02-09-2000, 09:14 AM #1FireAlanFirehouse.com Guest
"Pushing Fire" with a stream, theory and written studies
Apparently there are several opinions on pushing fire with a hose stream, I would like all opinions, but, need a source for any written study on this subject, which, preferably, includes heat sensors and such in the study.
02-09-2000, 02:46 PM #2STBURNEFirehouse.com Guest
There is much documented on the pushing effect of fog streams. All of the references below write about fog streams pushing fire:
Brannigan, Francis L. BUILDING CONSTRUCTION FOR THE FIRE SERVICE. 3rd ed. NFPA 1992. pg 97.
Clark, William. FIREFIGHTING PRINCIPLES AND PRACTICES. 2nd ed. PennWell 1990. pg. 38.
Fairfax County FD, VA. Extensive research in late 1980's.
Fornell, David. FIRE STREAM MANAGEMENT HANDBOOK. PennWell 1991. pg 93.
Fredericks, Andrew A. "Observations on the Engine Company." FIRE ENGINEERING. Vol. 151 April 1998. pg 93.
Grimwood, Paul. FOG ATTACK. FMJ Intl. 1992. pg. 74.
Gustin, Bill. "Fog Streams and PPV: Their Effects on Two Fires." FIRE ENGINEERING. Vol. 150 November 1997 pg. 49.
University of Illinois Fire Service Institute extensive research in late 1980's.
I hope this helps. Another good example is flammable gas fires. Most all Flammable Gas training utilizes a fog nozzle to "push" fire away from the valve, and the best way to mitigate hazmat vapors is to "push" (disperse) them with a fog nozzle.
[This message has been edited by STBURNE (edited February 09, 2000).]
02-09-2000, 03:41 PM #3S. CookFirehouse.com Guest
Not sure if it's mentioned in any of the references, but it should be noted that a fog nozzle adjusted to a straight stream will not push fire.
02-09-2000, 09:10 PM #4STBURNEFirehouse.com Guest
It is mentioned in Clark and Fornell. Because of entrained air that is in the fire stream (an inherent flaw of the fog nozzle), a fog on straight stream WILL push fire. It still pushes far less than a fog at 30-60 degrees. Next live burn you do, try both stream and nozzle types and compare the difference.
02-10-2000, 11:18 AM #5KEAFirehouse.com Guest
One factor the must be figured in with the "push" equation is the velocity of the stream. You will find that a straight stream at 100 psi exit veloccity will upset more of the thermal balance and increase the potential of "pushing" the fire, than will the same flow from a low pressure straight stream.
I will await the attacks on that statement and then quote where it came from. Although it is not my idea, it has proven to be the case in my personal experience.
Is it enough to worry about? I would say only if the second part of the equation is overlooked.
I beleive the second important factor (most important in my opinion)is the application rate. If you do not have enough to overcome the BTU exchange it will simply turn to steam, which means it expands, and then you end up with a fire that now has the potential of being "pushed".
As far as the entrained air in the fog, I think most will find that from a scientific standpoint, the small amount of air is not the real problem and possibly quite the opposite, from a scientific standpoint.
Please note my qualifying statement: "SCIENTIFIC STANDPOINT"
I say this beacuase of what is found in the 17th edition of NFPA Fire Protection Handbook under Theory of Fire Extinguishment, Page 1-73
"The flame temperature is so important because the rate of a key combustion reaction is very sensitive to temperature. A small decrease in temperature causes a disproportionately large decrease in the rate of this reaction , according to Arrhenius' Law".
"As an alternative to removing heat from the combusiton zone to slow the reactions, it is also possible to reduce the temperature of the flame by modyfying of the air which supplies the oxygen. Air contains 21 percent by volume of oxygen, the remainder being almost entirely the inert gas nitrogen. The nitrogen, which is drawn into the flame along with the oxygen, absorbs heat, with the result that the flame termerature is much lower than it would be in a fire burning in pure oxygen."
Just some food for thought
[This message has been edited by KEA (edited February 10, 2000).]
02-10-2000, 02:42 PM #6Lieutenant GonzoFirehouse.com Guest
In addition to theoretical and written studies that were posted on this thread, just interview any firefighter who has been on the the receiving end of an opposing hose stream or had a fire stream shot into a ventilation hole. The reply will no doubt be laced with obscenities, but it is the reality behind the theory.
Take care and be safe...Lt. Gonzo
02-10-2000, 02:46 PM #7FireAlanFirehouse.com Guest
Thanks to all for your thoughts, experiences and research. I have an ongoing "discussion" with fellow firefighters on the benefit of getting a solid, or, straight stream into operation as soon as possible without the time lag of forcing our way around to the unburned side. Let's face it, the sooner water is applied, the faster all the problems diminish, I certainly do understand that a certain amount of heat and smoke will get pushed, but, the benefit of a faster knockdown is far greater to those people who are already in peril, ventilation and heat reduction are effected sooner for a more rapid rescue.
But, I am still looking for a live burn study of all the factors concerning the application of streams, please keep your posts coming, I enjoy them all!
02-10-2000, 04:49 PM #8benson911Firehouse.com Guest
Approaching a fire from the unburnt side is appropriate and conserves property. But, if life safety is an issue, the stairs, or the occupant's egress route must be protected!
Every fire is different, so a hard rule of attacking a fire from the unburnt side in an interior position is inappropriate. Most fires shoud be attacked this way, but situations may bring about a need for exterior stream application or attack from other than the unburnt side. If the fire is venting from a window directly below the window an occupant is hanging out of, a straight stream into that room may knock the fire down enough to allow an exterior window rescue, or it may push the growing fire towards the occupant. Either way, the FF's can't save someone they can't reach.
Size Up is CRITICAL! View the whole scene, try to picture the layout of the interior, attack the fire in the most efficient and safe manner possible, given the circumstances. Sometimes a fog stream is needed, sometimes a solid stream, sometimes a straight stream from a combination nozzle. Use 'em all, but use the most appropriate stream for the situation.
02-10-2000, 07:41 PM #9S. CookFirehouse.com Guest
Tried both nozzles smooth bore and fog on straight, witnessed no noticable push.
Another test - hang a piece of ribbon from a swingset or something, shoot both streams (1 at a time) beside it or under it, close but not hitting it. Neither one should move the ribbon (unless water droplets hit it).
I'm going to test cfm of air movement along the stream when I do nozzle tests next month. Right now the plan is to do test at the nzzle and 1' down stream. Any other suggestions on theis?
02-10-2000, 09:05 PM #10Truck 2Firehouse.com Guest
Don't forget you need to get the water on the seat of the fire! You can't put out smoke! Placing fire streams into ceilings area and messing up the thermal bounce especialy fog streams will cause unnecessary steam burns to the firefighters advancing the line and can steam to death any victims still in the building!
02-10-2000, 10:50 PM #11DDFirehouse.com Guest
Lt. Gonzo is absotively correct, as Tigger would say. I have tried it and didn't like it. Luckily our 2-1/2 won the pushing battle and kept the hose crew from getting fried. The language also got very hot, very quickly.
02-11-2000, 01:46 PM #12SmurphFirehouse.com Guest
How does the Vindicator nozzle fit into this question??? It is a straight stream, but not a smooth bore. The vindicator by design pulls air with the water similar to a foam nozzle.
02-11-2000, 02:09 PM #13Lieutenant GonzoFirehouse.com Guest
Please don't let this thread become another battleground between Larry Stevens and Kirk Allen! While both of them are without a doubt knowledgeable, we want to learn from the forums and not bring corporate bashing and personality differences to the forums...if they want to do that, let them do battle on MTV's
Celebrity Deathmatch, Firehouse.com division!
Take care and be safe...Lt. Gonzo
02-11-2000, 02:57 PM #14KEAFirehouse.com Guest
SMURPH: At the request of the forum managers I will not be able to address your question regarding the Vindicator nozzle.
For the rest of the Forum members. Rest assured that the only argument that can arised form this topic will be a one sided one. I will not participate.
I will answer Smurphs question via e-mail.
Smurph, for the record, you are from Salem Illinois according to your profile. Salem has been using them for over 3 1/2 years. Have they discovered any problems related to the topic on this forum? Please not that the best source of info on your question will be your own people.
First Strike Technologies, Inc.
02-11-2000, 04:41 PM #15Bobby HaltonFirehouse.com Guest
Firealan, I am not sure you could get any better references than the ones listed in the above postings. I have found in my experience and in our departments training that the straight steam smooth bore nozzels were what I perfered for interior attack. However primarily due to my age, I do not go into structure fires any longer. I hope your organization is willing and open to suppling both types for their companies. Then the company officer (the guy/gal doing the work) can make the decision on scene. It seems we sometimes take an all or nothing approach when our common sense gene fails us. You have raised an interesting post I enjoy the responses, please continue. Stay low and be safe. Bobby Halton BTFG@prodigy.net
[This message has been edited by Bobby Halton (edited February 11, 2000).]
02-12-2000, 09:44 PM #16flyerFirehouse.com Guest
No doubt we must get water onto the base of the fire. However we must be aware that the unburnt fuel in the smoke layer can suddenly ignite when it reaches AIT. This can result in Rollover, Flashover, Backdraft or even Smoke Gas Explosion. It is vital to deal with the smoke to control the environment. Removal of the smoke via appropriate and well time ventilation is one method. It is also possible to inert (temporarily) the smoke layer via the skillful application of fog into the overpressure area (ceiling). OVER application WILL destroy the thermal balance and generate excessive steam. Careful application can actually maintain the thermal balance and if effected correctly can actually raise the neutral plane. This improves conditions for firefighters and entrapped occupants and aids in the location of victims and the seat of the fire. These techniques have been taught to the Swedish Fire Service since the mid 80's and it has gained wide spread acceptance in the UK and is now being taught in 3 states of Australia.
See Paul Grimwoods site at www.firetactics.com
In answer to the original question, fog nozzles can have a very powerful effect in pushing the fire. The firefighter must be aware of this. I have seen cases where this effect was used to advantage. I have also seen footage of Swedish Firefighters actually pushing the fire right out through the back door of a structure in seconds. Naturally size up and communications are essential here to ensure it is used at the appropriate time, and follow up is essential to prevent reignition.
02-12-2000, 11:11 PM #17LHSFirehouse.com Guest
<<unburnt fuel in the smoke layer can suddenly ignite when it reaches AIT. This can result in Rollover, Flashover, Backdraft or even Smoke Gas Explosion. >>
Another good reason to have a combination nozzle. You've got a smooth bore and a fog in the same nozzle and every stream inbetween.
02-13-2000, 05:19 AM #18Paul GrimwoodFirehouse.com Guest
There were some tests by University of Maryland (reported in my book Fog Attack) that produced data in relation to water-fog streams 'pushing' airflows ahead of the stream. However, the intention was to demonstrate the amount of 'smoke' that might be ejected from a window when using the 55-60 degree fog pattern to ventilate.
The amounts of air moved by the fog stream varied from 5,406 Cu.Ft.min at 60 gpm on a 1 1/2" line to 8,798 Cu.Ft.min at 250 gpm on a 2 1/2" line.
It was also noted that the results were variable amongst different nozzles.
I too can testify what it feels like to have smoke and heat 'pushed' in your direction!!
However, read Flyer's post carefully, because he is making the point that Water-Fog applications CAN be utilised effectively and safely WITHOUT 'pushing' the fire ahead of the stream. Its down to the application style - by PULSING the nozzle.
This technique is the MOST EFFECTIVE and SAFEST method of cooling superheated fire gases and 'inerting' flammable smoke there is. PULSE PULSE PULSE!!!
02-14-2000, 05:45 PM #19CFMJayFirehouse.com Guest
In have never written an article or book on a fog stream pushing a fire but I have been on the opposite end of several and very important lessons were learned by all. I do advocate protecting the stairwell for the occupants and attacking from the unburned side is tempting but the safety of all firefighters must be considered first.
02-16-2000, 08:04 PM #20flyerFirehouse.com Guest
The interesting thing about Paul Grimwood is that not only has he written a number of books and had a large number of papers published he has also spent a lot of time at the pointy end. And not as a Senior Officer, but as a firefighter!
Paul has served as a professional Firefighter for 26 years mostly in one of Londons busiest Stations. He has a long list of other achievements. And I am sure that he has been on the receiving end of more than one blast pushed along by a fog nozzle (as have I). It only goes to show how important it is to use the most appropraite tool in the CORRECT manner. Every type of nozzle has it application.
02-16-2000, 10:14 PM #21STBURNEFirehouse.com Guest
My opinion is to go with the smooth bore, this removes any chance of error and no one will have to be on the receiving end of the "push". Do not forget the victims! They are usually the ones on the receiving end of said "push" and don't have the benefit of protective gear and SCBA!
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