In the fire service, you can't possibly practice every scenario you will be faced with throughout your firefighting career. By it's very nature the fire service deals with chaos. So sometimes one of the best ways of preparing yourself is to subject yourself to "organized chaos". We just completed one such exercise, a controlled burn.
Our city,
Recently there have been 2 reasons for building demolitions via a controlled burn. One is a building that has been around for many years, and has been condemned. These are rare these days. The second is a perfectly good property that is being leveled to make way for a new, profitable development. This is becoming more prevalent here in
Our burn yesterday falls under the other category: Condemned Property. We are an old farming community. Today there is very little "prairie" left in
The house scheduled for demolition was a very old farm house on a prime piece of property. Right in it's backyard is a large community woodland park and small lake. The house is of balloon construction with a stucco exterior. The interior was very deteriorated. The plaster and lathe ceiling was sagging badly, and in several places had already fallen through. There was very little, if any, insulation. A situation ripe for spreading a fire. So in preparation for us getting some training experience out of the burn, we spent some time sheet-rocking the ceilings to prevent spread into the tinder-box attic. A precaution that was wise, but was not fully successful.
As we arrived at our Fire Station 1 for a briefing at 05:30, our training chief explained our team assignments and training objectives. Noteworthy items were the concern with the attic, and that we would be presented with a demonstration with a new type of foam.
Foam is a very important advancement in fire science. It has been around for many years now, but advancements are constantly being made and worked on. The particular brand of foam we have been using for year, manufactured by 3M, has been discontinued. We are now looking for a replacement. We currently carry Class A foam in our pumper's foam tanks, which we can use on the majority of the calls we receive. The foam changes the properties of water to make it "better" at cooling, extinguishing and controlling a fire. Class B foam is also important for use in flammable liquid fires. The foam creates a blanket over the liquid, smothering the fire. We have to carry class B foam separately, just in case we need it. The foam demonstration we received was for a combination A&B foam that would allow us to not need to carry 2 separate kinds of foam.
As we arrived at the old house at 06:00, we got to work. My crew was assigned one of the more labor-intensive tasks. This would become a motif throughout the day, it seems. We layed a supply line of 5in LDH (Large Diameter Hose) to the nearest Fire Hydrant. Since we require 2 sources of water, including a backup water source, we also setup a drop-tank. The drop tank is a square, self-standing pool that holds several hundred gallons of water. The second Engine in used Hard Suction intake hose to draw from this secondary water source should something happen to the primary water source or pumper.
We also hooked 200 feet of 2 1/2 inch hose to a gated wye. A gated wye takes one line, and splits it into 2. In our case we split off two 1 3/4 inch handlines, which would be used for attack. The gated wye allows us to charge the line, and control the water supply at the wye by using the gate valves on each output. We also laid another 200 foot section of 1 3/4 inch as a backup.
In anticipation of the attic being a threat, another crew cut a hole in the roof for vertical ventilation. During a real fire, if the fire conditions call for it, a hole is cut into the roof. Since heated gases and smoke accumulate quickly in the attic of a house fire, we want to vent these gases. Otherwise the heat and gases will continue to buildup, helping to spread the fire and make extinguishment even more difficult. Since heat rises, a hole allows for vertical escape of these gases, thus the term vertical ventilation. Horizontal ventilation also exists, and is used far more frequently. It is used primarily for smoke removal.
Once we were all prepared, we made a tour of the house in advance, as required by OSHA. That takes a lot of fun out of the experience, and a lot of realism as well. In a real fire you are navigating your way through a strange home, filled with contents you are unaware of since you can't see due to smoke, and trying to find the source of the fire, which is in origins usually unknown. While a training burn is great because it allows us to use combustible materials in a home, we know the layout of the house in advance, there are no contents beyond those which we will be burning, and you typically know exactly where the fire will be. But it's still funner than classroom training any day.
Since I, and a few other firefighters, had helped with preparation of the home a few days earlier, my Lieutenant had said he would try to get us on the first crew in on attack. I'm not sure if that was the reason why I was on the first crew, or if it was just coincidence, but that's where I was none-the-less. Being the first in is desirable because nothing has been disturbed yet, and we're the crew with the greatest likelihood of getting multiple attack evolutions. We weren't sure how many evolutions we would get in this old structure. We were hoping for 7 or 8, which would get us in there twice since there were 6 crews.
My crew had 2 rookies on it, so we put one on the nozzle, and the other right behind him as backup. That left me in third position with the thermal imager, and a Lieutenant behind me. Since I had the thermal imager, I would most likely be the only person with any sort of visual idea of what was happening with the fire.
We made entry, and advanced the line up the stairs and quickly located the fire room. We could see the fire room through the window on the entry side. And since it's a controlled burn, we knew it was the only room on fire. This information, in addition to knowing the layout of the house, resulted in us knowing far more information about the fire conditions than we would in any real fire. Consequently, we were in the fire room in under 10 seconds of entering the structure.
The conditions were extremely smoky, and the hallway and fire room were very small. The rookie on the nozzle quickly hit the fire, which immediately disturbed the thermal layering. Since heat rises, a fire left undisturbed will have the smokiest and hottest gases near the ceiling. They then bank down slowly as heat builds. Eventually the fire will "self-vent" by breaking a window due to heat, or it will burn it's way through the ceiling. When we hit it with water, the intense heat causes most of the water to turn to steam. Since water expands to 1700 times it's original volume when converted to steam, the thermal layer is disturbed, and the heat and gas is distributed throughout the room.
My job with the thermal imager was to instruct and inform the crew about the location and condition of the fire. After the initial short burst of water, the flames are quickly knocked down. Due to the steam and smoke, I could barely see the thermal imaging monitor, which was inches from my face. I wiped my SCBA mask and thermal screen, and saw that it was knocked down, but was still glowing hot. An officer called for hydraulic ventilation. A window was knocked out, and the nozzle is brought to the opening and put on a moderate fog stream. The water flowing out the window creates a draft effect, drawing most of the smoke and heat out of the window.
Of course an open window also draws in fresh oxygen, so the smoldering fire suddenly flared up with the introduction of fresh O2. It was quickly burning strongly again. We hit it again. Watching through the thermal I could see that it was not being hit properly. So I had to relay instructions to remove a palette that was obstructing the stream. I also had to direct the nozzleman to move his stream down and left to hit the seat of the fire.
After several evolutions of knocking it down, pulling off charred contents to find more fire, then hitting it again, we finally retreated from the structure and moved to the relief area to change our air bottles and get a quick break before we were put to work on another assignment.
That didn't last long, as I was pulled from relief to monitor the roof of the structure with a thermal imager from the outside to check for extension into the roof. After several minutes of the 2nd attack crew in the structure, suddenly heavy black smoke was emanating out of the ventilation hole on the roof. A clear sign of fire. The building was balloon construction, which means that it's constructed in such a manner that there are no vertical fire stops. A fire in the basement would quickly move up the walls into the attic. In this case the fire got behind the wall in the burn room, and it moved into the attic. This led to a semi-tense moment when we began to believe the controlled-burn would not be as controlled as we would have liked.
Fortunately, the attack crew was able to also get to the attic fire and put that out. They probably got the best training of anyone on that evolution. From that point on, only lower-level burns would be set.
The fire-starters had to stretch in order to keep the structure in good enough working order to be safe for 6 fires, one for each crew. We would not get a second evolution this day, however.
So we began preparations for burning the building down. We loaded it up with bales of hay, wood pallettes, and various other combustibles. Then the building was lit, and we sat back and watched.
My crew was put on pike pole duty. If anything needed to be manipulated, we would be the ones to approach the burning structure and do so.
So we sat back for several minutes, pike poles in hand, watching the fire build up internally. Everyone was speculating as to how they thought the burn would progress. Since the external stucco surface of the house is non-combustible, it would not go up like a traditional wood house. The fire built up to a raging inferno on the inside, like a kiln. Only once the wood was burned away on the inside and the stucco could not support itself would it fall in. This proved to be quite a bit of work for the pike pole crew.
One moment of particular levity came about 10 minutes into the burn, several minutes after the roof started to catch on pretty good. First, one squirrel came barreling out of the roof, jumping the 25 feet or so to the ground, and running straight up the nearest tree. I swear the tail of the squirrel was smoking, and it's belly was singed black. We barely had time to laugh about that, when a second squirrel, and then a third repeated this process. A fourth would follow several more minutes later. How those squirrels decided to stay inside the structure past the initial burn, the attic fire, and then 10 minutes of full-fledged roof fire, I'll never understand.
As the fire progressed, our station took the usual photos directly in front of the burning structure. The heat put off by a burning building is extremely intense. We had one thermal imager that would somehow figure out the temperature of the area the device was pointed at. We saw temperatures as high as 1,800 F on the external surface of the structure. That radiates a great deal of heat. I had my shield down, and Nomex hood on, and still felt the heat quite a bit as we went in with our pike poles to help the walls cave in.
In addition to the intense heat, I had left my sweatshirt on underneath my turnout gear. The outside temperature was about 10 F at 05:30, and I had intended on taking it off later. When the burn progressed to the point that the walls were not supported by much beyond their own weight, we went in to push them in. Turns out to be easier said than done. There was quite a bit of stability left in those walls. I had a 12 foot pike pool stuck into the wall. I had to lean into it with all the effort I could muster, and get the wall rocking in a rhythmic motion to finally topple it in. This was repeated about a dozen times. I was fairly exhausted by this process.
One of the more dangerous aspects of burning a house down is the chimney. This house had 2 chimneys, one external, and one internal. We were able to push one wall into the internal chimney, forcing it to topple. The other chimney was stout and well constructed. It would not topple with the adjoining walls.
We decided to put a smooth bore tip on a handline, crank the pump pressure as much as we could, and try hitting it at the top with the stream. A solid stream can put out quite a bit of force. It took four of us to hold that line it had so much pressure in it, yet it was unable to topple the chimney. It would rock just a few inches at the top, but it was not enough.
Once the house was just a smoldering basement, it was time to start breaking things down and make sure the house was in as safe a condition as possible. We took two handlines to hit the nooks and crannies, and hit the majority of it with a master stream from the engine. We flowed about 1200 GPM for 15 minutes into that basement. The steam put off initially looked like a Nuclear power plant. It's amazing how much heat can be contained by a smolder pile of rubble.
By the end of the day, we had put in about 8 hours of effort. We were all exhausted, but satisfied. These training exercises are so valuable. It helps to just practice things like laying to hydrants, setting up the drop tank, ventilation, etc. When it comes time for a real fire these types of evolutions make for a certain degree of routineness to an emergency. Well, as much as can be expected from chaos, anyway.
Thursday, May 10, 2007
Practice Makes Perfect
[Note: This is a blog post first published 2/21/2005. It is being reposted here because my old blog account is no longer valid]
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