02-04-2001, 08:56 PM #1BrtengrFirehouse.com Guest
Thermal Balance questions w/ scenario!
So here's the deal. You are the officer on a nozzle team sent to find the fire in a light commercial structure (or large luxury residence). There is smoke pushing from every opening, but no visible flame from the outside. Being a creature of habit your 3-man nozzle team pulls a 200' 1-3/4" preconnect off the rig w/ an automatic nozzle and makes the front door. After you enter, within the interior of the building you encounter a large room 20'x20' w/ 12' ceilings (your lazer tape measure told you that at the doorway), this room is probably a work room (or large dining room in the residence). The point is it has a large fire load to fuel the full-involvement. What I am trying to get at is that the room is just large enough w/ enough fire that it is at the edge of your line's capabliliy. You are on a straight stream setting and you aren't making any headway. So what to you do?
A) Change the nozzle pattern to a fog setting between 30-40 degrees of spread and initiate a combination type attack (hit the ceiling, left-wall, floor, right-wall, ceiling)? This attack has the possibility of snubbing out the fire with the steam generated, upsetting the thermal balance, and cooking you too. Maybe an option.
B) Call for a bigger line and dig-in until it gets there, staying on your straight stream. This will probably keep you cooler and keep the thermal balance intact.
C) Go outside with your team and get a larger line and strech it in yourselves. This will give you time to cool down for a moment and tell the other guys what is in there. It also gives the fire time to build, so watch it when you go back in.
What I would like to know is if you upset the thermal balance and steam the joint with option A, but it doesn't work, how long will it take for things to straighten themselves out inside before you have to go in again and face doing it all over again. Short of venting the ceiling to roof and making things better, is it possible for the balance to recover? And things to be hospitible enough for entry again?
I know I am leaving a lot of information out, but assume that the structure is heavy timbers and its going to take a long time for collapse to be a problem. The jist of all this is I want to know if besides the steam problem, is upsetting the thermal balance a real problem? Can it restore itself if burning is allowed to continue? Oh, and I just thought of now if the balance is ruined at what point will it be impossible to vent the room because it cooled off enough that the gasses won't rise?
Just to show how possibly wrong I could be, I would have picked A and took my chances (while I called for a back-up line of course).
02-05-2001, 12:10 AM #2gicciFirehouse.com Guest
If I was in that situation this is what I would do. Once I realized that the 200' line was short I would have had my team back up to the entrance, then I would tell my wagon driver that I need a rack(100' 1 1/2", 2 1/2' reducer, and a pipe). I would then diconnect 50' from the rack and extend my line to the base of the fire, and go get it. As for a back up line the engine company that picks up my supply line would advance one behind my team according to SOP's.
As for the the thermal balance, while me and my team were extending our attack line the truck companies that are dispatched would be ensuring vertical and horizontal ventilation.
This is one possible solution and I am sure that there are many others.
02-05-2001, 12:53 AM #3BrtengrFirehouse.com Guest
I didn't mean that the line was too short. I mean that the GPM that the line is capable is not enough for the BTU's in the room. See if that changes your answers.
P.S. Thanks for taking the time to answer.
02-05-2001, 01:31 AM #4lumpy649Firehouse.com Guest
Good question, though it may be interpreted many different ways to many different people. What may work for Big-City Engine 37 may not work for Rural-Supplyville Engine 2.
In my area, the second and third engines (and even fourth and fifth-due in some cases) are usually no more than 4-5 minutes behind me. I have the luxury of having help right behind me should my plan fail. If my plan falls short, by the time I realize it and have made the decision to change the strategy, the second engine is pretty much right up my a** anyway, and I can call for a line of equal or larger size to be stretched while my line is at least slowing the spread of fire, and buying me a little time. Others may not have that help for a while, and obviously would have to choose between staying and trying to hold it or letting it go for a minute to stretch bigger line. Also, staffing comes into play- we generally have around 5 on an engine. That gives me three firefighters plus myself (I'm not afraid to get my white shirt dirty) to make the stretch... why not go in with a charged 1-3/4" line, and stretch the 2-1/2" dry at least to the front door, to be ready for the backup crew when the second-in arrives, or I send two out to go pull it in and have it charged? Typical? No... Creative? Yes... Risky? Could be... but that's the role of an officer- to weigh the risks against the benifits of an action. It's what I might consider doing. Hmmm... has anyone ever brought up the dry vs. charged entry argument up?
02-05-2001, 01:51 AM #5StaylowFirehouse.com Guest
I think you are wasting too much time worrying about the Thermal Balance. I personally am not a proponent of the fog pattern and the steam it produces. I wouldn't want to produce any steam. Particularly from a line that I know isn't putting out enough water to deal with the btu's that are in front of me. I see ventilation and getting water to the seat of the fire as the only viable means of controlling the conditions inside. If you do not have the water to deal with the btu's then you have to get a larger line or more lines to work in order to deal with what you have. Get your 2, 2.5, or 3 inch line to work, or use multiple 1.75 inch lines. But, until that roof gets open the engine crew is going to earn their pay. If you are not on the top floor then horizontally vent.
02-05-2001, 01:52 AM #6gicciFirehouse.com Guest
Well since the problem wasn't that the line was short it was that you just weren't doing anything with the straight stream attack; well since you are already in there and hopefully your truck crew is ventilating go ahead and try the fog pattern. If that doesn't work like lumpy649 said you could have the next in bring in a larger diameter hose. Another idea is if you are in an area where the next in is right there you could also utilize there hand line, that is if the room was big enough for both of you.
In my department the big thing is to put the fire out quickly, you don't want anyone else to get your fire, so if you have to disrupt the thermal balance that's what you do.
This could also mean one crew placing two attack lines in service in a very short period of time.
02-05-2001, 09:08 AM #7Halligan84Firehouse.com Guest
Since the average company probably flows 150 GPM or less with this hose/nozzle combination, howabout just asking for more water!.. 20x20 or 400FT2/3 =133 GPM using the NFA formula should be within the range of the 150 GPM stream, but maybe the fuel load and higher ceiling are making a fight of it. You can easily flow 200 GPM or more, making 400 square feet of fire pretty reasonable for the original crew with the original line.
02-06-2001, 01:01 AM #8FyredUpFirehouse.com Guest
This may seem petty to some of you, but you are using the term thermal balance incorrectly.
Thermal balance is when the temperature at the lowest point (floor) in an area is nearly the same as at the highest point (ceiling) in an area.
Thermal imbalance is when the majority of the heat, smoke and fire gasses have accumulated at the highest point (ceiling) in an area and the lowest point (floor) is substantially cooler.
What you don't want to do if you are in the immediate fire area is to disrupt the thermal imbalance and thereby bring the heat and smoke and fire gasses down on you.
The surest and quickest way to disrupt the thermal imbalance is to place too much water into the super heated atmosphere at the ceiling in the form of a fog stream. This type of fire attack is called an indirect attack and should NOT be undertaken if you are in the fire room or if there are possible survivable victims in the fire room. The circumstances where this type of attack works well is in a fairly tight room or area, especially if you can shut the door, with you on the outside of the room and let the steam do its work.
A direct attack uses either a straight stream or a very narrow fog from a fog nozzle or a stream from a smooth bore nozzle. The water is directed at the base of the fire and direct cooling of the burning material extinguishes the fire. Much less steam is developed and the thermal imbalance is usually mostly retained.
An combination attack is where a brief sweep of the ceiling for cooling of the atmosphere or flame extinguishment is followed by direct application of water to the base of the fire. Again, as long as the water application into the overhead is brief the thermal imbalance is maintained for the most part.
Now, on to your scenario. With the picture you paint a high flow line should have been the first choice. We use 2 inch hose with a 200 gpm at 75 psi break-a-part combination nozzle backed by a 1 1/4" slug tip (326 gpm at 50 psi). Or you could pull a 2 1/2" if that's what your FD uses or you could call for adequate engine pressure to flow 200-300 gpm through your auto nozzle. Just hang on because nozzle reaction becomes excessive.
I hope this is helpful.
Take care and stay safe,
02-07-2001, 01:56 AM #9lumpy649Firehouse.com Guest
Fyredup- you already know how much I respect you... preach it, brother!
02-07-2001, 10:31 AM #10SafeTrainFirehouse.com Guest
Some really great info from FyredUp! Pay heed. Personally, I would like to add some ventilation to the recipe. It's really hard to have all that heat and smoke crash down on you if it has already blown out the vent.
As for Gicci, please don't take this as a personal attack, as it is only intended as constructive criticism (I never claim to know it all, by any means). I know you guys are not the only ones with this mind set, but not wanting anyone else to get your fire is an egotistical, sophomoric, and unsafe operating method. It places pride and ego ahead of all else. On the fireground, we are supposed to operate as a team. That remains a constant whether you are working with your crew members, the next engine in, the mutual aid company, or even another agency. This is what is preached in all safety training. This is the purpose of I.C.S. Our mission is to safely mitigate the situation. We are here to fight the fire (or other emergency situation), not each other. I recommend maybe a new face shield....one without tunnelvision.
Never stop learning, and keep safety first and foremost always!
02-07-2001, 04:21 PM #11gicciFirehouse.com Guest
"As for Safetrain, please don't take this as a personal attack, as it is only intended as constructive criticism"
For not trying to make your reply a personal attack, you did a good job.
"I know you guys are not the only ones with this mind set, but not wanting anyone else to get your fire is an egotistical, sophomoric, and unsafe operating method."
I was going to reply with somesort of retalliatory remark but then decided against it. What is this reference to you guys, are you stereotyping me because I am from PG.
Let me tell you how it works. If you arrive at a fire ,and you are not aggresive and put the fire out quickly, someone will walk over you to put it out. Is this safe? Well maybe not. But I am pretty sure if that were your house/business or you were trapped inside you would be thanking god for that engine crew that pulled 2 lines and quickly extinguished the fire.
02-08-2001, 12:06 PM #12David PolikoffFirehouse.com Guest
"There is smoke pushing from every opening, but no visible flame from the outside."
Just by the above quote you should be thinking larger hose line be it a 2” or even a 2 ½ go with the smooth bore this will give you all the benefits of more GPM (265-326 GPM)with less nozzle reaction (compared to a fog line with the same GPM). This is not to say you will not have any nozzle reaction, you will still need your team to advance the line as well as when you are flowing. I think everybody answering this thread will agree, size up is the key to any fire. Forget all the math (not to say that it is not good information to know use it on your preplan) look at what the structure is doing. Heavy smoke color of smoke fire showing how much where ect.. as for the thermal imbalance thermal column or what ever you want to call it there is no reason to attack a fire using the indirect attack (ceiling) when you are in the room of origin. Go for the base of the fire this will provide rapid extinguishment and allow the upper level of the room to cool slowly plus you will find that your visibility will remain, due to the heated gasses not coming down on your head. Use the indirect attack to cool the ceiling when you are making your way to the fire room, but only if you have rollover or high heat conditions that you can feel through your gear. Cool the ceiling to stop a potential flashover. I agree with all the comments about truck work and ventilation, but use caution on light weight construction (steel bar joists on the roof) this can collapse very early in the fire. With all that said be safe out there.
David Polikoff www.workingfire.net
02-08-2001, 04:00 PM #13Jake295885Firehouse.com Guest
Dave has it on the money!
I worked with old school firemen early in my career, and hated when the old Captains called for a two and a half as the first line off the wagon. Fast foward 19 years the past ten as an officer I too call for the big line anytime lots of smoke is showing in a large structure.
As i watched this post, i wondered when someone would state the obvious, the big line produces the big knock down power, and is safer for the attack team.
Too many firefighters have lost the art of stretching and using deuce and a half hose.......Practice with it....Practice makes for good fireground performance.
We also keep a rope hose tool tied to the nozzle for the back-up man to use, its essential for advancing inside the building. without it you better be 6' 6" tall and built like a linebacker once you turn the first corner inside the building.....
02-08-2001, 07:57 PM #14E_man9RFDFirehouse.com Guest
Given the smoke conditions upon arrival, I would have placed the truckies to work, then push in to knock it out. If the scenario was the large luxury home with the heavy smoke, and know visable flame, I probably would have pulled the bazooka line (2 1/2 with smooth bore)
Not saying this is the perfect answer, but that's what I would have done.
Eng. Co. 9
"In all of us there are heroes... speak to them and they will come forth."
"In order for us to achieve all that is demanded of us, we must regard ourselves as greater than we are."
02-10-2001, 09:58 AM #15David PolikoffFirehouse.com Guest
Hey Jake thanks for the vote of confidence. I am a young guy with an old school firefighting mind. I like big water and I like going INSIDE a building to fight the fire.
David Polikoff www.workingfire.net
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