Water-fog in the Overhead?

[Paul Grimwood]

Chief Vince Dunn is one......David Fornell is another....in their textbooks on firefighting tactics, who strongly oppose putting water up into the overhead to cool the gases. 'just causes a lot of unnecessary steam' is the consensus. However, reading the forums here there are a whole lot of views on this method or style of application. My stand is in strong in support of placing small amounts of water-fog into the overhead to cool the gases and inert the flammability of the layers. Too much water and you get masses of steam. But if applied in short bursts (pulses) the fine water droplets will cause the superheated fire gases to contract, creating a negative pressure and NO steam balloon. What's your view? What's your experiences on this?

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[Truckie from Missouri]

I'm in favor of cooling the hot gases. I do it myself, and have learned the hard way that SHORT bursts are all that is needed. My first fire (many moons ago) I thought I knew better than I was instructed, thinking that if a short burst works, well, a long burst will be better. WE'll see, won't we.

It is better, ASSuming you want to lobsterfy yourself and your fellow crew members. Makes for some excellent (not) attitude enhancement in regards to your skills, too.

I am, to an extent, in agreement with Chief Dunn and Captain Fornell, that it will cause steam. If done improperly. I have also been told that hitting the gases will cause more water damage. Well, my theory here is if it don't get wet, it will most likely burn. Water damage is the least of my concerns during initial attack. When the fire is knocked down, then yes, property conservation comes into play. BIG PR tool here. However I feel that life safety takes a bigger role during initial attack ops (attack, ventilation, search/rescue, etc.) Grandma would most likely prefer that we save the grandkids and limit fire spread and then try to save the heirlooms (equally important, but not as high a priority).

VENTILATION is the key here. Good ventilation early will dramatically reduce these effects. I am a firm believer in "Vent early, vent often." As soon as the attack team is ready, start venting. Pop a window. Open the roof. set the fan. However you do it is not important. JUST DO IT!

Ok, enough rambling on tangents here. If cooling the gases makes it safer and easier to advance on the fire, DO IT! Train to do it properly.

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Proud Member of IAFF Local 3133!

Stay safe.
Ken

[stone35]

I believe that the two gents are correct in that turning your hose open into the superheated atmosphere will cause lots of steam, and a great way to find your fireboots filled with grease and other fine firehouse products. On the other-hand, short bursts have been shown, studied extensively in European countries, used by myself and my fellow firemen, and it truly helps cool and dissipate that thick black smoke that tends to ignite and blow you out the backdoor.

Before I was a fireman I was watching the Discovery Channel and one show was dedicated to innovative ideas in firesafety. One was the use of short bursts of water to cool and clear the particle/smoke from the ceiling. It was amazing to see the difference. It was like a magnet being dragged through a pile of flour and metal shavings.

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Stone35

[Bob Snyder]

I'm with Ken (Truckie from MO) on this. I do this whenever conditions call for it. I don't have anything else to add because he's pretty much covered it.


[This message has been edited by Bob Snyder (edited August 06, 1999).]

[T.D / 1122]

I too am with Ken on this one! I couldn't have said it better myself!

[CFD SQURT81]

Solid stream nozzles + Indirect attack above fire= Large water droplets to extinguish fire. Steam will only burn you, disrupt the thermal balance, and really is ineffective unless the steam has no place to escape... and we should be venting before we are extinguishing... unless we like to send our brothers in to baste.

Steams efficiency is in inverse proportion your amount of ventilation... dissipating quickly through these openings, it is only replaced by air, and as air replaces the steam, hot fuel sources reignite, thus defeating our purpose. Now we're burned up, can't see, and the fire is still burning! Even if you did knock down the fire, or darken up the room, You did not cool the fire enough to keep it from re-kindling. So really, what have we gained?


Fog is in no way as effective as a straight stream. Fine spray from a fog does cool the area above you, but that's not our goal... our goal is to cool the FUEL SOURCE to a point where it stops generating fuel gases.

Also, if a fog stream is directed towards a fire, you are pushing fresh air towards the fire also. While this may be good while trying to make a hallway or vent out a window, it is bad when the fire has no place to go. Imagine directing a fog stream into a room with no other opening excepg within. Where are the hot gases and fire going to go? Right over you, or through void spaces within the room, which can cause extension.

Another advantage of the solid stream is the fact that they require less pressure, and reach greater distances.

For those of you who use the stacked tips, You know what I mean. For those of you who have never had the pleasure, do yourself a favor. Short bursts, long bursts, whatever, they have limited benefits... benefits which are outweighed by the negatives.

Lets make it as best it can be for US!

[DD]

A question for CFD SQURT81.

Does your statement, "steam's efficiency is in inverse proportion to the amount of ventilation", mean a direct proportion or is it another ratio? Please reply with the formula that you use to arrive at the volume displaced by steam and its replacement with air.

I like solid bore tips, from handline through deck gun streams.

[Paul Grimwood]

When I posted this I thought I was going to get smashed by the smooth-bore brigade! As it is, so far, the 'foggies' have it 4 against 2!!

But lets take a close look at the comments so far.

Truckie - straight in there with a text-book answer....have you been to one of my classes Truck?!! and then Stone 35 backing Truckie up on the fog nozzle....and then in comes Bob Snyder with a most important comment....' using the short burst water fog techniques whenever conditions call for it'!

Hey - the important thing is, these three guys RECOGNISE there is a big difference between 'Indirect' water-fog and '3D(dimensional)' water fog applications, both in their use and in their objectives.

CFD Squirt 81 - describes the 'indirect' approach well and defines all the dangers and disadvantages of such an application. The discharge of water spray/'fog' onto hot surfaces became popular in the 1950s and unpopular in the 1960s!! Of course there's masses of unwanted steam in this situation and firefighters do get burned!

He says....'a fine spray from a fog does cool the area but that is NOT our goal - our goal is to cool the fuel source'! Hey, if we're talking about actual fire suppression, I agree! But what if........

Its hot and smokey, pushing in through thick smoke, two storey residence, no fire visible but plenty of hot black smoke! Can't see a damn thing - pushing on in....2 firefighters,
and an automatic nozzle on an inch and three quarter line....you can hear it, you can feel it....but damn you can't see a thing!! So, where do you put the water? What is your objective now? Find the fire....sure, but that might take a few minutes! whhhhoooaa!
Too late.......whhhhoooooommmppppp hhhhhhh!!
BACKDRAFT!! No warning....no signs like the text book tells us....you're toast!

Now if, you had been 'pulsing' the overhead with short bursts, suspending fine droplets of fog into the hot gases, pulsing the nozzle and not sweeping the spray pattern, maybe the backdraft would never have occurred. Maybe you cooled the gases sufficiently and inerted the overhead enough to prevent such rapid flame propagation. Maybe, you advanced on the fire, hit it with your straight stream and went home to your wife and kids!

So tell me CFD....if you are still uncertain,
just what benefits of the short burst technique are outweighed by the negatives? Please explain that statement? All the negatives you give are related to 'indirect' water-fog attack - none are applicable to 3D applications (which are not a means of fire suppression)! You seem to be saying tactical venting actions will diminish any water-fog application....YES! But only 'INDIRECT' applications. The use of 3D water-fog is complemented by tactical venting ops.

Hey DD....put your smooth-bore down....be open-minded about this and take a look at 'new' techniques and....as CFD says....

'lets make it as best we can for US'!!!

Please guys - take a look at my website!

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[CFD SQURT81]

VES. The truckies gotta get things opened up, so you can find the fire. You'll be crispened by a flashover, or worse a backdraft, if you have not vented properly. Cooling those gases and pushing in further may just get you in too deep, then what?

If the truckies aren't there yet, an alley apple through a window, etc. as your nob man is flaking his line, should help to start getting those gases out. ( Like the vent-point ignition we see at new openings) Thats the best way to cool those gases... get them out of there. I don't like the idea of a false sense of security that some say the fog provides.

Even if you have been able to cool the gases right above you, what about the gases still traveling towards you? Bottom line is you have to find the fuel souce and get water on it. Thats where the solid stream comes in. It can be directed above you to bounce off the ceiling, drop down plenty of water in large droplets ( which will still be water when they hit the ground) and we have great reach potential at lower pressures. ( Which means we can drag the hose easier, and those kinks don't have a dramatic effect ( most of the time )

Like I did say earlier, I think it (fog) can be advantageous making a hallway, etc... when you have a real good idea where the fire is, but to spray it above you for the sake of cooling whats above you, I think can only lead to trouble.

DD, I think the point I was trying to make is that once the steam dissipates, it has to be replaced by something, something being air. Steam will dissipate through any possible opening.

Keep it safe guys.

[Truckie from Missouri]

Actually, no, I haven't been to onw of your classes. I have, however, attended classes at the School of Hard Knocks.

I am more in fovor of using a solit tip nozzel. I like them because of the reduced reaction, they have a hellova punch, and, as a rule, the fire goes out NOW with them.

However, my department doesn't have very many solid tip handline nozzels, and I seriously doubt we'll get any for quite some time. So, I have made it my business to know how to use the automatics we have. They ain't bad, I just prefer the solid tips.

My main point is to train and know your equipment. (Part of knowing your equipment is knowing how to use it!)


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Proud Member of IAFF Local 3133!

Stay safe.
Ken

[Paul Grimwood]

CFD likes to VES! Hey, wasn't it Chief Dunn who proposed that concept in the first place?
Well I am in support of VES under the right circumstances, but to vent a window without having charged your initial hoseline - well you are just asking for rapid fire spread and
to anyone still inside the structure - bad luck!

Its a fact that temperatures may soar within the fire compartment once openings are made
and you need to get water on the fire pretty quick. You talk of 'vent-point' ignitions as being a good thing....I don't think so. Ok, its gases being released from the structure, but again, you may cause the fire to flash back into the compartment. Then, its the problem of gases coming at you......well if you apply the water-fog with correct cone pattern diameters and application angles then the zone coverage is most effective.

I know what you are saying CFD on the main stream technique but what if the fire isn't even in the same room as you - or maybe its on the floor below you (basement)! Hey, come on - what trouble will the 'short bursts' of fog cause for people still occupying the structure (including firefighters)?

Its'V' (after you have a charged line) then 'E' (with a charged line) and 'S' knowing your brothers are at least backing you up effectively. Get that water in there and cool those gases!

Hey guys......its still 4-2 to foggies!



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[Dalmation90]

'course I could really screw up the whole works and start a PPV attack used in conjunction with a 30 degree fog to push the whole works into the room of origin and out the window http://www.firehouse.com/interactive/boards/wink.gif

Won't work on every fire...but if you have a room with significant extension into the hallway or similiar scenario, let's not forget all our tools. No gases overhead 'cause the ppv and fog are pushing 'em out the window --> no need to cool the ceiling. Fire, smoke, steam, and water droplets all flying ahead of the attack team.

Matt

[CFD SQURT81]

Paul- You have same very strong arguments, but I'm still not convinced.

I'm still a firm believer in venting out the hot gases into the atmosphere as being the best way to keep them off of us. Conditions change so much for the better when you have the properly coordinated venting and extinguishing going on.

Occasionally, engine co's, or ladder co's get caught being first in with no help for a few minutes. Sometimes you have no other option but to vent before going in, and yes, they can make the fire conditions worsen while you're stretching up, but even though you have more fire, you have less problems finding it, and less problems being confronted with heavily banked down gases. Thats where proper, fast, and efficient knockdown from that tip come in to play. Lots of water, on the place you need it the most.

As for finding out where the fire is, if you're upstairs and the fire is in the basement, no matter what kind of tip you have... the only way the basement fire will go out is when the roof is sitting in it! Why stay upstairs cooling gases?

Lastly... if you do have a fire smoldering somewhere else, and it's hot as hell in there and you haven't found anything... what do you have to do to help find it? You have to start opening up. When I speak of Vent point ignition, I think the point I was trying to make is that those gases are so hot, that given just a little more oxygen, they're ready to light off. I don't want those gases in the same area I'm in if I don't need them there, I want them gone!
I'd rather be fighting a fire I can see.... not look for one thats waiting in the dark to jump me!

Lets make it the best it can be for us guys... stay safe.

[Aff]

PPV fans, vertical/horizontal ventilation, or even hydraulic ventilation are all excellent and probably the perferred method. But,(somehow there is always a but) when I was a shipboard firefighter, these options were not always available. -Cutting a vertical vent hole in an armored deck of an aircraft carrier can be time consuming http://www.firehouse.com/interactive/boards/smile.gif!- The only way you could advance was with cooling the gases and proceeding. Very quick, short bursts were critical as not to upset the thermal layer and put to much water on the steel surfaces, creating steam. I have used this sucessfully since, but not as much as the fore-mentioned ways. Another tool in the arsenal to to consider. Be Safe.
Mark

[Paul Grimwood]

AFF - Mark is right! The coastguard gave mention to what they described as the 'short water burst' technique , during tests sponsored by the Naval Sea Systems Command (NSSC)of the US Navy in 1990. It is another tool, as AFF so rightly says.

Hey guys.......in real terms, this isn't an either or situation. I am not suggesting a choice (smooth bore .v. fog) but rather an option.

Matt - that's one hell of a topic! PPV PLUS 3D water-fog applicatiobns in unison! We have been doing some research on this since 1993 but I would like to hear your experiences? It can work BUT there are also problems! What if the PPV outlet is too small to handle the outflow of gases? Where do they go? Where does the steam go? Its one hell of a burn as those gases ignite!! Be careful if your PPV is pushing in excess of 15,000 CFM with a 30 degree fog-cone behind it! That's where we found problems. But hey - tell me what you know on this topic!

CFD - I really do appreciate what you are saying in relation to venting those gases out and I support you. However, I still promote the view that - venting must not begin until you have your initial line charged. You tell me in a previous post (another thread) that sometimes we have to suck at the floor to get below the heat barrier - so why not 'pulse' some fog into the overhead as you do this?! Hey - I never suggested staying upstairs to cool gases when there's a basement fire to be fought! Its all in the approach to the fire. This is not a suppression option - this is purely a method of making the approach route safer! You must have been in there - when the smoke is hot and thick - and even attempts to ventilate don't relieve the conditions? THEN is the time to 'pulse' the overhead!

You talk of the smouldering fire that can't be found and how the truckies should 'open up' to release those superheated gases....I am with you again on that! But, why not 'pulse' the gases BEFORE releasing them so that when they hit the air outside, there is a fair amount of water droplets in them to prevent an ignition - and a 'flashback' into the compartment you are occupying?! Everything you say is ok CFD but, 3D fog is another tool - a way of making the gases safer to vent. I am not suggesting water-fog in suppression over straight stream attack but rather, just a way of making the approach route safer.

Hey guys....the eclipse in the UK was AWESOME today!! Just had to share that with you!

Stay safe brothers....look above you!



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[Dalmation90]

PPV...it's use for us is almost second nature now so I had to think of a good example. It's probably not good that it's second nature, because that will (and has) come back to bite us...but for most buildings in our area it works well.

Anyway, the clearest example I can think of was a fire this spring. We had a fire in a ranch house that was like the Energizer bunny...it just kept going and going. I arrived about 25 minutes into what was toned out as "A smell of smoke" at one of our town's fire commissioner's homes. Looking at flames 30' in the air I was wondering what the h*ll had gone wrong. But the fire was held to the screen porch in the rear and the rear bedroom. I think PPV played a critical role along with three (four?) handlines used to confine and extinguish the blaze. The fire was pushed out of one corner of the house instead of taking control of the whole thing -- and the build up was fast enough that the Chief arrived on scene to see light smoke rolling out the rear porch basement to having heavy smoke banked down to the floor of the living room when our first engine arrived a few minutes later.

Within 5 minutes of when I arrived, the fire was knocked down and extensive overhaul began. It was clear the fire originated in the basement of the rear screen porch, which fortunately was seperate from the main basement. But the fire fighters and Fire Marshal noticed some pink goo on the floor. Asked about it, the owner's eyes lit up wide as saucers...and the explanation of the intense fire was at hand -- he had stored 4 - 4x4x4 cubes of high density styrofoam in his basement planning to make a floating dock out of them.

I guess in hindsight one can only speculate what the potential would have been for the unburned-fuel laden smoke from Styrofoam if it wasn't being aggressively vented...I only saw the effects on the outside, and that was 30' of flames shooting out of the house!

One question for Paul, and I'm having a hard time phrasing it, but here it goes -- I can see masonry and steel acting as heat sinks and holding enough heat to make a lot of steam if your stream hits it. But I can't see Sheetrock being able to hold that much heat. Is there an observable difference?

Matt

[Paul Grimwood]

That's a very good question Matt. We have considered the use of water-fog in all sorts of construction types and they do vary across Europe. In the UK we often find the outer walls stripped of plaster in the fire compartment revealing bare brickwork - obviously a great heat sink! The inner walls and room partitions are generally sheetrock on timber frame although in older structures there is more substantial masonary and plaster wals. Yes, there is a noticeable difference between brick and sheetrock as heat sinks and obviously the steam expansion off an outer (brick) wall is spectacular!

However, don't forget, the discharge of water-fog into the overhead is 'pulsed' in rapid bursts. This is to ensure NO water reaches hot surfaces but vaporizes in the gases. Then - there is no noticeable effects at all!

The PPV situation was an 'ideal' experience (I am starting a separate thred!) - and I have seen those 30' flames you talk of!! Those gases really burn off don't they!!

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