By Chris Pepler
The fire service workplace is dynamically changing every day. With the help of the National Institute of Standards and Technology and Underwriters Laboratories, we are finally able to back up and dispel many theories that have floated around for decades. We are finally able to dispel the myth about pushing fire as a transitional fire attack is initiated. We are finally able to identify a “flow path” as it relates to the crew making entry into the box. There are scientific data that tell us how new construction will react under fire conditions. Unfortunately, we have a long road ahead as a fire service trying to get these modern strategies and tactics delivered to and accepted by the entire fire service, since this is the opposite of what we were taught.
If we use National Institute for Occupational Safety and Health reports as a gauge to measure our fireground decision making, we will clearly see that we have a long way to go for improvement. And even with the tragic deaths that have happened over the past 14 years, we are still not delivering the message to the 1.1 million firefighters across the United States. Lack of 360˚assessments, lack of an understanding of fire behavior, uncoordinated fire attack, lack of command, and poor knowledge of hydraulics are a few of the most pressing issues we must face.
So, the question is, where are we lacking? Let’s take a detailed look at what a firefighter is required to learn and the emphasis put on each of the disciplines. Fire behavior, building construction, ventilation techniques, and tactics are just a few items we spend so little time on during the routine Firefighter I class.
Building Construction
Building construction has always had a significant impact on the outcome of a fire. For years, there was a strong emphasis on collapse, especially as we were introduced to lightweight construction. However, the trend of building larger homes with lighter materials has gone in a different direction in regard to rapid fire spread.
The International Residential Code defines “light-frame” construction as a “type of construction whose vertical and horizontal structural elements are primarily formed by a system of repetitive wood or light gage steel framing members.” To explain this in the simplest of terms, consumers are getting more for their money as a result of the construction industry’s creativity in using smaller undesired wood. Meanwhile, as firefighters, the rules of the game have changed.
Modern-day building construction has added an additional stress on incident commanders (ICs), often because their experience has been working in older legacy-constructed buildings. The reasons for the construction change were mainly greater energy efficiency, exterior wall coverings, and geometry replacing mass.
Case Study #1
Today’s buildings can mask the fire longer because of the tightness of the buildings. Triple-pane windows and well-insulated homes can hide a fire until it becomes ventilation limited and the first company arrives on scene and opens the front door, introducing the needed oxygen. The tight building can also hide the fire until it breaks the windows and releases the flames or starves the fire completely of oxygen. The biggest concern is the fact that as the IC, you do not know if the fire was burning for 20 minutes, 45 minutes, or two hours prior to the first alarm’s arrival. See the examples below.
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| (1) This photo was taken by the 911 caller after hanging up with the dispatcher. This picture is what initiated the call for the building fire. | |||||
| (2) This photo was taken approximately one minute after photo 1. The fire just broke through the triple-pane windows. | 3) This photo was taken approximately one minute after photo 2 was taken. Note the black smoke that is ready to intensify. |
As you can see, the fire was hidden until the heat was high enough to cause window failure. Until the window failed, there was very little indication of a working fire except for the puff of smoke that the caller reported seeing. This all took place prior to the fire department’s arrival.
(4) As the company begins its attack, thought must be given to the effects of the fire on the structural members. This should be part of the size-up, from the nozzleman to the company officer. Notice the black smoke on the Delta Division. There is lots of fuel in this path from siding, insulation, and the exterior sheathing.
The question we all have to ask as ICs is, how do we initially attack this fire? Because of the need to prove aggressiveness, the nozzle team often fights its way into the structure. We must change our ways and use portable monitors to make the quick knockdown to get a detailed visual of the structural members.
As a first-arriving officer, we must be sure that we consider the following factors in regard to building construction:
1. Burn Time. We have to consider that this has been burning for quite a while. The initial theory is that this fire was burning for approximately three hours prior to the fire department’s arrival. The windows, insulation, and siding hid this fire. Twenty or 30 years ago, we would have seen fire venting from the windows much earlier than with modern-day, lightweight construction.
2. Structural Collapse. As always, a thorough size-up needs to be conducted before we determine the overall strategy. If we pay attention to the details, we can see heavy fire emitting from the structure. We must assume that because of the age of the structure, this building has wood I-joists and know that there is less mass to burn through. Therefore, we must consider the potential for collapse.
(5) All of the mass (oriented strand board) has been burned away. The only two components left are the top and bottom flange of the TGI. To make matters worse, a lot of water is being discharged from the nozzles on the floor above, adding additional weight to the contents of the second floor.
Rapid Fire Spread
The next challenge facing today’s ICs is the potential for rapid fire spread throughout the structure. Exterior coverings, open soffits, and numerous void spaces caused by truss construction allow for rapid fire spread. There is a significant threat to firefighters if a structure is influenced by the building’s construction features.
The first concern to firefighters is the fire spreading through the soffit. The soffit’s purpose is to assist in providing adequate ventilation to the attic space. Ventilation is imperative to keep the attic space cool during the summer months. During the colder months, ventilation reduces moisture to keep the attic space dry, and in colder climates, it prevents the potential for ice dams, which can cause much damage.
Another dangerous issue to firefighters is the potential for autoignition up into the eaves, eventually spreading into the attic area. It is imperative that the initial line “rake the eaves,” stopping the fire from extending into the attic area. This tactic is critical for stopping spread into the attic. It is done by attacking the fire perpendicularly to the fire’s direction. Immediately on knocking down the fire, the crew must search the voids above for fire using their pike poles or hooks.
Case Study #2
On April 26, 2007, Firefighter Kyle Wilson lost his life in the line of duty while operating at a single-family dwelling fire. There were two major contributing factors–the wind from a storm and lightweight construction. The home was built in 2002. It was a 6,000-square-foot, colonial-style house. It was constructed of Type V building materials and had a brick veneer front with vinyl on the three other sides.
The weather played a significant role. Winds that morning averaged 23.5 miles per hour (mph) with gusts averaging 42 mph. The winds were increasing as a storm was strengthening off the Atlantic coast. The fire was believed to have started on the C division, and the wind blew the fire toward the structure.
The most disturbing factor about this line-of-duty death is that this was a new construction home that was only five years old. The fire began on the exterior and spread rapidly in all directions, from the exterior and extending into the interior on multiple levels.
Vinyl siding and the insulate sheathing will burn if there is an ignition source. In fact, vinyl siding can go from flame extension to the eaves in just 2:10 seconds!
Siding, insulation, OSB Sheating. Fire travels straight to the soffit.
The vinyl siding essentially serves as a wick, drawing the fire straight up to the soffit. On breeching the soffit, the fire will enter the attic voids and spread rapidly horizontally and vertically.
Tactically, there are two things we must be cognizant of. The first is that prior to entering a structure, we should rake the eaves and try to stop the spread of fire into the attic. Good pressure should allow the stream to break up into different directions, allowing for a quick cool down. Second, upon a quick knockdown, the officer should begin to poke holes in the ceiling checking for fire running in the attic area. No holes should be made without a line available!
Hydraulics 101
In an age where everything is technologically driven, we seem to be losing our touch in understanding the art of hydraulics. Many of us do not know our arsenal as well as we should. In the present fire environment, we must be able to give the proper gpm at the nozzle for an aggressive firefight. Fires have changed over time because the fuel loads are different. The fire load is based on the total amount of energy released, ignitability, and the speed at which the energy is released. Simply put, it is imperative that our drivers/operators be sure to deliver the adequate gpm to the seat of the fire. To deliver the proper gpm, we need to know some critical factors: nozzle type, gallons needed to be delivered, and the friction loss in the hose. Firefighters must be aware that it is not the pressure of the stream that extinguishes the fire but the gallons delivered to the seat of the fire each minute.
Flow
Let’s begin by making sure we know the handline capabilities. The two most common handlines used are the 1¾-inch line and the 2½-inch line. To keep things simple, we can remember the following:
• 1¾ converted to a decimal is 1.75. If you drop the decimal, you have 175. During an aggressive interior attack, 175 gpm is the minimum gpm that should be flowed through a 1¾-inch line. This flow matches the gpm that flows from a 15/16-inch smooth bore nozzle.
• 2½ converted to a decimal is 2.5. If you drop the decimal and add a zero, you will have 250. Therefore, 250 gpm is the minimum gpm that should be flowed through a 2½-inch handline when initiating an attack. This flow matches up with a 11/8-inch tip that is designed to deliver 266 gpm.
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Hose Size |
Nozzle Size |
GPM |
|
2½” |
11/8” |
250-300 |
|
1¾” |
15/16” |
180 |
Nozzle Pressures
Nozzle pressures vary as we continue to improve technology. Since the days of Lloyd Layman, there were some constants in regard to nozzle pressure. A smooth bore operates at 50 pounds per square inch (psi), a fog nozzle operates at 100 psi, and a master stream device operates at 80 psi. One of the biggest fallacies is that if I keep turning up the pressure, I will deliver more gpm. Theoretically, this may sound good, but too high of a discharge pressure will make the handline harder to handle and will make the water droplets break up, making them smaller and unable to absorb heat and not effectively extinguish the fire.
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Smooth Bore |
Fog Automatic
|
Master Stream |
|
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50 PSI |
100 PSI |
80 PSI |
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Friction Loss
The next part of the equation for determining our pump discharge pressure is to determine the friction loss. This is where many firefighters can get confused. We are going to simplify friction loss on the two handlines that we most commonly use.
Beginning with the 1¾-inch line, there are only three flows we will most likely use when extinguishing a fire. The three flows serve as our benchmarks, ultimately allowing us to get the water flowing down the street. These flows are for the “routine” calls to which an engine company responds.
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Gallons Per Minute |
FL Per 100 Feet |
Type of Fire |
|
120 |
25 |
Brush/Grass/Rubbish/ Small Car Fire |
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150 |
35 |
Well-involved car fire |
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180 |
50 |
**Interior Fire Attack (Always) |
To keep this simple, remember this: 120 – 150 – 180 ——– to 25 psi – 35 psi – 50 psi. All friction loss should be determined in 100-foot lengths. 120-150-180 ———– to 25-35-50
2 1/2 ” hose is even simpler to determine the friction loss per 100 feet of 2½-inch hose. As mentioned earlier, if a 2½-inch line is being deployed, a minimum of 250 gpm shall be flowed to ensure an adequate attack is possible. So, there should be two flows for 2½-inch, 250 gpm and 330 gpm for the 1¼-inch nozzle. Now, you use the “drop 10” method.
1. Determine the flow = 330 gpm
2. Take 330 and drop the 0 = 33
3. Subtract 33 – 10 = 23
4. This gives you 23 psi per 100 feet
5. 200 feet of 2½-inch hose will give you a friction loss of 46 psi
Connecting the Dots
Scenario
You arrive on the scene of a two-story wood-frame single-family dwelling. Fire is showing from three windows on Division 1 Alpha. The firefighter deploys the 1¾-inch handline to the front door. There is 200 feet of 1¾-inch hose with a 15/16-inch nozzle at the end of the hose. What is your pump discharge pressure?
· What is my desired gpm (flow)? 180 gpm
· What is my friction loss on 1¾-inch hose while flowing 180 gpm? 50 psi
· How many feet of hose have been deployed? 200 feet
· What is my nozzle pressure? 50 psi Smooth Bore
|
Nozzle Pressure |
Friction Loss @100 Feet |
Friction Loss @ 100 Feet |
Pump Discharge Pressure |
|
50 PSI + |
50 PSI + |
50 PSI = |
150 PSI |
Scenario
You arrive on the scene of a 30- × 90-foot single-story Type III construction store. Your officer orders the 2½-inch line be stretched into the building. You have 200 feet of 2½-inch hose with a 1¼-inch nozzle. What is your pump discharge pressure going to be?
1. What is my desired gpm (flow)? 330 gpm
2. What is my friction loss on 2½-inch hose while flowing 330 gpm? 33-10 = 23 psi per 100 feet
3. How many feet of hose have been deployed? 200 feet
4. What is my nozzle pressure? 50 psi Smooth Bore
|
Nozzle Pressure |
Friction Loss @100 Feet |
Friction Loss @ 100 Feet |
Pump Discharge Pressure |
|
50 PSI + |
23 PSI + |
23 PSI = |
96 PSI |
Knowing Our Arsenal
A question we often hear when taking strategy and tactic classes is, what size line would you pull in this scenario? This question provokes a lot of thought and debate. Many firefighters will state that they will pull a 2½-inch line for the knockdown power it provides. This can be a good answer provided the line is charged at the right pressure to deliver the “knockdown power.” The question I like to ask is, how well do you know your arsenal? This is very important because there are limitations to all of the tools in our tool box. So when answering the question by stating you would deploy the 2½-inch line, would you actually consider the weight of the hose? How maneuverable the hose is? If we look at the weight difference between the two attack lines, we will see a difference of 54 percent in weight! This will definitely hinder the operation if there is not adequate staffing on scene. We have to take the maneuverability and speed of deployment into account before making such decisions.
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Hose Size |
Hose Feet |
Weight |
|
1¾” |
100’ |
142 Lbs. |
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2½” |
100’ |
266 Lbs. |
The value of master stream devices is often underestimated at well-involved fires. The operators/drivers must have discipline when charging their device. Master stream devices vary by type and can include fixed type mounted directly to the apparatus or portable devices that can be placed into operation by one person. Operators/drivers must remain cognizant of the limitations of their tank capacity. A 13/8-inch master stream tip shall provide 500 gpm. However, if you have only 500 gallons of water onboard, you will have one minute of operating time until you either run out of water or establish a water supply. The driver can turn the device onto the fire for 30 seconds and rapidly deliver 250 gpm and make a quick knock on the fire single-handily while crews begin to stretch their handlines toward the building.
Most portable master stream devices are supplied with three-inch lines. The equation for determining flow from a portable master stream is simple. Portable master streams can flow 400 or 500 gpm. The Elkhart Rapid Attack Monitor operates at two pressures, 75 psi for 500 gpm and 50 psi for 400 gpm.
Determining the friction loss for a three-inch line is simple. Take the gpm, drop the two zeros, and square the remaining number.
1. 500 GPM desired flow
2. Drop zeros 500
3. 5 is left
4. Multiply 5 x 5 = 25
5. Friction Loss equals 25 PSI per 100′
|
GPM |
Nozzle Pressure |
Friction Loss @ 100 Feet |
Pump Discharge Pressure |
|
500 |
75 PSI + |
25 PSI = |
100 PSI |
|
400 |
50 PSI + |
16 PSI = |
66 PSI |
In this photo, the Rapid Attack Monitor (RAM) is in operation on the Delta division. The wind was blowing from the Bravo division toward the Delta exposure. The RAM was used for 30 seconds, flowing 500 gpm to knock down the heavy fire on Division 2. Keep in mind that the RAM just applied approximately 250 gpm in just 30 seconds. Knowing that the structural members are more than likely compromised, we must consider the additional weight of approximately 2,082 lbs.
With the recent report from UL on ventilation, it has become apparent that ventilation has a significant effect on fire behavior. The most significant thing we have discovered is what a flow path is. The flow path has even been isolated to the front door where we make entry.
Pros and Cons of Ventilation
The most important piece of the puzzle that was revealed from the UL report is the importance of controlling the flow path. The flow path control begins when we mask up at the front door and begin to make entry into the immediately dangerous to life or health atmosphere. Far too often, we mask up and bleed our line at the front door with the door open, allowing the flow path to make us react. If we immediately open the door and get a read of the apartment or floor and then immediately close the door until we are ready to make entry, we can essentially limit the air exchange needed at the seat of the fire and limit the size before the nozzleman applies water. In the UL experiments, flashover was delayed because of the limited air exchange. By delaying the potential for flashover, the hose team is safer, and we may actually be able to save more property. The conditions at the door can change rapidly. It is foolish to stretch a dry line onto any fire floor with the unpredictability of fire behavior.
In the above photos, the nozzle team has entered the structure through the front door. Within 15 seconds of entering the front door, the conditions changed as the fire came down the hallway following the flow path directly toward the front door. Imagine if a search crew was inside with no line!
Door control can be just as effective, if not more effective, as applying water to a typical room-and-contents fire. Oftentimes while crews are conducting primary searches and finding the room of origin, closing the door will slow down the progression of the fire, protecting interior crews and saving property.
The following three photos demonstrate how effective closing the door to the fire room can be. The first photo shows a well-involved room-and-contents fire on the Bravo-Charlie division. The second photo shows the interior crew closing the door as they go by to conduct a primary search. Photo 3 shows the immediate effect of closing the door, essentially drawing the fire into the room without one drop of water.
Tactical Ventilation
To keep things simple, tactical ventilation is when firefighters create the flow path needed to control the fire. Vertical ventilation is perhaps the best option for stopping the fire from consuming the building. Vertical ventilation must still be coordinated with the fire attack crews. The key point to remember is that although a hole is cut in the roof and the heat and gases will leave the structure, the air will get drawn into the structure, potentially allowing the fire to grow.
Case Study
Companies were dispatched to this three-story wood-frame Type V building for a reported kitchen fire. Staffing was short initially because of multiple calls in the city. The first-arriving company stretched a line to Division 2 Delta. Upon a quick knockdown, it was realized that the fire was already running the bays in the walls.
Initial views of the building on arrival
On further investigation, crews began opening up the walls, chasing the fire around the structure. While waiting for help to arrive, the fire intensified and ended up extending straight up to the cockloft. The fire was telling the IC what it was going to do because there was nobody available to open the roof and perform vertical ventilation. The following sequence demonstrates how the fire took control of the building.
At this point, it appears as though the fire is knocked down. Interior crews felt that the fire was out until they checked for extension behind the cabinets, although a quick read of the eaves showed the IC that the smoke was beginning to push out of the structure.
In an ideal staffing situation, it would be proactive to have a truck crew ready to open up the roof directly above these windows.
At this point, the fire is beginning to consume the structural members in the cockloft. It is telling us where it wants to go. The fire has now gone from the Division 2 Delta, to the roof of the A division.
The fire has now moved to Division Alpha 3. The truck crew is now in place and ready to perform ventilation, but it seems as though it is too late to control the fire. This is a classic case of the firefighters establishing a “flow path,” dictating where the fire should go.
Heat, gas, smoke, and fire leave the building vertically instead of spreading horizontally in which the structural members are consumed by fire.
The fire took control of the building and ran rampant in the void spaces. This is a pre-1900 building made of balloon frame construction. Things would have been different if the truck company was available to open up.
Conclusion
To reduce the number of firefighter deaths on the fireground, we have to begin by applying modern day strategies and tactics. The challenge will be trying to get the initial “buy in” from the entire group of naysayers. The fireground is changing, and the fire service can support many concepts from scientific data that have been provided. Fires have decreased drastically; they are more volatile than in the “old days.” Therefore, it is now more important than ever to train our members on the positive changes to send them all home safely.
BIO
CHRIS PEPLER has 21 years in the fire service and is the deputy chief of operations for the Torrington (CT) Fire Department. He coauthored the Fire Engineering’s, Tactical Perspectives DVD “Fire Attack” with Frank Ricci. He is also the co-host of Politics & Tactics with Frank Ricci on Fire Engineering radio. He is the director of training for Emergency Training Solutions.
