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  • #46
    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!
    Cognition before Ignition

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    • #47
      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.
      Cognition before Ignition

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      • #48
        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, 10:53 PM. Reason: typo
        "Nemo Plus Voluptatis Quam Nos Habant"
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        The Code is more what you'd call "guidelines" than actual rules.

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        • #49
          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"
          sigpic
          The Code is more what you'd call "guidelines" than actual rules.

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          • #50
            Originally posted by DeputyMarshal View Post
            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.
            No attempt to apply the CPS to structural firefighting? Not relevant?

            http://www.pennwellbooks.com/popratforfiv.html

            The authors use the 18 degree/50% drop in combustibility extensively in their well respected book.
            Cognition before Ignition

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            • #51
              Originally posted by J.Beck View Post
              No attempt to apply the CPS to structural firefighting? Not relevant?

              http://www.pennwellbooks.com/popratforfiv.html

              The authors use the 18 degree/50% drop in combustibility extensively in their well respected book.
              Since I don't happen to have a copy, would you care to provide a citation in context? Just saying that they "use it" in the book somewhere isn't very helpful.
              "Nemo Plus Voluptatis Quam Nos Habant"
              sigpic
              The Code is more what you'd call "guidelines" than actual rules.

              Comment


              • #52
                Originally posted by DeputyMarshal View Post
                Since I don't happen to have a copy, would you care to provide a citation in context? Just saying that they "use it" in the book somewhere isn't very helpful.
                Provide a citation in context?

                I already have. Multiple times.
                Last edited by J.Beck; 12-30-2010, 11:18 PM.
                Cognition before Ignition

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                • #53
                  [QUOTE=DeputyMarshal;1234494]
                  I'm not disputing the value of the technique in attached exposures -- just detached ones.
                  QUOTE]

                  It makes no difference - attached or detached.

                  The same concepts hold true.
                  Cognition before Ignition

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                  • #54
                    Originally posted by J.Beck View Post
                    I have no idea what you are talking about in your second paragraph. So I will address the first one only.
                    Sorry, slight attempt at levity at your expense. Clearly you've provided enough relevant information on the topic that we (certainly I) don't beleive you're a crack-pot or an explorer.

                    Originally posted by J.Beck View Post
                    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.
                    Ah, if I only had the time to be fired up (pun intended) about the subject. So far, traditional methods have worked well for us. Our weak attempt at PPA in the late 90's made us restrict it to an after knockdown tool. Clearly we were not fully trained well enough, though some key concepts of that day seem to be questionable now.

                    Much like the any religion, I don't care to prove it's wrong, but would prefer it proven correct to me. What we use works and has years and years of experience nationwide to back it. Will we move forward and adapt newer tactics? Sure, it's a matter of time and proof that to do so is truly worthwhile.

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                    • #55
                      Originally posted by J.Beck View Post
                      Provide a citation in context?

                      I already have. Multiple times.
                      Erm... No, you haven't. I'm looking for a specific citation and quote in context using CPS from the structural firefighting book you mentioned. I assume you have access to a copy since you referenced it.

                      Or an actual citation and quoted application of your assertion that combustibility doubles with every 18 degrees. (Which I still don't believe is entirely accurate. It sounds like a mis-application of a thermodynamic maxim about chemical reactions -- not "combustibility.")
                      "Nemo Plus Voluptatis Quam Nos Habant"
                      sigpic
                      The Code is more what you'd call "guidelines" than actual rules.

                      Comment


                      • #56
                        Originally posted by J.Beck View Post
                        It makes no difference - attached or detached.

                        The same concepts hold true.
                        I beg to differ on the basis that the "same concepts" aren't really relevant to both attached and detached exposures unless the "detachment" is so minimal that they might as well be considered "attached" anyway.
                        "Nemo Plus Voluptatis Quam Nos Habant"
                        sigpic
                        The Code is more what you'd call "guidelines" than actual rules.

                        Comment


                        • #57
                          Originally posted by DeputyMarshal View Post
                          I beg to differ on the basis that the "same concepts" aren't really relevant to both attached and detached exposures unless the "detachment" is so minimal that they might as well be considered "attached" anyway.
                          Beg to differ?

                          Ok

                          If you can't understand how fire reacts to differing pressures (negative, positive and neutral) then I can't help you.
                          Last edited by J.Beck; 12-31-2010, 10:42 AM.
                          Cognition before Ignition

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                          • #58
                            Originally posted by DeputyMarshal View Post
                            Erm... No, you haven't. I'm looking for a specific citation and quote in context using CPS from the structural firefighting book you mentioned. I assume you have access to a copy since you referenced it.

                            Or an actual citation and quoted application of your assertion that combustibility doubles with every 18 degrees. (Which I still don't believe is entirely accurate. It sounds like a mis-application of a thermodynamic maxim about chemical reactions -- not "combustibility.")
                            Don't believe that I am using that specific information in context?

                            You seem to be fairly interested in the subject. Or at least interested enough to try and prove it wrong..

                            Don't rely on me 100% for your PPA/PPV knowledge. Buy some books. Do a google search, etc.

                            All of my information is coming directly from NIST, UL, simple science principles, numerous live burns and multiple text books/trade journals.

                            EDIT: please don't twist what I said...what I stated was, "for every decrease of 18 degrees the speed of the chemical reaction leading to combustibility decreases 50%" not, "combustibility doubles with every 18 degrees".

                            Totally different.
                            Last edited by J.Beck; 12-31-2010, 10:45 AM.
                            Cognition before Ignition

                            Comment


                            • #59
                              Originally posted by J.Beck View Post
                              If you can't understand how fire reacts to differing pressures (negative, positive and neutral) then I can't help you.
                              I understand it just fine. I might not be quite done with my MS in fire protection engineering but I think I' ve got that particular bit down pat. :P

                              What I'm trying to understand how you are applying it to detached exposures and you're being annoyingly evasive about responding to direct questions. Unless the detached exposure is very close (effectively attached) and/or the smoke and fire gas velocities exiting the fire building are very high, pressurizing the detached exposure is doing a lot of work for very little benefit because the primary means of heat transfer is going to be radiation -- not smoke and flame directly entering unprotected openings.
                              "Nemo Plus Voluptatis Quam Nos Habant"
                              sigpic
                              The Code is more what you'd call "guidelines" than actual rules.

                              Comment


                              • #60
                                Originally posted by DeputyMarshal View Post
                                I understand it just fine. I might not be quite done with my MS in fire protection engineering but I think I' ve got that particular bit down pat. :P

                                What I'm trying to understand how you are applying it to detached exposures and you're being annoyingly evasive about responding to direct questions. Unless the detached exposure is very close (effectively attached) and/or the smoke and fire gas velocities exiting the fire building are very high, pressurizing the detached exposure is doing a lot of work for very little benefit because the primary means of heat transfer is going to be radiation -- not smoke and flame directly entering unprotected openings.
                                "Annoyingly evasive"

                                Interesting.

                                Ok, let me ask you a few things; how is pressurizing an un-attached structure a lot of work? What follows radiant heat exposure?
                                Cognition before Ignition

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