking of would be an area or occupancy that is actually physically attached to the fire area? Say, another occupancy sharing a common attic or cockloft? If that is so, I could see the tactic having some merit, if, and only if, you are certain of where the fire is and therefore where it is going to go.

It would seem to me that if you can pressurize the uninvolved areas, you will force the fire and products of combustion to stay out of those areas. However, as with any use of PPV, you will need to make sure that you are not pushing those gases to OTHER currently uninvolved areas (like, the attached exposure on the other side of the fire )

As for myself, I can't speak with experience here, because we have very few multiple occupancy buildings. What I consider an "exposure" is the building next door, i.e., physically apart from the fire building. Therefore, our experience with PPV has been limited to ventilating the actual fire building.

[mcaldwell]

The principle is the same as how every modern commercial residential/hotel or high-rise air handling system works.

In a large building, the air handlers provide the PP, usually in the stairwell first, then through the hallways, and finally exiting the building through the units. In a "perfect" fire scenario, this keeps the stairwells clear of smoke, confines it to the hallway of origin, and hopefully the unit or room as well.

I see this as just being the artificial method of creating the same system once we have compromised the buildings mechanical ventilation (by alarm interconnect or manually killing power), or physical restrictions (by propping doors, etc).

Of course it needs some care, like all PPV, but the idea works. You are not moving masses of air within the building, just creating a small pressure differential. The PP airstream rapidly loses velocity in a stairwell or long hallway. In our training, we regularly pressurize the upper floors of our hotels this way, and there is no noticable "wind" on the upper floors, but the smoke (artifical in our scenarios) does easily move away from the PP ventilated area.

If you are using this in close proximity to the fire, and in conflict with interior ops, you are certainly asking for trouble.

[FFFRED]

I am assuming that the "exposure" you are speaking of would be an area or occupancy that is actually physically attached to the fire area? Say, another occupancy sharing a common attic or cockloft? If that is so, I could see the tactic having some merit, if, and only if, you are certain of where the fire is and therefore where it is going to go.

It would seem to me that if you can pressurize the uninvolved areas, you will force the fire and products of combustion to stay out of those areas. However, as with any use of PPV, you will need to make sure that you are not pushing those gases to OTHER currently uninvolved areas (like, the attached exposure on the other side of the fire )

As for myself, I can't speak with experience here, because we have very few multiple occupancy buildings. What I consider an "exposure" is the building next door, i.e., physically apart from the fire building. Therefore, our experience with PPV has been limited to ventilating the actual fire building.

In a taxpayer/stripmall any adjoining occupancies within the building are exposures as are any buildings on side 2,3(dependant on distance) or 4. At least in any reference text or in practice anywhere I've ever seen.

FTM-PTB

[dmleblanc]

In a taxpayer/stripmall any adjoining occupancies within the building are exposures as are any buildings on side 2,3(dependant on distance) or 4. At least in any reference text or in practice anywhere I've ever seen.

FTM-PTB

I realize that....I'm just saying that we don't have many occupancies that fit that description (like maybe 2 buildings in our area), and we've never had a fire in one.

[FFFRED]

I realize that....I'm just saying that we don't have many occupancies that fit that description (like maybe 2 buildings in our area), and we've never had a fire in one.

10-4

FTM-PTB