1. #26
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    Quote Originally Posted by Rescue101 View Post
    I LIKE PPV's
    Minor nit-pick: PPV is a tactic, not a tool. This tactic is usually implemented using a fan (tool) -- either gasoline powered or electric -- but can occasionally even be accomplished by taking advantage of a convenient wind.

    I do agree with your overall assessment.
    "Nemo Plus Voluptatis Quam Nos Habant"

    The Code is more what you'd call "guidelines" than actual rules.

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    Quote Originally Posted by DeputyMarshal View Post
    Minor nit-pick: PPV is a tactic, not a tool. This tactic is usually implemented using a fan (tool) -- either gasoline powered or electric -- but can occasionally even be accomplished by taking advantage of a convenient wind.

    I do agree with your overall assessment.
    I agree with your assessment. For the purposes of the THREAD however,I DON'T think the OP was thinking Mother Nature PPV. T.C.

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    Sounds like it helped slack
    Last edited by 6Duron1; 12-29-2010 at 02:46 PM.

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    Pressurizing an exposure is VERY effective.

    I have used it and had success on the following exposures; strip malls, a dwelling w/ attached garage and adjacent high rise floors.

    The higher the interior pressure, the more effective it will keep fire out!

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    Quote Originally Posted by J.Beck View Post
    Pressurizing an exposure is VERY effective.
    You might want to reread the initial post. The OP appears to be talking about detached exposures.
    "Nemo Plus Voluptatis Quam Nos Habant"

    The Code is more what you'd call "guidelines" than actual rules.

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    Quote Originally Posted by DeputyMarshal View Post
    You might want to reread the initial post. The OP appears to be talking about detached exposures.
    I probably did misunderstand the OP, although, the point remains the same - pressurizing an exposure, attached or not, is VERY effective.

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    Quote Originally Posted by J.Beck View Post
    I probably did misunderstand the OP, although, the point remains the same - pressurizing an exposure, attached or not, is VERY effective.
    For a detached exposure, effective at doing what?
    "Nemo Plus Voluptatis Quam Nos Habant"

    The Code is more what you'd call "guidelines" than actual rules.

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    Quote Originally Posted by DeputyMarshal View Post
    For a detached exposure, effective at doing what?
    Eliminating fire spread to the given exposure.

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    Quote Originally Posted by J.Beck View Post
    Eliminating fire spread to the given exposure.
    How do you propose that pressurizing a detached exposure will prevent fire spread given that fires typically spread to detached exposures either by radiant heat or direct flame contact; neither of which is effected by pressurization?
    "Nemo Plus Voluptatis Quam Nos Habant"

    The Code is more what you'd call "guidelines" than actual rules.

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    Quote Originally Posted by DeputyMarshal View Post
    How do you propose that pressurizing a detached exposure will prevent fire spread given that fires typically spread to detached exposures either by radiant heat or direct flame contact; neither of which is effected by pressurization?
    Pressurization has everything to do with keeping out direct flame contact and radiant heat.

    As fire spreads it seeks to go to a neutral or negative pressure (outside air, non-pressurized buildings, etc). Fire will not spread where there is a positive pressure, thus the reason for pressurizing exposures.

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    Quote Originally Posted by J.Beck View Post
    Pressurization has everything to do with keeping out direct flame contact and radiant heat.
    Pressurization has zero effect on both of those modes.

    As fire spreads it seeks to go to a neutral or negative pressure (outside air, non-pressurized buildings, etc). Fire will not spread where there is a positive pressure, thus the reason for pressurizing exposures.
    Pressurizng a detached exposure does nothing to prevent either radiant heat or direct flame contact from igniting its exterior. If you want to keep a detached exposure from igniting, keeping heat/fire off of its exposed surfaces is typically going to be a far superior strategy to pressurizing it.
    "Nemo Plus Voluptatis Quam Nos Habant"

    The Code is more what you'd call "guidelines" than actual rules.

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    Quote Originally Posted by DeputyMarshal View Post
    Pressurization has zero effect on both of those modes.
    Pressurizng a detached exposure does nothing to prevent either radiant heat or direct flame contact from igniting its exterior. If you want to keep a detached exposure from igniting, keeping heat/fire off of its exposed surfaces is typically going to be a far superior strategy to pressurizing it.
    Of course traditional exposure protection via. charged handlines must by utilized for proper exterior exposure protection. But, to protect the entire(interior/exterior) structure, pressurization must also be utlized.

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    Quote Originally Posted by J.Beck View Post
    Of course traditional exposure protection via. charged handlines must by utilized for proper exterior exposure protection. But, to protect the entire(interior/exterior) structure, pressurization must also be utlized.
    If you protect the exterior the interior isn't a primary exposure.

    Of course, if you have the luxury of excess manpower standing around with nothing better to do, go for it...
    "Nemo Plus Voluptatis Quam Nos Habant"

    The Code is more what you'd call "guidelines" than actual rules.

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    Quote Originally Posted by J.Beck View Post
    Fire will not spread where there is a positive pressure, thus the reason for pressurizing exposures.
    Good lord, do you understand basic fire behavior or heat transfer? How does PP affect radiant heat transfer or conductive transfer?

    It's amazing that more of us haven't burned down blocks ignoring the use of positive pressure on exposures. Where I live, if the positive pressure can protect a house, they probably would rather have it burn then pay the heating bill.

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    Quote Originally Posted by DeputyMarshal View Post
    If you protect the exterior the interior isn't a primary exposure.

    Of course, if you have the luxury of excess manpower standing around with nothing better to do, go for it...
    Capiche.


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    Quote Originally Posted by J.Beck View Post
    Of course traditional exposure protection via. charged handlines must by utilized for proper exterior exposure protection. But, to protect the entire(interior/exterior) structure, pressurization must also be utlized.
    You could also use land use/fire codes to ensure exposures were not an issue in the first place. This in fact would actually be more complete protection, though likely slightly less realistic than your inflatable fire protection bubble?

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    Quote Originally Posted by RFDACM02 View Post
    Good lord, do you understand basic fire behavior or heat transfer? How does PP affect radiant heat transfer or conductive transfer?

    It's amazing that more of us haven't burned down blocks ignoring the use of positive pressure on exposures. Where I live, if the positive pressure can protect a house, they probably would rather have it burn then pay the heating bill.
    I have no idea what you are talking about in your second paragraph. So I will address the first one only.

    Talking specifically about fire spread and fire behavior; fire will move to an area of lower pressure, it is simple science and is backed up by NIST. I am not sure how else to explain this concept to you. "Radiant heat transfer" and "conductive transfer" are severely limited by PPA due to decreases in compartment temperature. For every 18 degrees dropped in temperature, combustibility is decreased by 50%. Thus, disrupting a portion of the fire tetrahedron and decreasing the potential for fire spread.
    Last edited by J.Beck; 12-29-2010 at 06:14 PM.

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    Quote Originally Posted by RFDACM02 View Post
    You could also use land use/fire codes to ensure exposures were not an issue in the first place. This in fact would actually be more complete protection, though likely slightly less realistic than your inflatable fire protection bubble?
    It is not my concept. It is something that initially I severely disagreed with and set out to prove wrong...well, here I am 50+ burns later and I am the biggest PPA advocate there is.

    Don't believe it?

    Prove it wrong.
    Last edited by J.Beck; 12-29-2010 at 06:17 PM.

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    Quote Originally Posted by J.Beck View Post
    I am not sure how else to explain this concept to you.
    Seriously? You might want to start by gaining a better understanding yourself.

    "Radiant heat transfer" and "conductive transfer" are severely limited by PPA due to decreases in compartment temperature.
    1) Positive pressure won't significantly lower compartment temperature in an exposure unless it's because it's cold outside and you have the door open for PPV.

    2) Radiant heat transfer is unaffected by ambient air pressure or temperature.

    3) Conductive heat transfer isn't greatly affected by the minor variations in temperature you might get pressurizing an exposure.

    4) Direct flame contact to a wall is unaffected by the pressure on the other side of the wall.

    For every 18 degrees dropped in temperature, combustibility is decreased by 50%.
    I have no idea where you're getting this information. A material's ignition temperature is unaffected buy the temperature of its surroundings. (Not that PPV is going to significantly alter the ambient temperature of an exposure building.)

    Thus, disrupting a portion of the fire tetrahedron and decreasing fire spread.
    Even assuming PPV in this scenario has any useful effect on the inteior of the exposure building, it has no effect whatsoever on the part of the exposure building actually in danger of ignition; the exterior of the building exposed to the fire in the neighboring structure.

    PPV and PPA certainly have tactical benefits -- in the fire building. In a detached exposure? Not so much.
    "Nemo Plus Voluptatis Quam Nos Habant"

    The Code is more what you'd call "guidelines" than actual rules.

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    Quote Originally Posted by DeputyMarshal View Post
    Seriously? You might want to start by gaining a better understanding yourself.



    1) Positive pressure won't significantly lower compartment temperature in an exposure unless it's because it's cold outside and you have the door open for PPV.

    2) Radiant heat transfer is unaffected by ambient air pressure or temperature.

    3) Conductive heat transfer isn't greatly affected by the minor variations in temperature you might get pressurizing an exposure.

    4) Direct flame contact to a wall is unaffected by the pressure on the other side of the wall.



    I have no idea where you're getting this information. A material's ignition temperature is unaffected buy the temperature of its surroundings. (Not that PPV is going to significantly alter the ambient temperature of an exposure building.)



    Even assuming PPV in this scenario has any useful effect on the inteior of the exposure building, it has no effect whatsoever on the part of the exposure building actually in danger of ignition; the exterior of the building exposed to the fire in the neighboring structure.

    PPV and PPA certainly have tactical benefits -- in the fire building. In a detached exposure? Not so much.
    PPA and PPV are not the same and we both (mostly me), seem to be bleeding over both concepts. Much of my later responses (responder to another poster) deal specifically with PPA concepts; i.e. temperature decrease, etc. While yours seem to be focusing more on PPV and exposure protection (The OP).

    Unfortunately, I am out of time to give you back a response that your post deserves. I will get back with you tomorrow.

    Thanks.

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    Quote Originally Posted by J.Beck View Post
    While yours seem to be focusing more on PPV and exposure protection (The OP).
    Which would seem appropriate since it is, after all, the subject under discussion.

    Unfortunately, I am out of time to give you back a response that your post deserves. I will get back with you tomorrow.
    Stay safe, Cap'!
    "Nemo Plus Voluptatis Quam Nos Habant"

    The Code is more what you'd call "guidelines" than actual rules.

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    OK. Where were we?!

    Talking specifically about using positive pressure as exposure protection on an un-attached structure. Correct?

    I don't know how else to explain this concept to you..

    Pressurizing the interior of a structure makes it more difficult for fire and smoke to enter it. Pressurization can provide an excellent means of protection for buildings or other areas exposed to adjacent fires. This method works whether the exposure is an entire structure or a partitioned area in the same structure, such as a business in a strip mall, a home with an attached garage, or a single floor in a high-rise. Under these conditions it's not necessary to make an exhaust opening as we are attempting to create the highest possible pressure within the exposure to keep heat, smoke and fire out.

    Can and should a handline also be deployed to an effected exposure? Yes, of course, for the ultimate exposure protection they should be used in conjunction. In fact, I used thesetechniques together today while at a working structure fire...worked great!

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    Quote Originally Posted by DeputyMarshal View Post
    I have no idea where you're getting this information. A material's ignition temperature is unaffected buy the temperature of its surroundings. (Not that PPV is going to significantly alter the ambient temperature of an exposure building.)
    Talking specifically about PPA, NOT exposure protection.

    Ventilation removes heat. As heat is removed, it slows the ignition of potential fuels. The fact that for every decrease of 18 degrees the speed of the chemical reaction leading to combustibility decreases 50% is talked about extensively in the "Campbell Prediction System", which certainly you are familiar with.

    Either way,

    The Campbell Prediction System (CPS) is a practical way to use on-scene fire behavior observations in order to determine fire behavior strategies and tactics. A combination of scientific research and the knowledge of the successful firefighters' methods and practices are utilized to explain fire behavior. In these situations the observed fire behavior becomes the baseline for fire behavior predictions. A special logic replaces intuition allowing an explanation of how tactics are developed. Developing a strong case for acting on the fire's potential rather than waiting for the fire to make the change would save many of the lives lost because firefighters reacted too late. If people could explain what the potential of the fire is in their situation, few accidents would happen. The Campbell Prediction System provides the logic and language to do so.

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    Quote Originally Posted by J.Beck View Post
    Pressurizing the interior of a structure makes it more difficult for fire and smoke to enter it.
    Smoke and fire entering a detached exposure aren't generally among the biggest threats of ignition.

    This method works whether the exposure is an entire structure or a partitioned area in the same structure, such as a business in a strip mall, a home with an attached garage, or a single floor in a high-rise.
    I'm not disputing the value of the technique in attached exposures -- just detached ones.

    Can and should a handline also be deployed to an effected exposure? Yes, of course, for the ultimate exposure protection they should be used in conjunction.
    And that hoseline applied to the outside of the detached exposure will do far more good than pressurization of the inside, IMHO.
    Last edited by DeputyMarshal; 12-30-2010 at 10:53 PM. Reason: typo
    "Nemo Plus Voluptatis Quam Nos Habant"

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    Quote Originally Posted by J.Beck View Post
    Talking specifically about PPA, NOT exposure protection.
    That's a different subject altogether. I'd prefer to stick with the thread's topic.

    The fact that for every decrease of 18 degrees the speed of the chemical reaction leading to combustibility decreases 50% is talked about extensively in the "Campbell Prediction System", which certainly you are familiar with.
    I've heard of it in conjunction with wildfire firefighting. I don't recall ever seeing anyone attempt to apply it to structural firefighting nor would I expect it to be relevant to it.
    "Nemo Plus Voluptatis Quam Nos Habant"

    The Code is more what you'd call "guidelines" than actual rules.

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