1. #1
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    Question Positive Pressure... neighbours' house?

    Eh guys. Talking to a buddy of mine on the job and he was telling me how one of their emerging protocols is to actually pressurize the homes on each side of an involved structure. They have no problems getting the equipment on scene and no shortage of manpower... but I haven't heard of such a tactic.

    Just wondering if anyone had any opinion on it? Any feedback? Success or failure stories?
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    Sort of makes sense in theory... if you PPV the adjacent exposures then heat and smoke would not be able to enter, especially if it shares walls like rowhomes or strip malls. It is like a pressurized stairwell in a high rise. Interesting, have to watch this and see if anything comes of it.
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    Up in the Great White North, I imagine you'd only want to do this sort of thing in the summer... you know, that two weeks in august, where it gets over 65.

    I am now a past chief and the views, opinions, and comments are mine and mine alone. I do not speak for any department or in any official capacity. Although, they would be smart to listen to me.

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    We do it from time to time. Just like doing ppv but without an exhaust point. I read something about this tactic a while back, ill see if I can dig it up.

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    I used ppv on an exposure with a common wall. Had a crwe inside the exposure monitoring conditions at all times. Alsothere were no breeches in the wall. Kept the heat build up down,
    ?

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    I've seen this tactic explained in a NFA STICO class, but only in relation to row homes or attached town homes. Basically, you use PPV to pressurize the units on either side of the fire unit, with no escape for the pressure. The idea is to help keep the fire contained to the fire unit. I have not had a chance to use this tactic or see it used, but it makes some sense to me. However, I wouldn't waste time doing it, but if you're covered up in manpower and equipment, I think it would be a reasonable thing to try.

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    With regards to this tactic being used in attached and row frame houses, this concept has its roots from the Navy/Coast Guard.

    As part of standard Engineering actions on the report of a fire, the surrounding fire zones, and/or spaces are set with positive ventilation (supply fans on high, exhaust fans off or slow if possible) while negative ventilation is set in the affected compartment (supply off, exhaust on high).

    It is incredibly effective at keeping the smoke in the surrounding area, mainly when smoke boundries are opened up for personal access.
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    To clarify - we had an exit vent - the intent was two fold - one to some what pressurise the exposure building - and two, to remove the smoke and heat build up (radiant heat) - I want to emphasise the common wall (masonry) was not breeched.
    ?

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    Sounds like a good tactic. I've fought a couple fires in a small town square where the buildings use common walls. I believe this would of kept the fire from breeching the red brick common wall. I'd like to learn more as this is still a threat in our district.

    P.S. ---See good conversation still exists here.

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    Never would have thought PPV would be taken to this level: Exposure Protection? I can buy the "concept" of attached row houses, but I'd be very wary about unknown openings. If the pressure is finding one way out, it may be drawing at another point (venturi?). PPV is all about fully controlling the flow or lack of flow of air, too often we find voids and other hidden features too late. Of course as always I'm a huge skeptic of PPV in the Northeast, where significant amounts of construction allows for large voids and the climate requires occupants to regulate their inside temperature using windows, fans and closing off portions of the house. All of this make for a much more questionable path of pressurized air travel.

    As for using PPV in a separate structure? I believe it'd be a total waste of resources and time. When the curtains ignite due to radiant heat, that pressurized air current will really work great!

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    Quote Originally Posted by RFDACM02 View Post
    As for using PPV in a separate structure? I believe it'd be a total waste of resources and time. When the curtains ignite due to radiant heat, that pressurized air current will really work great!
    I tend to agree. I'm not sure what they'd be trying to accomplish with such a tactic.
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    Quote Originally Posted by RFDACM02 View Post
    Never would have thought PPV would be taken to this level: Exposure Protection? I can buy the "concept" of attached row houses, but I'd be very wary about unknown openings. If the pressure is finding one way out, it may be drawing at another point (venturi?). PPV is all about fully controlling the flow or lack of flow of air, too often we find voids and other hidden features too late. Of course as always I'm a huge skeptic of PPV in the Northeast, where significant amounts of construction allows for large voids and the climate requires occupants to regulate their inside temperature using windows, fans and closing off portions of the house. All of this make for a much more questionable path of pressurized air travel.

    As for using PPV in a separate structure? I believe it'd be a total waste of resources and time. When the curtains ignite due to radiant heat, that pressurized air current will really work great!
    Would assume that the tactic is used in conjunction with proper PPV on the property on fire also. This would mean having the back side of the fire to be vented, so any additional airflow from the adjoining structures being over pressured would vent out the same backside vent. In theory. Never used this tactic, but for adjoining structures it does make some sense.

    For exposures to a separate structure I agree, think this would be counterproductive, actually pretty risky, for once the curtains do catch on fire you have an improper PPV'd building charged with clean air.
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    I can see the theory on MFD (multi-family dwellings) and in my mind can actually see this working well. Never tried it though... Seems pretty simple and a good way to contain a fire to the occupancy of origin. Next time we are at our Tower, I'm gonna set it up and check this out.

    Great post and great conversation.
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    I could see this on attached structures, similar to the fire protection systems used in many large buildings such as high rises. I can't see a use for it in unattached exposures.

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    Quote Originally Posted by mikeyboy View Post
    I can see the theory on MFD (multi-family dwellings) and in my mind can actually see this working well. Never tried it though... Seems pretty simple and a good way to contain a fire to the occupancy of origin. Next time we are at our Tower, I'm gonna set it up and check this out.

    Great post and great conversation.
    I doubt a drill tower is going to give you real world results on extension? The real hazard is the unknown openings and voids caused by occupants or contractors. Also, one failed window in an exposure occupancy changes the pressurization and suddenly you may be pulling a draft for the very small openings you were previously pushing air out of. The problem I see in general is super charging hte uninvolved area with air, when if some fire does make it in, you'd better know it and be able to react accordingly very quickly.

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    Very true, however the Drill Tower is all we have without burning down an occupied building or multi-family dwelling. LOL. I posted that and will try it to get the "basic fundamentals" of the theory. Since I came-up with that idea I have it figured-out in my head how we can set the Tower up to try this; when I get back to work I will visit the Tower and see if "reality" agrees with what I have in my "ole pea brain."

    Thanks for the increase in the challenge though... I'll post if I am able to make it work.
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    Good tactic in theory.

    May be valuable in our few strips malls if we ever get an incident there.

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    I have heard of this tactic before but never tried it. I seem to remember it in the positive presure attack book from the guys from salt lake. (i cant remember their names)

    Increasing the pressure in the attached exposure would prevent the smoke and heat from traveling to that area. In my mind the air in the exposure occupancy (higher pressure) would flow to the air in the fire occupancy (lower pressure). In theory this would prevent the smoke/heat travel into that area so voids would not be an problem the air is traveling to the fire area. this sounds very simialar to PPV in stairwells in highrise buildings a commonly used tactic. I am thinking it is used to lessen smoke travel versues flame spread.

    I would think that a failure of a window in the exposure area could cause a problem if not address. By creating a draft, and drawing the fire to the exposure. However shutting a door or just cutting the fan off would solve that issue.

    RFDACM02- I am confused on the comment about cramming the exposure occupancy with clean air. What problem would that cause. the only way that would increase a fire is if the oxygen level in the air some how increased above 21%. With no exit for the air; the air is not going to "flow". if the fire does penitrate the fire wall and get into the exposure, it is no longer and exposure. Just cut the fan off and put the fire out. Either way you always need a crew inside the exposure to monitor the conditions and fire spread.

    I am thinking this is along the same lines as the newer air track management theories that are invading out shores from europe. I have learned alittle about it, understand the concepts. However question the real world application of it.

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    Quote Originally Posted by RFD21C View Post

    RFDACM02- I am confused on the comment about cramming the exposure occupancy with clean air. What problem would that cause. the only way that would increase a fire is if the oxygen level in the air some how increased above 21%. With no exit for the air; the air is not going to "flow". if the fire does penitrate the fire wall and get into the exposure, it is no longer and exposure. Just cut the fan off and put the fire out. Either way you always need a crew inside the exposure to monitor the conditions and fire spread.
    My skepticism is more with the sudden failure of a window in that exposure or with a failure of the separation. When an unintended opening occurs, it must be noticed and reacted to, for someone shut off the fan. Any delay in this I'd fear might increase fire intensity. I'm not convinced the pressurized air addresses the most common routes of exposure. I think successes of this tactic may not be able to be validated, as they may have been actual success of proper separation in the first place. I guess there's value on preventing smoke spread though, so in that there's some validity.

    As I said, I'm a skeptic of PPV in many cases, and this seems like a an extrapolation of a only somewhat proven tactic. I know it works when it works, but so do water curtains. Both fail miserably, when they fail too.

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    Quote Originally Posted by RFDACM02 View Post
    As I said, I'm a skeptic of PPV in many cases, and this seems like a an extrapolation of a only somewhat proven tactic. I know it works when it works, but so do water curtains. Both fail miserably, when they fail too.
    I couldnt agree more, I have the scares to prove it. from the use of positive pressure in an ordinary construction cape cod. Like I said above i dont think this tactic is put the fan at the door to the exposure and walk away. my view it is used in conjuntion with a engine and truck crew in the building to check for extension and monitor the fire wall. popping inspection holes and pulling ceiling is still needed. Hose line at the ready. My thought is it would be useful in preventing the smoke spread to the exposure to reduce the damage. even if a window fails and goes unnoticed if the exposure crews are babysitting the fire wall like they are suppose to they can hit the fire when it start to breach it and is still managable.

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    Quote Originally Posted by RFDACM02 View Post
    As I said, I'm a skeptic of PPV in many cases, and this seems like a an extrapolation of a only somewhat proven tactic. I know it works when it works, but so do water curtains. Both fail miserably, when they fail too.
    FWIW, PPV used properly is a very effective tactic. The problem is, I've seen a lot of totally botched attempts at PPV. "Water curtains," OTOH, don't work at all.
    Last edited by DeputyMarshal; 12-27-2010 at 09:48 PM. Reason: typo
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    Quote Originally Posted by FireFuss View Post
    That building is standing today because of 40 or so sprinkler heads outside on the adjoining wall. They were pressurized by an engine, and acted as a sort of wall mounted water curtain.
    Direct cooling by wetting an exposure works just fine; a traditional "water curtain" between the fire and the exposure does not.
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    Our water curtain appliance is designed to tilt so it can flow across the surface.
    ?

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    And back to the original question - it worked well in our situation , the only thing I would have done differently ,would to be have someone stationed at the fan to kill it if there was a wind shift or an inversion of some sort. This was an extermely smokey fire and took a long time to self vent. (multiple roofs /ceilings ) we also had gone completely defensive when we initated the ppv on the exposure and had two lines and a portion of the drop ceiling down to monitor the entire wall. (no vents in the flat roof)The fan was in the C/D corner of the exposure building (one story)and the vent was the front door on the A side of the exposure.
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    I think a lot of FF's lose track of two things about PPV. One: It's a TOOL. Two: That TOOL should have an OPERATOR with it and it DOES have a THROTTLE which DOES NOT necessarily have to be set at full throttle. I LIKE PPV's, have used them on various building constructions. Used with DISCRETION they can speed up your work and make your life EASIER, Used IMPROPERLY: Hello PARKINGLOT! T.C.

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