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nozzle selection in Flashover conditions

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  • #16
    Hey Guys - firstly we need to define the term 'flashover'....and that isn't as straightforward as it seems - http://www.firetactics.com/FLASHOVER.htm
    In simple terms a flashover is a heat-induced form of 'rapid fire progress' (NFPA) however, the transition is so closely linked with the phenomena of 'backdraft' that firefighters are often (usually) unable to define between the two.

    There are many valid statements already on this thread....and some not so valid! Lets try and keep to the original poster's questions without entering into a standard smooth-bore v fog debate!

    Smooth-bore .v. combination nozzle to (a) test the atmosphere for flashover and (b) use in flashover conditions?

    In (a) you can use either to probe 'test' the heat in the overhead. If you cannot see or feel the heat in the overhead it is a good tactic to place a brief 'burst' (small amount of water) up there. If the overhead is super-heated or hiding a rollover above your heads then you will HEAR the sizzle and pop of the water as it converts to steam.

    In (b) it has been proven in many many research projects that water applied in fog patterns will cool the overhead far more effectively than a straight stream of smooth-bore. If the fog pattern is 'pulsed' in controlled 'spurts' then there will be NO over-pressure or steam engulfing the nozzle crew and NO upsetting of the thermal balance http://www.firetactics.com/THERMAL%20BALANCE.htm

    However, the TWO main points are this -

    1. If you are in the fire compartment itself and it is not too large then flowing water of either stream (fog or smooth) will most likely prevent a heat-induced flashover.

    2. Any venting action initiated either by firefighters or naturally occuring MAY cause a heat induced flashover.....be aware of that fact!

    Finally, the 'pulsing' of fog patterns into super-heated fire gas formations in the overhead are FAR MORE LIKELY to 'inert' these dangerous gas layers than any smooth-bore stream, greatly reducing the potential for backdraft or smoke explosions.

    and Blacksheep........I admire your efforts at trying out 'pulsing' tactics but would suggest you don't throw out these techniques too early! Many firefighters in the USA have undertaken extensive and in-depth research of the fog pulsing tactics and approved this method, particularly for flashover control. http://www.firetactics.com/AUSTIN-TEXAS.htm and http://www.firetactics.com/US-NAVY.htm are a couple of examples.

    Stay safe
    Euro Firefighter 2008 - Strategy & Tactics from the World's Firegrounds


    • #17
      Originally posted by mongofire_99:
      To my limited knowledge, there has never been a firefighter injured in a flashover when any nozzle was being properly operated.
      And for anyone who questions that, there are two conditions here:

      1) Being operated (flowing water)
      2) Operated Properly (putting the water in the right place, either on the base of the fire, or appropriately in the overhead area)

      So the nozzle must be on and being operated properly.

      I would agree with this general proposition, unfortunately, many burn injuries occur while entering and seeking fire, etc., prior to operation or prior to full operation.

      [ 11-15-2001: Message edited by: no_name_FF ]
      The above is MY OPINION only and not that of anyone else. I am not representing any organization in making a post here!!!!


      • #18
        Yep, rapid fire spread, that was it all right. I haven't thrown out the idea of "pulsing", at least yet. We have a flashover simulator down here that I have played around with. The flashover conditions can be controlled by the pulsing as you say, but the nozzle that is used flows only 30gpm, and it works best on straight steam to control the fire w/o bringing the steam down on everyone. One advantage that I (we) have during this is the use of a thermal imager, which allows us to be much more precise in the control. But I really believe in the real world that a smooth bore nozzle stream bounced off the ceiling (pulsed) would be just as good. The fire we have is under extremely controlled condions that are known before hand, reality is usually not anything close to that.


        • #19
          So the nozzle must be on and being operated properly.

          I would agree with this general proposition, unfortunately, many burn injuries occur while entering and seeking fire, etc., prior to operation or prior to full operation.

          I agree with you as well.

          But for the sake of arguement we can hardly blame this on a nozzle.
          It's only my opinion. I do not speak for any group or organization I belong to or associate with or people I know - especially my employer. If you like it, we can share it, you don't have to give me credit. If you don't, we are allowed to disagree too (but be ready to be challenged, you may be on to something I'm not). That's what makes America great!


          • #20
            no name FF raises a valid point in terms of firefighter injuries caused through 'flashover' and it is true that most inj's do involve firefighters working without a nozzle in search and rescue ops. This is an unfortunate situation but in most cases there are OTHER factors involved that caused the 'flashover' to occur, either through actions taken (or actions not taken) by firefighters. Perhaps a vent opening was made that fed oxygen to the fire; or there was no line or crew assigned to fire control at the outset due to manpower problems on the initial attendance. Perhaps the searching crew COULD have worked with a 1 1/2 inch protective line.....? This is a tactical problem and not a nozzle problem as Mongo states.

            Blacksheep makes some interesting points that I would like to address -

            Does the nozzle used have any higher flow settings? Most nozzles will provide a flow selector to enable higher flows when required. If so, yes....the lower flow setting of 30 gpm is often used with a pulsing FOG action utilising around a 35 degree cone spread in the simulators to cool the heat in the overhead, or even to extinguish burning gases. I am surprised on your comments because we have been using thermal imagers fitted with pyrometers for some years in the simulator to demonstrate how a fog pattern is MORE effective than a pulsed straight stream at taking the heat out of the overhead. This is also measured via thermo-couples permanently sited in the simulators and the effectiveness of differing stream applications is clear to see. I would mention that water droplets from the fog pattern should be small to achieve good effect and often a spinning toothed ring is able to break them down further although this is not an essential feature. Larger droplets tend to pass right through the gases with minimal effect before striking the steel walls of the container - and creating STEAM! Smaller droplets turn to steam in the gases but the cooling effect SHRINKS the gas layers and absorbs any steam - but this takes training and experience to gain such control, although many firefighters can grasp the basics in 15 minutes!

            Real world - we have been using these techniques in the real world for a long time, personaly since 1984......they DEFINITELY do work there too.

            1. Pulsing fog to cool the overhead and prevent 'flashover'.

            2. Pulsing fog to 'inert' dangerous formations of fire gases that could ignite in a 'backdraft' or 'smoke explosion'.

            3. Pulsing fog to extinguish gas layers that are burning off in the overhead.

            4. Pulsing fog to knock-back a dangerous 'rollover' effect at the ceiling.

            BUT - 5. Direct attack in straight-stream form to extinguish flames at the fire's source.......once you've found it.

            That's why a combination nozzle is required. Its the most versatile tool a firefighter can take into a compartment (room) fire for when he has been taught to assess each risk - read the conditions based on fire behavior, select the correct flow and cone pattern he can then apply the most effective option for each scenario......and NO, it does NOT take too long to change between options. Trained firefighters ARE able to THINK and ACT with speed and select the right option instantly. I like TFT nozzles because they are the only ones I have seen that allow rapid changes of the bumper (fog to straight-stream) with an effective and easy to use selecta-flow ring. However, there may be others around.

            Firefighters who constantly suggest that one form of stream or nozzle is best are not thinking laterally - they CAN and SHOULD be trained to accept that different conditions demand an adjustment of the stream to achieve the safest and most effective options.

            Euro Firefighter 2008 - Strategy & Tactics from the World's Firegrounds


            • #21
              The nozzle that we use does not have a gpm setting, it flows only 30gpm(for the safety freaks out there we do have backup nozzles) and I can see where there are some benefits to using a fog to cool the overhead, and it's nice that you have access to such a high tech simulator, God bless you I wish we all had them. However, more often than not I've seen fogs mis-used and brought the atmoshere down on the occupants, pushed the fire into uninvolved areas,on & on. If you had all of the information, thermal couples, proper venting, proper gpm etc. monitoring all of them at the same time, you could probably pull it off. But when the there are dynamic changes occuring every second it will be a lot harder. In our case back 16 years ago we tried to go by the book as far as the interior attack went and got screwed. Now I realize this would not be considerred "proper nozzle operation" in the strictest terms and is therefore open to speculation. But when making an interior attack in an occupied structureI preffer not to make steam, and I contend that the overhead can be controlled by a straight bore nozzle as well as a fog without the unintended problems. There are other factors gpm, reaction force being some, that I won't debate here, that play into that decision. I would like you to consider something else, if you open a fog say 30 degrees, won't it also tend to bring in fresher/cooler air from the point of entry and in some cases, couldn't that even add to the dynamics of the situation? Lastly, I have to disagree on your choice of nozzles, I would pull a manual adjustable fog before using a combination nozzle.

              [ 11-17-2001: Message edited by: BLACKSHEEP-1 ]


              • #22
                Sure thing Blacksheep - a 30gpm nozzle has limitations, even in a simulator burn, and the whole point of simulators is that you should be training with the nozzles you are using (or are planning to use) in the 'real' world. In any training burn we always have back-up nozzles anyway, whatever the initial flow is.

                Your point on the misuse of fog is acknowledged Its a training matter though.

                'Real' fire and smoke dynamics ARE totally different but our training is advancing into multi-compartment and purpose-built structural situations so that firefighters can learn even more about how fire gases behave. There are also certain conditions that every now and then present themselves on the fireground that are ideally suited to these techniques - I remember one (as an example) where a reservoir of burning fire gases had accumulated at the top of a stairshaft and the discharge of two quick pulses (bursts) of a 35 degree fog killed the whole thing - no steam - no water damage - total visibility maintained - no water damage - good effects all around. Another time I was trying to make a hallway that was filled with fuel-rich superheated fire gases rolling down as we crawled in. A few brief pulsations as we advanced down the hall took the heat out of the overhead, maintained visibility at lower level, no steam and I am CERTAIN - prevented the hallway from flashing on us. This style of attack IS NOT for every fire but you get to know WHEN it will achieve GREAT effects!

                In answer to your question - yes, normally fog streams do attract additional air into the room behind the stream - moreso than a straight-stream/smooth-bore. But 'pulsing' applications are not associated with this effect as the bursts are so brief....

                What is a 'manual adjustable fog' nozzle? I understand that to be the same as a combination nozzle that provides both widening fog patterns and narrowed straight-streams?

                Stay safe.....

                [ 11-17-2001: Message edited by: Paul Grimwood ]
                Euro Firefighter 2008 - Strategy & Tactics from the World's Firegrounds


                • #23
                  This is what some of us refer to in order to differentiate between a combination nozzle that is not gpm adjustable except possibly by pressure (a TFT would probably be a good example of this),and a gpm adjustable nozzle. There's also the old PDQ nozzles but I haven't seen one of those for awhile. While you may like a fog for more adjustability, I like a manual nozzle for more control. That's a gross oversimplification and could lead to a whole new series of arguments. Your example of the indirect attack at the top of a stairwell is a good one, in that case I might wish to do the same thing. But I would also say that is an abstract to prove your point. One other thing, what if there was a victim near the top of that stairwell, they just went from bad to worse.You also mention multiple compartment fires, this is exactly what Layman was talking about when he wrote the book on fogs back in the 40's and 50's. But he never advocated the use of fogs in an occupied structure. One item you mentioned is the ring that disperses the water particles to even finer drops, I do agree with you on that, To me that spinning ring is a hallmark of a great fog nozzle, however, I also think it hurts the straight stream characteristics. I had to bail out of this for a call and I came back an edited it so I'm not trying to swerve you if you didn't read all of it.

                  [ 11-17-2001: Message edited by: BLACKSHEEP-1 ]


                  • #24
                    OK but I am not sure if your terminology is universal, even in USA? TFTs come in several formats - AUTOMATIC which ARE manually adjustable in terms of flow; SELECTABLE FLOW which are also adjustable and FIXED FLOW which require adjustments away from the nozzle to alter flow. However, ALL of these are termed COMBINATION nozzles in that they provide both fog patterns and straight stream options?

                    Your references to Lloyd Layman and INDIRECT fog applications are not at all applicable to 3D pulsing tactics. The notion of PULSING a fog pattern is based upon an intention to AVOID excessive water striking hot walls and ceilings - it is exactly the OPPOSITE of Layman's techniques. These are 'new-wave' techniques....... http://www.firetactics.com/FIREENGINEERING-1.htm

                    Finally, any spinning 'tooth' ring fitted to a nozzle should have no effect on the straight stream as it does not come into play until a widening fog cone is utilised.

                    Take care bro...
                    Euro Firefighter 2008 - Strategy & Tactics from the World's Firegrounds


                    • #25
                      The idea of introducing just enough water into the atmosphere and in the right place to control flashover is interesting, I especially noted the part that stated a solid bore could be used with equal results by using a"z" pattern. Still I have to wonder if such an exact science is applicable to real world firefighing. One other concern I have is that in the shipboard scenario is construction. Heat transfer in a steel box is a lot different than a single family dwelling, or a hi-rise ,etc. What if you took something like a navy ap nozzle with the foam attachment (and ideally the attachment would have a hi-pressure fog tip) an use the tube to prevent vaporization of the stream until it was at the correct position in the atmosphere? This is a little esoteric, but it seems you have all of the toys available to you, so why don't you try it?


                      • #26
                        'is such an exact science is applicable to real world firefighing'? Well these techniques were introduced by scientists and developed by firefighters firstly in training scenarios and then in the real world. They are standard procedure in several countries including throughout the entire UK - and there is no way our national training bodies would have accepted this for the 'real-world' without substantial evidence.

                        The techniques were adopted for 'steel-structured' ships partly because the water requirements are low - but also due to the fact that the methods represent the most effective way to PREVENT (not control) flashover conditions and deal with burning gas formations. Again - effective applications avoid excessive surface contact by water so the wall and ceiling linings are somewhat secondary to the real aim which is -
                        evaporation of water droplets in the fire gases themselves.....

                        We have tried all sorts of fog tips and applications with great success but 'real-world' firefighting dictates that you will probably need a straight stream at some stage of the fire-fight. Hence the view that combination fog/straight stream nozzles are the most versatile and suitable for general compartment firefighting - more options for varying conditions.

                        In 1984 I was a smooth-bore addict! Now, after a further 17 years of studying, research and 'real-world' use I am convinced that these 'pulsing-fog' techniques are effective in flashover control (meaning prevention). But they are not for every fire and sometimes the high-flow and penetration from a straight-stream provide the best option.

                        The use of indirect (Layman) fog tactics should be reserved for compartments demonstrating and bordering on backdraft conditions where a clear gravity current http://www.firetactics.com/GRAVITY-CURRENTS.htm exists and such an application should be discharged from the exterior or in a defensive manner.
                        Euro Firefighter 2008 - Strategy & Tactics from the World's Firegrounds


                        • #27
                          Maybe that was poorly stated, let me give you two examples. about 24 years ago the fire service was all pumped up over hi pressure fogs, brilliant idea, extremely small amount of water droplets put out lots of fire. They no longer exist except in very specialized applications. About 15 years ago it was how sound waves effect fire, wouldn't it be great, a smoke alarm that could act as a suppression device without water damage, potential yes, will it happen well.... Now I like your idea (it's been around so maybe it's not YOUR idea) but as I see it and according to the web page you suggeted, this can be accomplished with a smooth bore, and if you add in some other factors like reaction force, gpm etc I still do not see the advantage of the fog in this case, Now maybe I'm a hard sell(or hardheaded) but I was in a flashover, I used this pulsing technique, or at least something like it and I had a fog nozzle. Now I like smoothbores. I would expect to hear something from mongofire on this shortly, I know he's out there somewhere......


                          • #28
                            My article went like this.........

                            'There are many ill-informed arguments mounted against the tactical use of three-dimensional water-fog, for example -

                            The stream from a smooth-bore nozzle can be used just as effectively to 'cool' gases in the overhead by utilising a 'Z' pattern. It has been scientifically proven in several independent research studies that fine water droplets WILL cool gases in the overhead far more effectively than a straight stream application. The US Navy tests clearly demonstrated this fact under strict scientific monitoring'.

                            I am not proposing the Z pattern from a smooth-bore nozzle but others, in the past, have! I pointed out that (and argued against), whilst it might work in the case of a HEAT induced 'flashover it is NOT as effective (not for debate ) as water droplets from a 'pulsed' application. If you take a hallway transporting layers of fuel-rich gases (in smoke) from the fire room towards the entry point the smooth bore CANNOT 'inert' these dangerous gases and prevent an ignition (smoke explosion or backdraft) as effectively as fine water droplets can.......no way!

                            If you use a Z pattern SB to tackle a reservoir of burning fire gases (as discussed previously - at the top of the stairwell) you will destroy thermal balance more than if you used 'pulsed' water droplets and reduce visibility drastically.

                            There are so many advantages of applying water droplets in 'pulsed' fashion and in each case, it has been proven both scientifically and practically (real world) that these methods are far more effective than SB or SS methods - for the purpose they are designed.

                            These are techniques introduced by the Swedish Fire Service, developed further in the UK and Australia and now used in many countries and currently gaining popularity in the USA.
                            Euro Firefighter 2008 - Strategy & Tactics from the World's Firegrounds


                            • #29
                              You seem a little closed minded on this subject (not for debate?) I watched a movie made by Fornell that showed guys "pushing" fire down a hall and back into the fire room, then extinguishing it. They did this without unduly disturbing the thermal balance. Now this 3d attack looks to me a lot like a combination attack only with less gpm being introduced to the atmosphere, it seems the trick is to keep the flashover from happening w/o disturbing thermal balance, we've been doing on this for years.


                              • #30
                                Not for debate?......What is the purpose of debating something that has been proven in many independant scientific research projects in several countries? These scientific statements have further been confirmed by 'real-world' firefighters internationally. How can you debate something that certain? I have been debating this topic for 17 years and I have yet to find someone who will frame a debate beyond personal opinions or experience that is flawed in some way. Show me some REAL EVIDENCE beyond your own opinions that will verify a smooth-bore stream will cool the overhead WITH BETTER EFFECTS HAN A 'PULSED' FOG PATTERN......show me this evidence...cos I have provided you with a ton of evidence that is beyond debate. If 100 percent of scientists and universities and firefighters that have researched this topic over 19 years all come to the SAME conclusion - then THAT is beyond debate.......or perhaps the world IS flat after all

                                COMBINATION ATTACK? You are so far off the track Blacksheep I am not sure you understand what the combination attack is all about! If you are comparing it to 3D fog applications then our own debate is failing! Maybe it's me....perhaps I don'y have the ability to put this across to you.......or perhaps it's you.

                                'Combination Attack' - The need to bring together two things - 'the right amount of water and the right way to apply this water', only.....this was referring to 'indirect' attacks and NOT 3D offensive applications. All references to COMBINATION ATTACK SUGGEST THE WATER SHOULD 'STRIKE AS MUCH OF THE PERIMETER SURFACES, WALLS AND CEILING, AS POSSIBLE, to create a steam blanket'.....NOT 3D fog tactics AT ALL!
                                Euro Firefighter 2008 - Strategy & Tactics from the World's Firegrounds


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