As with many other questions, it is likely that the answer to the question of which nozzle is best is it depends. As discussed in Effective and Efficient Fire Streams, Safe, effective and efficient fire control requires:

• Water application to control the fire environment as well as direct attack on the fire
• Appropriate flow rate for the tactical application (cooling hot, but unignited gases may be accomplished at a lower flow rate than direct attack on the fire)
• Direct attack to exceed the critical flow rate based on the fire’s heat release rate
• Sufficient reserve (flow rate) be available to control potential increases in heat release rate that may result from changes in ventilation
• Water application in a form appropriate to cool its intended target (i.e., small droplets to cool hot gases or to cover hot surfaces with a thin film of water)
• Water to reach its intended target (fog stream to place water into the hot gas layer and a straight or solid stream to pass through hot gases and flames and reach hot surfaces)
• Control of the fire without excessive use of water

Accomplishing this requires different stream characteristics at different times. The characteristics that are optimal for gas cooling are likely quite different than for cooling hot surfaces, particularly when dealing with fully developed fire conditions in a large compartment. It is likely that direct attack on a fire with a high heat release rate in a large compartment may best be accomplished with a high flow stream having a high degree of stream cohesion and extremely large droplets. On the other hand, cooling the hot gas layer while accessing a shielded fire is most effectively and efficiently accomplished using a fog stream with a variable pattern angle, small droplet size, and a lower flow rate. No nozzle and hose system will be equally effective and efficient in all situations.

At present, there is no standardized method for testing and evaluating the effectiveness and efficiency of firefighting nozzles. However, there are a number of parameters that may be useful in the process of evaluating, selection, and specification of combination nozzles.

Application

Nozzle selection must be considered within the context of the nozzle, hose, and pump system that it will be used. If starting from scratch, it may be useful to consider each of these components. For example, high and ultra high pressure systems can provide considerably higher efficiency than low pressure systems, but they are limited to low flow rates. Low pressure systems on the other hand have larger droplet sizes and as such cannot achieve as high efficiency as higher pressure systems, but are scalable to deliver higher flow rates. If we have an existing system in place, the question may be what nozzle will provide the greatest effectiveness, efficiency, and range of capabilities.

It is also important to consider the type of buildings and occupancies in which firefighting operations will likely take place. Important factors include building and interior compartment size and occupancy. Another factor that must be considered is pressure limitations imposed by fixed fire suppression systems such as standpipes (in some cases outlet pressure is limited to 65 psi (448 kPa).

While there is no standard test methodology for determining the effectiveness and efficiency, there are a number of characteristics that can be assessed and evaluated when considering selection and specification of the handline nozzles.

Starting Point

Central Whidbey Island Fire & Rescue (CWIFR), where I serve as Fire Chief is about to start the process of evaluating nozzles for use on existing 1-3/4” (45 mm) handlines. CWIFR is a small fire district with a mix of residential and commercial occupancies located approximately 60 miles (97 km) north of Seattle, Washington. Structural fire risks are predominantly wood frame, single family dwellings with a small number of apartments, commercial buildings and institutional occupancies. The district protects an area of 50 square miles and a population of approximately 9000. Four Type I Engines and three Type I Tactical Water Tenders are staffed with a mix of full-time, part-time, and volunteer personnel operating out of four fire stations.

CWIFR currently uses Elkhart Chief 150 g/min (568 l/min) single flow rate nozzles that are designed to operate at a nozzle pressure of 75 psi (517 kPa) as the standard nozzle on 1-3/4” (45 mm) hoselines (similar to the nozzle shown in Figure 1, but CWIFR uses break apart nozzles with a separate tip and shutoff).

Figure 1. Elkhart Chief Nozzle

Given the same flow rate, a nozzle pressure of 75 psi provides a slight reduction in nozzle reaction in comparison with a nozzle pressure of 100 psi (about 13% when operating a straight stream). However, all things being equal, lower nozzle pressure generally results in larger droplets. Larger droplet size is not necessarily a disadvantage in direct or indirect attack, but can significantly reduce effectiveness of gas cooling. Using the current CWIFR nozzles, flow rate can be increased to approximately 180 gpm by increasing nozzle pressure to 100 psi. However, it is not possible to develop effective streams at flow rates significantly below 150 gpm as a nozzle pressure below 75 psi causes significant deterioration in stream quality, reach, and penetration.

CWIFR’s nozzle tests will serve several purposes: First will be to increase members’ familiarity with the nozzles currently in use, their capabilities, and limitations. The second will be to evaluate other types of nozzles that may provide a broader range of capabilities and increase operational effectiveness.

Three variable flow nozzles and two automatic nozzles will be included in the initial round of testing and evaluation. All of the nozzles selected allow for development of a range of flows at a standard nozzle pressure of 100 psi.

Variable Flow Nozzles

• Akron Turbojet
  30-60-95-125 g/min (115-230-360-475 l/min)
• Akron Wide Range Turbojet
  Flow Range 30-95-125-150-200 g/min (115-360-475-550-750 l/min)
• Elkhart Wide Range Phantom
  Flow Range 30-95-125-150-200 g/min (115-360-475-550-750 l/min)

Automatic Nozzles

• Ultimatic 10-125 g/min (38-475 l/min)
• Midmatic 70-200 g/min (265-750 l/min)

Three of these nozzles, the Wide Range Turbojet, Wide Range Phantom, and Midmatic have a higher designed flow capability than the nozzles currently used by CWIFR as well as the capability to develop effective streams at lower flow rates. Two of these nozzles, the Turbojet and Ultimatic have a lower flow capability than the nozzles currently used by CWIFR, but have been found to provide excellent gas cooling capability based on laboratory tests (Handell, 2000) and anecdotal evidence during live fire training and operational firefighting.

Basic Design

The starting point for nozzle evaluation is identification of basic characteristics:

• Designed Nozzle Pressure
• Flow Control: Fixed Flow, Variable Flow, Automatic
• Flow Rates/Range

Physical & Operational Characteristics

Physical and operational characteristics can be as important as stream performance as nozzles must be used under a wide range of operational conditions.

• Weight
• Size
• Size of Bail
• Flow Control Method
• Simplicity/Complexity of Operation

Performance Characteristics

Nozzle performance can be evaluated in a variety of different ways ranging from baseline data such as actual flow rates, range of patterns developed, and ease of operation. Other characteristics are a bit more complex such as pattern density and hang time.

• Actual flow rate vs. specified flow rate
• Maximum fog pattern angle
• Reach at designed pressure and flow
• Ease of Operation within designed pressure and flow range
• Pattern density during continuous operation
• Pattern density after pulsed application (2 second delay)
• Hang time for droplets in pulsed application
• Performance (as outlined above) outside designed pressure and flow

As identified above, performance will also be evaluated outside the designed pressure and flow range of the nozzles. For example, use of variable flow nozzles at the lowest flow setting at pressures above the designed nozzle pressure can produce extremely small droplets (more on this in a later post).

Finance and Logistical Considerations

While nozzle performance is the most important factor, it is also essential to assess the logistical and financial considerations.

• Initial purchase price
• Life-cycle cost
• Maintenance requirements

Next Steps

The next post in this series will examine the nozzles currently in use by CWIFR and provide additional detail on the evaluation process.

Reference

Handell, A. (2000) Utvärdering av dimstrålrörs effektivitet vid brandgaskylning [Evaluation of the efficiency of fire fighting spray nozzles in a smoke gas cooling situation], Report  5065. Department of Fire Safety Engineering, Lund University, Sweden

I am using this series of posts to work through the process of developing a chapter on the foundational scientific concepts related to practical fire dynamics and fire control theory. My hope is to take the middle ground between the oversimplified and unsupported explanations provided in most texts intended for firefighter training and the higher level materials intended for fire protection engineers. This is proving to be no small task! Your feedback on my success (or lack thereof) in providing scientifically sound, but reasonably simple explanations would be greatly appreciated.

Back to Everyday Concepts Part 1

When faced with the challenge of developing firefighters understanding of energy, temperature, heat, and power in a limited timeframe, I generally avoid detailed discussion of the actual definition of the SI unit for energy, the Joule, and the mechanical equivalent of thermal energy. I have found that illustrating the concept of the Joule as it relates to thermal energy in terms of heating water to serve the purpose. However, as I looked back at the first post in this series, I think it would be useful to go back to the source, and examine James Joule’s experiments that made the connection to the equivalence of mechanical and thermal energy.

While not commonly used in scientific work, the American fire service has typically used the British thermal unit (Btu) as a measure of thermal energy. The Btu is defined in terms of the heating effect of energy transferred to water. One Btu is the energy required to raise the temperature of one pound of water by one degree Fahrenheit.

As discussed in the first post in this series, the SI unit of measure for energy is the Joule (J) which is defined in mechanical terms, but is applicable to all forms of energy.

In the mid 1800’s English physicist James Joule demonstrated the equivalence of mechanical and thermal energy by using a mechanical apparatus to stir water in an insulated container with paddles driven by a falling weight (see Figure 1).

Joule (1845) reported that based on analysis of data from a number of experiments, that expenditure of mechanical energy of 817 ft/lbs (the energy required to raise 817 pounds to a height of one foot) was the equivalent of an increase in temperature of one pound of water by one degree Fahrenheit. Conversion to SI units of measure is a bit complex, but 817 ft/lbs is equal to 1107 Newton/meters (the energy required to raise a mass of 1107 N to a height of 1 meter). While a non-standard measure of energy, the Newton/meter (N/m) provides a direct comparison to ft/lbs. In mechanical terms, a N/m equals the SI unit for energy, the Joule. Expressed in SI units, 1107 Joule of energy were required to raise the temperature of 0.454 kg (1.0 lbs) of water 0.56^o C (1^o F). This is quite close to the currently accepted conversion value in which 1055 J = 1 Btu.

Figure 1. Demonstration of the Mechanical Equivalent of Heat

Note: Joule used a lesser weight falling over a greater distance, repeated a number of times. This drawing is simplified to provide a conceptual illustration.

Heat Transfer

In everyday language the word heat is used in a variety of ways (many of which are incorrect from a thermodynamic perspective). In thermodynamics, heat is a method of energy transfer. Heat is not a form of energy (a commonly stated misconception), but simply the name of the process of energy transfer based on temperature difference. Objects do not “have” heat, they have thermal energy, and heat is thermal energy in the process of transfer to objects having a lower temperature.

Even though it involves energy transfer, heat is not the same as work. Remember that work involves force causing movement in a direction influenced by that force (and if no movement in that direction occurred, no work is done). Energy transferred by heat results in an increase in molecular movement, but not in a specific direction, therefore no work is done. However, this does not mean that energy transferred by heat cannot be transformed into mechanical energy and accomplish work.

Transfer of energy from one object to another must be classified as heat or work. When energy content changes, it must be the result of heat, work, or a combination of both. Heat and work are processes by which energy is exchanged rather than energy itself.

The word flow is often used in discussing heat transfer (e.g., energy flows from objects with higher temperature to those with lower temperature). This helps visualize patterns of movement, but it is important to remember that neither energy nor heat is a fluid. Heat is the process of energy transfer due to temperature differences. This energy transfer takes place in a variety of different ways.

Second Law of Thermodynamics: There are several ways to state this law. The simplest is that heat cannot spontaneously flow from a material at lower temperature to a material at higher temperature. However, thermal energy moves from materials at high temperature to those having lower temperatures until they have the same temperature (equilibrium).

There are three methods of heat transfer, conduction, convection, and radiation. Each of these has significant impact on the processes of combustion, fire development, and fire control.

Conduction

Conduction of heat occurs when adjacent atoms vibrate against one another or as electrons move from atom to atom. Heat transfers through solid materials and between solid materials in direct contact with one another by conduction. The atoms in liquids and gases are further apart, reducing the probability of collision and transfer of thermal energy.

Figure 2. Conduction

Factors Influencing Conductive Heat Transfer

The factors influencing conduction are temperature difference, length (or thickness), cross sectional area, and the thermal conductivity of the conductor.

Thermal conductivity is the measure of the quantity of thermal energy which flows through a conductor. In addition to form, there are a number of factors influencing thermal conductivity of materials including molecular bonding, structure, and density. Units of measure for conductivity must account for the amount of energy transferred in a given amount of time, thickness (or distance), and temperature difference. The SI units of measure for thermal conductivity are Watts per Kelvin per Meter (W?K?m). While appearing to be complex, this measure is fairly straightforward; indicating the number of Watts (Joules/second) transferred a distance of one meter for each Kelvin of temperature difference (Figure 3)

Figure 3. Thermal Conductivity

When the temperature of one surface of a solid material is higher than another, heat will move through the material. Depending on the characteristics of the material, this conductive heat transfer may be slow or it may occur quickly. The rate of heat transfer is defined by the coefficient of thermal conductivity.

As illustrated in Figure 3, the total amount of heat transfer is dependent on the coefficient of thermal conductivity, difference in temperature, and cross sectional area of the conductor. It is difficult to measure thermal conductivity as it describes a semi-static situation with a constant temperature gradient. However, heat transfer results in temperature changes towards equilibrium (equal temperature at all points in the conductor).

A high coefficient means heat moves very quickly; a low coefficient means heat moves very slowly. As illustrated in Table 1, the thermal conductivity constant (k) for different materials varies considerably.

Table 1Thermal Conductivity Table

Metals are usually the best conductors of thermal energy due to their molecular bonding and structure. Metallic chemical bonds have free-moving electrons and form a crystalline structure which aids in transfer of thermal energy as illustrated in Figure 4.

Figure 4. Conduction in Metals

Because the outer electrons in metals are shared by all the atoms, they are not considered to be associated with any one atom. Since these electrons are attracted to many atoms, they have considerable mobility that allows for the good thermal conductivity seen in metals.

In general, density decreases so does conduction (some unusual materials such as carbon foam, have low density and high conductivity). Therefore, most fluids (and especially gases) are less conductive. This is due to the large distance between atoms in a gas: fewer collisions between atoms means less conduction. Conduction is dependent on the area being heated, temperature differential, and thermal conductivity of the material.

What’s Next

The next post in this series will examine convection and radiation as mechanisms of heat transfer. In addition, I will be starting a series of posts to discuss a comprehensive approach for nozzle testing from an operational perspective.

Ed Hartin, MS, EFO, MIFireE, CFO

References

Joule, J. (1845). On the existence of an equivalent relation between heat and the ordinary forms of mechanical power. Philosophical Magazine, 3(xxvii), p. 205.

Quick Review

The previous post in this series presented a video clip of an incident on the afternoon of February 18, 2010 that injured four Chicago firefighters during operations at a residential fire at 4855 S. Paulina Street.

First arriving companies discovered a fire in the basement of a 1-1/2 story, wood frame, single family dwelling and initiated fire attack and horizontal ventilation of the floors above the fire. Based on news accounts, the company assigned to fire attack was in the stairwell and another firefighter was performing horizontal ventilation of the floors above the fire on Side C when a backdraft or smoke explosion occurred. Two firefighters on the interior, on at the doorway and the firefighter on the ladder on Side C were injured and were transported to local hospitals for burns and possible airway injuries.

In analyzing the video clip shot from inside a nearby building, we have several advantages over the firefighters involved in this incident.

Time: We are not under pressure to make a decision or take action.

Reduced Cognitive Workload: Unlike the firefighters who needed to not only read the fire, but also to attend to their assigned tactics and tasks, our only focus is analysis of the fire behavior indicators to determine what (if any) clues to the potential for extreme fire behavior may have been present.

Repetition: Real life does not have time outs or instant replay. However, our analysis of the video can take advantage of our ability to pause, and replay key segments, or the entire clip as necessary.

Perspective: Since the field of view in the video clip is limited by the window and the fidelity of the recording is less than that seen in real life, it presents a considerably different field of view than that of the firefighters observed in operation and does not allow observation of fire behavior indicators and tactical operations on Sides A, B, and D.

Initial Size-Up

What B-SAHF indicators could be observed on Side C up to the point where firefighters began to force entry and ventilate the basement (approximately 02:05)?

Figure 1. Conditions at 01:57 Minutes Elapsed Time in the Video Clip

Building: The structure is a 1-1/2 story, wood frame, dwelling with a daylight basement. The apparent age of the structure makes balloon frame construction likely, and the half story on the second floor is likely to have knee walls, resulting in significant void spaces on either side and a smaller void space above the ceiling on Floor 2. One window to the left of the door on Side C appears to be covered with plywood (or similar material). Given the location of the door (and door on Side A illustrated in the previous post in this series), it is likely that the stairway to the basement is just inside the door in Side C and a stairway to Floor 2 is just inside the door on Side A.

Smoke: A moderate volume of dark gray smoke is visible from the Basement windows and windows and door on Floor 1 as well as a larger volume from above the roofline on Side B. While dark, smoke on Side C does not appear to be thick (optically dense), possibly due to limited volume and concentration while smoke above the roofline on Side B appears to be thicker. However smoke on Side C thickens as time progresses, particularly in the area of the door on Floor 1. The buoyancy of smoke is somewhat variable with low buoyancy on Side C and greater buoyancy on Side B. However, smoke from the area of the door on Floor 1 Side C intermittently has increased buoyancy.

Air Track: Smoke on Side C appears to have a faintly pulsing air track with low velocity which is masked to some extent by the effects of the wind (swirling smoke due to changes in low level wind conditions). Smoke rising above the roofline on Side B appears to be moving with slightly greater velocity (likely due to buoyancy).

Heat: The only significant heat indicators are limited velocity of smoke discharge and variations in buoyancy of smoke visible from Sides B and C. Low velocity smoke discharge and low buoyancy of the smoke on Side C points to relatively low temperatures inside the building. The greater buoyancy and velocity of smoke observed above the roofline on Side B indicates a higher temperature in the area from where this smoke is discharging (likely a basement window on Side B).

Flame: No flames are visible.

Initial Fire Behavior Prediction

Based on assessment of conditions to this point, what stage(s) of development and burning regime(s) is the fire likely to be in?

Dark smoke with a pulsing air track points to a ventilation controlled, decay stage fire.

What conditions would you expect to find inside the building?

Floors 1 and 2 are likely to be fully smoke logged (ceiling to floor) with fairly low temperature. The basement is likely to have a higher temperature, but is also likely to be fully smoke logged with limited flaming combustion.

How would you expect the fire to develop over the next few minutes?

As ventilation is increased (tactical ventilation and entry for fire control), the fire in the basement will likely remain ventilation controlled, but will return to the growth stage as the heat release rate increases. Smoke thickness and level (to floor level) along with a pulsing air track points to potential for some type of ventilation induced extreme fire behavior such as ventilation induced flashover (most likely) or backdraft (less likely). Another possibility, would be a smoke explosion; ignition of premixed gas phase fuel (smoke) and air that is within its flammable range (less likely than some type of ventilation induced extreme fire behavior)

Ongoing Assessment

What indicators could be observed while the firefighter was forcing entry and ventilating the daylight basement on Side C (02:05-02:49)?

There are few changes to the fire behavior indicators during this segment of the video. Building, Heat, and Flame indicators are essentially unchanged. Smoke above the roofline appears to lighten (at least briefly) and smoke on Side C continues to show limited buoyancy with a slightly pulsing air track at the first floor doorway.

What B-SAHF indicators can be observed at the door on Side C prior to forced entry (02:49-03:13)?

Figure 2. Conditions at 03:06 Minutes Elapsed Time in the Video Clip

Figure 3. Conditions at 03:08 Minutes Elapsed Time in the Video Clip

Building, Smoke, Heat and Flame indicators remain the same, but several more pulsations (03:05-03:13) providing a continuing, and more significant indication of ventilation controlled, decay stage fire conditions.

What indicators can be observed at the door while the firefighter attempts to remove the covering over the window adjacent to the door on Floor 1 (03:13-13:44)?

No significant change in Building, Heat, or Flame Indicators. However, smoke from the doorway has darkened considerably and there is a pronounced pulsation as the firefighter on the ladder climbs to Floor 2 (03:26). It is important to note that some of the smoke movement observed in the video clip is fire induced, but that exterior movement is also significantly influenced by wind.

What B-SHAF indicators do you observe at the window on Floor 2 prior to breaking the glass (03:44)?

Figure 4. Conditions at 03:43 Minutes Elapsed Time in the Video Clip

The window on Floor 2 is intact and appears to be tight as there is no smoke visible on the exterior. It is difficult to tell due to the angle from which the video was shot (and reflection from daylight), but it would be likely that the firefighter on the ladder could observe condensed pyrolizate on the window and smoke logging on Floor 2. It is interesting to note limited smoke discharge from the top of the door and window on Floor 1 in the brief period immediately prior to breaking the window on Floor 2.

What indicators are observed at the window on Floor 2 immediately after breaking the glass (03:44-03:55)?

Figure 5. Conditions at 03:52 Minutes Elapsed Time in the Video Clip

No significant changes in Building, Heat, or Flame indicators. Dark gray smoke with no buoyancy issues from the window on Floor 2 with low to moderate velocity immediately after the window is broken.

What B-SAHF indicators were present after the ventilation of the window on Floor 2 Side C was completed and 04:08 in the video clip (03:44-04:08)?

Buoyancy and velocity both increase and a slight pulsing air track develops within approximately 10 seconds. In addition, the air track at the door on Floor 1 shifts from predominantly outward with slight pulsations to predominantly inward, but with continued pulsation (possibly due to the limited size of the window opening on Floor 2, Side C.

Anticipating Potential Fire Behavior

Unlike the firefighters in Chicago who were operating at this incident, we can hit the pause button and consider the indicators observed to this point. Think about what fire behavior indicators are present (and also consider those that are not!).

Initial observations indicated a ventilation controlled decay stage fire and predicted fire behavior is an increase in heat release rate with potential for some type of extreme fire behavior. Possibilities include ventilation induced flashover (most likely) or backdraft (less likely), or smoke explosion (less likely than some type of ventilation induced extreme fire behavior).

Take a minute to review the indicators of ventilation controlled, decay stage fires as illustrated in Table 1.

Table 1. Key Fire Behavior Indicators-Ventilation Controlled, Decay Stage Fires

Which of these indicators were present on Side C of 4855 S. Paulina Street?

Building: The building appeared to be unremarkable, a typical single family dwelling. However, most residential structures have more than enough of a fuel load to develop the conditions necessary for a variety of extreme fire behavior phenomena.

Smoke: The dark smoke with increasing thickness (optical density) is a reasonably good indicator of ventilation controlled conditions (particularly when combined with air track indicators). Lack of buoyancy indicated fairly low temperature smoke, which could be an indicator of incipient or decay stage conditions or simply distance from the origin of the fire. However, combined with smoke color, thickness, and air track indicators, this lack of buoyancy at all levels on Side C is likely an indicator of dropping temperature under decay stage conditions. This conclusion is reinforced by the increase in buoyancy after ventilation of the window on Floor 2 (increased ventilation precipitated increased heat release rate and increasing temperature).

Air Track: Pulsing air track, while at times quite subtle and masked by swirling smoke as a result of wind, is one of the strongest indications of ventilation controlled decay stage conditions. While often associated with backdraft, this indicator may also be present prior to development of a sufficient concentration of gas phase fuel (smoke) to result in a backdraft.

Heat: Velocity of smoke discharge (air track) and buoyancy (smoke) are the only two heat indicators visible in this video clip. As discussed in conjunction with smoke indicators, low velocity and initial lack of buoyancy which increases after ventilation is indicative of ventilation controlled, decay stage conditions.

Flame: Lack of visible flame is often associated with ventilation controlled decay and backdraft conditions. However, there are a number of incidents in which flames were visible prior to occurrence of a backdraft (in another compartment within the structure). Lack of flames must be considered in conjunction with the rest of the fire behavior indicators. In this incident, lack of visible flames may be related to the stage of fire development, but more likely is a result of the location of the fire, as there is no indication that flames were present on Side C prior to the start of the video clip.

What Happened?

Firefighters had entered the building for fire attack while as illustrated in the video clip, others were ventilating windows on Side C. It is difficult to determine from the video if a window or door at the basement level on Side C was opened, but efforts were made to do so. A window on Floor 2 had been opened and firefighters were in the process of removing the covering (plywood) from a window immediately adjacent to the door on Floor 1. At 04:12, an explosion occurred, injuring two firefighters on the interior as well as the two firefighters engaged in ventilation operations on Side C.

Starting at approximately 03:59, velocity of smoke discharge from the window on Floor 2 Side C increases dramatically. At 04:08 discharge of smoke begins to form a spherical pattern as discharged from the window. This pattern becomes more pronounced as the sphere of smoke is pushed away from the window by increasing velocity of smoke discharge at 04:12, immediately prior to the explosion. Velocity of smoke discharge at the door increases between 03:59 and -4:12 as well, but as the opening is larger, this change is less noticeable. As pressure increases rapidly during the explosion a whooshing sound can be heard. After the explosion, there was no noticeable increase in fire growth.

Figure 6. Conditions at 04:08 Minutes Elapsed Time in the Video Clip

Figure 7. Conditions at 04:09 Minutes Elapsed Time in the Video Clip

Figure 8. Conditions at 04:10 Minutes Elapsed Time in the Video Clip

Figure 9. Conditions at 04:11 Minutes Elapsed Time in the Video Clip

Figure 10. Conditions at 04:12 Minutes Elapsed Time in the Video Clip

Figure 11. Conditions at 04:13 Minutes Elapsed Time in the Video Clip

Based on observation of fire behavior indicators visible in the video clip, we know that a transient extreme fire behavior event occurred while a crew was advancing a hoseline on the interior and ventilation operations were being conducted on Side C. What we don’t know is what firefighting operations were occurring on the other sides of the building or in the interior. In addition, we do not have substantive information from the fire investigation that occurred after the fire was extinguished.

The Ontology of Extreme Fire Behavior presented in an earlier post classifies these types of phenomena on the basis of outcome and conditions. As a transient and explosive event, this was likely a backdraft or smoke explosion. In that this occurred following entry and during ongoing ventilation operations, I am inclined to suspect that it was a backdraft.

Indicators visible on Side C provided a subtle warning of potential for some type of ventilation induced extreme fire behavior, but were likely not substantially different from conditions observed at many fires where extreme fire behavior did not occur.

As the title of the wildland firefighting course S133 states; Look Up, Look Down, Look Around! Anticipation of fire development and extreme fire behavior requires not only recognition of key indicators, but that these indicators be viewed from a holistic perspective. Firefighters and/or officers performing a single task or tactical assignment may only see part of the picture. It is essential that key indicators be communicated to allow a more complete picture of what is occurring and what may occur as incident operations progress.

Ed Hartin, MS, EFO, MIFireE, CFO

Updated March 7, 2010 with Longer Video Clip of this Incident

On the afternoon of February 18, 2010, firefighters in Chicago responded to a residential fire at 4855 S. Paulina Street. First arriving companies discovered a fire in the basement of a 1-1/2 story, wood frame, single family dwelling and initiated fire attack and horizontal ventilation of the floors above the fire.

Based on news accounts, the company assigned to fire attack was in the stairwell and another firefighter was performing horizontal ventilation of the floors above the fire on Side C when a backdraft or smoke explosion occurred. Three firefighters on the interior and the firefighter on the ladder on Side C were injured and were transported to local hospitals for burns and possible airway injuries.

Figure 1. Consider Key Fire Behavior Indicators

B-SAHF Indicators

Recognizing subtle fire behavior indicators during incident operations can be difficult and important indicators are often only visible from one location (other than where you are). What Building, Smoke, Heat, and Flame (B-SAHF) indicators would you anticipate seeing if potential backdraft conditions exist (or may develop as the incident progresses)? How would this differ from the indicators that conditions may present risk of a smoke explosion?

For more information on key fire behavior indicators related to ventilation controlled burning regime, decay stage fires, backdraft, and smoke explosion, see the following posts:

• Recent Extreme Fire Behavior
• Decay Stage Fires: Key Fire Behavior Indicators
• Real “Backdraft”
• Hazard of Ventilation Controlled Fires
• Smoke Explosion or Backdraft?
• Language & Understanding: Extreme Fire Behavior
• 15 Years Ago: Backdraft at 62 Watts Street
• 62 Watts Street: Modeling the Backdraft
• Extreme Fire Behavior: An Organizational Scheme (Ontology)
• Fires and Explosions
• Gas Explosions
• Gas Explosions Part 2
• Extreme Fire Behavior: An Organizational Scheme
• Fuel and Ventilation

Incident Video

A video of the incident at 4855 S. Paulina Street was recently posted on YouTube (a shorter version is posted on Firevideo.net). It appears that the video may have been shot through a window by an occupant of the D2 exposure. The title of this video is “Chicago Smoke Explosion”. After watching the video and answering the questions posed in this post, do you think that this was a backdraft or smoke explosion? Why?

One of the great assets of using video as a learning tool is the ability to stop the action and go back to review key information. Watch the video and stop the action as necessary to answer the following questions”

• Pause at 02:05. What B-SAHF indicators could be observed on Side C up to this point in the video clip?
• Pause at 02:49. What indicators could be observed while the firefighter was forcing entry and ventilating the daylight basement on Side C?
• Pause at 03:13. What B-SAHF indicators can be observed at the door on Side C prior to forced entry?
• Pause at 03:35. What indicators can be observed at the door after forcing the outer door (prior to ventilation of the window on Floor 2)?
• Pause at 03:44. What B-SHAF indicators do you observe at the window on Floor 2 prior to breaking the glass?
• Pause at 03:55. What indicators are observed at the window on Floor 2 immediately after breaking the glass?
• Pause at 04:08. What B-SAHF indicators were present after the ventilation of the window on Floor 2 Side C was completed and 04:08 in the video clip?

After answering the questions, watch the complete clip. Do you think that this was a backdraft or smoke explosion? If you thought that this was a backdraft: Did you see potential indicators? If so what were they? If not, why do you think that this was the case? If you think that this was a smoke explosion, what indications lead you to this conclusion? What indicators were present?

You may want to watch this video clip several times and give some thought to what factors were influencing the B-SAHF indicators (particularly smoke, air track, and heat). Were these indicators consistent with your perception of backdraft indicators? Is so, how? If not, what was different? What indicators may have been visible from other vantage points. Remember that the video provides a view from a single perspective (and one that is considerably different than the crews working at this incident).

The next post in this series will take a closer look at the video and key fire behavior indicators.

Ed Hartin, MS, EFO, MIFireE, CFO

Everyday Concepts

Firefighters, like most everyone else, have a commonsense, everyday understanding of energy, heat and temperature. However, this everyday understanding is likely to be considerably different than the way these concepts are defined and used in science. Think about how heat and temperature are used on a day-to-day basis. On a sunny summer day, people are likely to say that it is hot because they feel hot or because the thermometer indicates a temperature is high. This may lead people to believe that temperature is a measure of hotness or heat. On the other hand, scientists view these concepts considerably differently!

So what! What difference does it make if we use our commonsense, everyday understanding of energy, heat, and temperature in our effort to make sense of fire dynamics? Why is this important?

If you are going to take a trip, it is useful to understand the concept of distance and have some type of units (e.g., kilometers or miles) to describe how far away your destination is. When describing a building, firefighters indicate the number of stories and dimensions (e.g., meters or feet). Having a good grasp of the concepts of energy, heat and temperature provides a way to describe the fire potential of different types of fuel, the size of a fire in terms of energy and power, and the thermal environment encountered by firefighters.

Take a minute and think about how you would define energy, heat, and temperature. Write your ideas down on a piece of paper so you can come back to them later. Don’t worry about the textbook definition, just write down what you think these words mean. After reading the rest of this post, come back to your notes and see how your understanding of energy, heat, and temperature has changed.

Energy, Heat, and Temperature in Firefighting

For many years, firefighters in the United States learned about British thermal units (Btu) as a measure of energy. A British thermal unit is the amount of energy required to raise the temperature of 1 pound of water (at 60^o Fahrenheit (F)) 1^o F. Firefighters often can state a reasonable approximation of this definition and the Btu seems to be a fairly simple unit of measure with direct applicability in the firefighting context.

“Before an observer can formulate and assent to an observation statement, he or she must be in possession of the appropriate conceptual framework and a knowledge of how to appropriately apply it” (Chalmers, 1999, p. 11). It is one thing to recognize a definition, but it is another thing entirely to be able to use this information in a broader context and make sense of things! For example a young child may be able to identify a red apple, but may not have a good understanding of what makes this fruit an apple (as opposed to a pear) or how a red apple and a green apple can both be apples. Developing an understanding of the fundamental scientific concepts that underlie fire dynamics and firefighting is much the same. Knowledge and understanding must extend beyond simple recognition of, or the ability to restate definitions and concepts presented in a text of lecture.

Thermodynamics

Thermodynamics is a branch of physics that describes processes that involve changes in temperature, transformation of energy, and the relationships between heat and work. Fire and firefighting also involves changes in temperature, transformation of energy, heat and work. “Thermodynamics, like much of the rest of science, takes terms with an everyday meaning and sharpens them – some would say, hijacks them – so that they take on an exact unambiguous meaning” (Atkins, 2007, p. 3).

Thermodynamics deals with systems. A thermodynamic system is one that interacts and exchanges energy with the area around it. A system could be as simple as a block of metal or as complex as a compartment fire. Outside the system are its surroundings. The system and its surroundings comprise the universe.

While in general terms the universe includes everything, we will generally look at things on a smaller scale. For example we might consider a burning fuel package as the system and the compartment as the surroundings. On a larger scale we might consider the building containing the fire as the system and the exterior environment as the surroundings.

Figure 1. Thermodynamic Systems

Thermodynamic systems can be classified on the basis of their interaction with the surroundings.

• Isolated systems do not exchange energy or matter with their environment.
• Closed systems exchange energy but not matter with their environment.
• Open systems exchange energy and matter with their environment. A boundary allowing matter exchange is called permeable.

Laws of Thermodynamics: These laws summarize the properties of energy and its transformation from one form to another. Numbered from zero to three, these laws are both simple and extremely complex. This series of posts examines the laws of thermodynamics in the context of fires and firefighting to move from theoretical to practical application.

Energy

Energy is a fundamental concept in physical science, but is difficult to define in a way that is meaningful on an everyday basis. Energy is the ability to do mechanical work or transfer thermal energy from one object to another. Energy can only be measured on the basis of its effects. There are basically two kinds of energy, kinetic and potential. Kinetic energy is associated with motion of an object and potential energy is that which is stored and may be released at a later time.

There are a number of different forms of energy; mechanical, chemical, electrical, radiant, and thermal. However, each has the ability to be transformed into work, which is force applied to an object, causing it to be displaced. In thinking about energy and work it is important to keep two things in mind:

• Energy is the capacity to do work.
• Work involves force causing movement in the direction of that force.

If the force does not influence movement in the direction of the force, no work was done.

Newtons (named after Isaac Newton) are the standard international (SI) unit for force. A Newton is the amount of force required to give a mass of one kilogram an acceleration of one meter per second squared. However, it may be easier to visualize force in terms of weight. In our everyday environment, weight is the force exerted as a result of our mass and the effects of gravity. For example, a kilogram (which is a unit of mass) exerts a downward force of 10 Newtons (or 2.2 pounds). To make things more complicated, kilograms are used in everyday language to express weight (rather than Newtons). This is because on earth, weight and mass are directly proportional.

The SI unit for energy (capacity to do work) is the Joule. A Joule is a force of one Newton causing displacement of an object a distance of one meter. For example, approximately one Joule of energy is required to lift a small apple (which weighs one Newton (or 0.22 pounds) a distance of 1 meter. In that energy is the capacity to do work, the Joule is also used to measure energy (regardless of its form).

While mechanical energy may be of interest to firefighters, what does this have to do with thermal energy and fire behavior? One really big puzzle is how Joules which are defined in terms of mechanical energy can be used to measure thermal energy? This is a really good question, but several more scientific concepts are needed in order to make sense of the answer.

Substances have potential chemical energy based on the bonds within and between their atoms and molecules. Formation, breaking, or rearrangement of these chemical bonds results in transfer of energy into or out of the substance. For example, in combustion the reaction of an oxidizer and fuel results in transformation of chemical potential energy into thermal and radiant kinetic energy. Thermal energy is molecular kinetic energy resulting from molecules moving around in random directions as well as molecular rotation and vibration. Radiant energy is comprised of electromagnetic waves in the infrared region of the electromagnetic spectrum although some is in the visible region. The term thermal radiation distinguishes this form of electromagnetic radiation from other forms such as radio waves and ionizing radiation

First Law of Thermodynamics: Energy cannot be created nor destroyed only transformed from one form to another. For example, in combustion the chemical reaction between oxygen and fuel results in transformation of chemical energy to thermal and radiant energy. However, the total amount of energy remains the same.

Temperature

Temperature is a measure of the average kinetic energy. Temperature of any substance, whether solid, liquid, or gas, is directly related to all motion (kinetic energy) of its molecules. This is especially important for liquids and solids because the kinetic energy of these substances is almost entirely vibrational and rotational. All molecules above a temperature of absolute zero (the temperature at which molecular motion stops) are in a continual state of motion and possess kinetic energy.

The Kelvin is the standard international unit for temperature. In this scale, temperature is measured in Kelvins (K), not degrees (as with the Celsius and Fahrenheit scales). While the least common in everyday use, the Kelvin thermodynamic temperature scale is important in understanding thermal energy, temperature, and heat. With the Kelvin scale, 0 K is absolute zero, the theoretical absence of all thermal energy.

While the Kelvin is the standard international unit for temperature, the Celsius scale is commonly used as both an everyday (outside the United States) and scientific measure of temperature. The degree Celsius (^o C) is the same increment of measure as the Kelvin, the difference between these two scales is the zero point on the scale. With the Celsius scale 0^o C is the freezing point of water (273.15 K) while as previously noted 0 K (-273.16^o C) is absolute zero.

In the United States, the Fahrenheit scale is commonly used to measure temperature on an everyday basis. Unlike the Celsius scale where the difference between the freezing and boiling points of water is 100^o, the Fahrenheit scale places the freezing point at 32^o and boiling point at 212^o, a difference of 180^o.

Figure 2. Common Temperature Scales

Note: Equivalent temperatures have been rounded to the closest whole unit (i.e., degree, kelvin).

The Kelvin temperature scale is used in scientific work involving thermodynamics, because this scale starts at absolute zero (the point at which a substance has no thermal energy). This means that temperature in Kelvins is a measure of the absolute temperature. Use of an absolute temperature scale allows expression of physical laws and mathematical formulas more simply.

For example, 100^o C is not twice as high a temperature as 50^o C (even though at first glance it appears that it is). This becomes clear when using the Kelvin scale. A temperature of 50^o C is 323.15 K while 100^o C is 373.15 K, an increase of just over 13% in absolute temperature.

Third Law of Thermodynamics: In the complete absence of molecular kinetic energy, the temperature of a substance would be absolute zero. Absolute is 0 K or -273.15° C.

Measuring Energy

As previously discussed, the SI unit of measure for energy is the Joule (J). While defined in terms of mechanical work, the joule is used for all forms of energy. In the standard international system of units, prefixes such as kilo (thousand) and mega (million) are used to provide incrementally larger units of measure. In the case of energy, a kilojoule (kJ) would be a thousand joules and a megajoule (MJ) would be one million joules.

While not commonly used in scientific work, the American fire service has typically used the British thermal unit (Btu) as a measure of thermal energy. The Btu is defined in terms of the heating effect of energy transferred to water. In order to provide a simple explanation of the Joule as a unit of measure for thermal energy and allow a direct comparison to the Btu, Figure 3 describes the J in terms of energy transfer to water and provides a comparison to the Btu.

Figure 3. Joule and British Thermal Unit

* In this case, Ounces is a measure of volume not mass (or weight). Another confusing aspect of the traditional system of measure used in the United States!

As illustrated in Figure 3, addition of 4186 joule of energy to a kilogram of water raises its temperature (average internal kinetic energy) by one degree Celsius. Similarly, adding one British thermal unit of energy to a pound of water raises its temperature by one degree Fahrenheit. Directly comparing these two examples is a bit complex as the units of measure for both energy (J & Btu) and temperature (^o C & ^o F) are different.

Some properties of materials are independent of their mass, color would be one example. Other properties are dependent on mass. Weight, would be the most obvious, but other properties are also dependent on the mass of material present.

Figure 4. Energy and Temperature Simulation

Note: This illustration was adapted from a simulation in Energy: Thermal Energy, Heat and Temperature, a National Science Teachers Association knowledge object.

The example provided in Figure 4 examines the difference between temperature and thermal energy as related to mass. The container labeled A initially contains a specific mass of liquid with a temperature of 30^o C and a total thermal energy of 8 J. Liquid is moved from the container labeled A to the one labeled B. How does the temperature of the liquid and thermal energy in each container change as this transfer takes place? The temperature of the liquid remains the same regardless of the quantity in each of the containers. However, as the mass of liquid in each container changes, the thermal energy of the liquid in the container changes as well. Related to average thermal energy, temperature is independent of mass, while the total thermal energy relates directly to mass. Properties of materials fall into two categories. Extensive properties (like energy) are dependent on the quantity (mass) of material while intensive properties (like temperature) are not.

What’s Next?

The next post in this series will examine the concept of heat and the relationship between heat, energy, and temperature.

Ed Hartin, MS, EFO, MIFireE, CFO

References

Atkins, P. (2000). Four laws that drive the universe. Oxford, UK: Oxford University Press

Chalmers, A. (1999) What is this thing called science? (3^rd ed.). Indianapolis, IN: Hackett.

National Science Teachers Association (NSTA). (2006). Energy: Thermal energy, heat and temperature. Retrieved February 27, 2010 from http://www.nsta.org/store/product_detail.aspx?id=10.2505/7/SCB-EN.3.1

A Quick Review

As discussed in the previous posts in this series, military battle drills are an immediate response to enemy contact that requires fire and maneuver in order to succeed. Battle drills are initiated with minimal commands from the unit leader. Soldiers or marines execute preplanned, sequential actions in response to enemy contact (see Figure 1).

Figure 1. Battle Drill

Battle Drill Part 2 addressed the appropriate reaction of a team of firefighters on a primary hoseline when confronted with rapidly worsening fire conditions that are not readily controllable once they occur (e.g., flashover, wind driven fire conditions). As when a military unit is ambushed, the fire and maneuver of battle drill involves more than one weapon. This post will address the role and reaction of backup lines in the extreme fire behavior battle drill.

Backup Lines

Once a hoseline has been deployed for fire attack it is good practice to stretch a backup line. Klaene and Sanders (2008) observe that backup lines are needed to protect the crew on the initial attack line and to provide additional flow if needed (p. 216). Unfortunately, many firefighters see the backup line as simply another attack line and miss the first and primary function of this hoseline to protect crews on primary hoselines.

The first priority in fire attack operations is to get a hoseline in position to apply water effectively to the fire. To this end, hoselines are deployed in series (attack line first, then backup line) not in parallel, where both lines are attempting to advance and maneuver in the same space. The crew of the backup line can often assist in pulling up additional hose for the attack line (particularly when crews are lightly staffed). As illustrated in Figure 2, the backup line is positioned to protect the means of egress and if necessary support fire attack.

Figure 2. Attack and Backup Line Placement

Extreme Fire Behavior Battle Drill

As discussed in Battle Drill Part 2, the thermal insult experienced in an extreme fire behavior event is dependent on temperature (of gases and compartment linings) and flow of hot gases. The higher the temperature and faster the speed of gas flow, the higher the heat flux. Survival requires that crews on hoselines extinguish or block the flames, cool hot gases, and maneuver out of the flow path to a point of egress or area of safer refuge.

Crews engaged in fire attack or search are often first to encounter rapidly deteriorating fire conditions. Hose Handling and Nozzle Technique Drill 8 outlined the immediate actions that should be taken to support a tactical withdrawal under severe fire conditions. In these circumstances, the crew staffing the backup line has a critical role in supporting withdrawing crews.

Fire conditions that are beyond the capability of a single hoseline may be controlled by the higher flow rate from multiple lines. As noted by Klaene and Sanders (2008) one of the functions of backup lines is to provide additional flow if needed (p. 216). The attack line and backup line operating in a coordinated manner may be able to control fire conditions and allow continuation of fire attack. If this is the case, these lines should be reinforced by deployment of one or more additional backup lines.

If fire conditions cannot be controlled, and the attack line must be withdrawn while maintaining water application to protect the crew, the crew on the backup line can aid in withdrawal of attack and/or search hoselines. If the hoseline is not withdrawn as the firefighter on the nozzle retreats, the hose may kink or become exposed to flames (either of which may result in loss of water supply to the nozzle).

While the attack or search crew is likely to be first to encounter worsening fire conditions, this is not always the case. Depending on fire location and building configuration, fire spread may cut off the attack or search line from behind. In this situation, the backup line becomes the primary means of defense for operating crews.

Regardless of how deteriorating conditions develop, safe and effective tactical withdrawal requires a coordinated effort between interior crews and as soon as possible, report of conditions to Command and if necessary transmit a Mayday message.

Drill 9-Extreme Fire Behavior Battle Drill-The Backup Line: Key hose handling and nozzle techniques when faced with extreme fire behavior are the ability to apply long pulses of water fog or maintaining a continuous flow rate while maneuvering backwards. However, the backup line may initially need to advance to support fire attack, and then if necessary cover and support other crews as they withdraw.

Hose Handling & Nozzle Technique Drill 9 Instructional Plan

Skill in operation and maneuver of a single hoseline is a foundational firefighting skill. However, in the extreme fire behavior battle drill, coordinated operation of the attack and backup line is essential, making Hose Handling & Nozzle Technique Drill 9 an important step in skill development.

References

Klaene, B. & Sanders, R. (2008) Structural Firefighting Strategy and Tactics (2^nd ed.). Sudbury, MA: Jones & Bartlett.

A Quick Review

As discussed in the last post in this series, military battle drills are an immediate response to enemy contact that requires fire and maneuver in order to succeed. Battle drills are initiated with minimal commands from the unit leader. Soldiers or marines execute preplanned, sequential actions in response to enemy contact.

This post discusses application of the battle drill concept in training firefighters to react appropriately on contact with our enemy (the fire) which requires fire (application of water) and maneuver (movement to a safer location) in order to succeed.

Remember: The key elements of a battle drill are fire and maneuver! This requires the ability to operate and maintain control of the hoseline while moving backward.

Working Without a Hoseline

In the United States, it is common for some companies working on the fireground to operate inside burning buildings without a hoseline (particularly when performing search). While common, this practice places firefighters at considerable risk when faced with extreme fire behavior. Without a hoseline your only defense against rapid fire progress is recognition of developing conditions and immediate reaction to escape to a safer location (see video below); which is not always possible. In some cases, firefighters fail to recognize developing conditions or the speed with which conditions will change. In other cases, firefighters are unable to escape or take refuge outside the flow path of hot gases and flames quickly enough.

Cl

If your department’s operational doctrine includes companies working on the interior without a hoseline (or without being directly supported by a hoseline), it is essential that firefighters are trained to 1) recognize early indicators of potential for extreme fire behavior and 2) maintain a high level of awareness regarding locations which may provide an area of refuge. When confronted by rapidly worsening conditions, action to escape must be immediate and without hesitation.

Extreme Fire Behavior Battle Drill

Regardless of their assignment (e.g., fire attack, primary search), firefighters with a hoseline have a solid means of maintaining orientation, a defined primary escape route, and the ability to actively control the fire environment through application of water. However, as always, safe and effective operation in the fire environment is dependent on a solid size-up, dynamic risk assessment, maintenance of a high level of situational awareness, and proactively controlling the fire environment. The best way to deal with extreme fire behavior is to avoid it or prevent it from occurring. For more information on reading the fire and key fire behavior indicators related to potential for extreme fire behavior, see:

• How to Improve Your Skills
• Building Factors
• Building Factors Part 2
• Building Factors Part 3
• Smoke Indicators
• Smoke Indicators Part 2
• Air Track Indicators
• Air Track Indicators Part 2
• Heat Indicators
• Heat Indicators Part 2
• Heat Indicators Part 3
• Flame Indicators
• Flame Indicators Part 2
• Reading the Fire: Putting it all Together
• Incipient Stage Fires: Key Fire Behavior Indicators
• Growth Stage Fires: Key Fire Behavior Indicators
• Fully Developed Fires: Key Fire Behavior Indicators
• Decay Stage Fires: Key Fire Behavior Indicators

In situations where you were unable to recognize potential for extreme fire behavior or you have been unable to control the fire environment, immediate action is required!

This is my nozzle, there are many like it but this one is mine. My nozzle is my best friend. It is my life. I must master it as I master my life. Without me it is useless, without my nozzle I am useless.

I will use my nozzle effectively and efficiently to put water where it is needed. I will learn its weaknesses, its strengths, its parts, and its care. I will guard it against damage, keep it clean and ready. This I swear.

As stated in the first paragraph of this adaptation of the United States Marine Corps Riflemans’ Creed, Without my nozzle I am useless.

The extent of thermal insult experienced in an extreme fire behavior event is dependent on both radiant and convective heat flux. Total radiant heat flux is dependent on temperature (of gases and compartment linings) and flow of hot gases. The higher the temperature and faster the speed of gas flow, the higher the heat flux. These scientific concepts drive the key elements of the extreme fire behavior battle drill. Extinguish or block the flames, cool hot gases, and maneuver out of the flow path to a point of egress or area of safer refuge.

Drill 8-Extreme Fire Behavior Battle Drill: Key hose handling and nozzle techniques when faced with extreme fire behavior are the ability to apply long pulses of water fog or maintaining a continuous flow rate while maneuvering backwards. This requires a coordinated effort on the part of the nozzle operator, backup firefighter, and potentially other firefighters working on the hoseline or at the point of entry.

Hose Handling & Nozzle Technique Drill 8 Instructional Plan

While this drill focuses on single company operations, it is important to extend this training to include crews operating backup lines. The importance, function, and operation of the backup line will be the focus of the next post in this series.

Not all That is Learned is Taught

When training to operate in a hazardous environment, avoid the mindset that it’s only a drill. As often observed, you will play the way that you practice. Extreme stress can activate inappropriate routine responses. For example, a Swedish army officer suddenly stood up while his unit was under fire while engaged in peacekeeping efforts in Bosnia. When asked about this response, he explained that in training, he often stood up while leading exercises (Wallenius, Johansson, & Larsson, 2002).

“A simple set of skills , combined with an emphasis on actions requiring complex and gross motor muscle operations (as opposed to fine motor control), all extensively rehearsed, allows for extraordinary performance levels under stress” (Grossman, 2008, p. 38).

When developing skill in nozzle technique and hose handline, and in particular the critical skills required to effectively perform this extreme fire behavior battle drill, it is essential to maintain critical elements of context such as appropriate use of personal protective equipment, position, and technique.

Ed Hartin, MS, EFO, MIFireE, CFO

References

Grossman, D. (2008). On-combat: The psychology and physiology of deadly conflict in war and peace. Millstadt, IL: Warrior Science Publications.

Wallenius, C. Johansson, C. & Larsson, G. (2002). Reactions and performance of Swedish peacekeepers in life-threatening situations. International Peacekeeping, 9(1), 133-152.

The Problem

NIOSH has investigated a number of incidents in which firefighters trapped by rapid fire progress did not take appropriate survival action. Last September, I was reading NIOSH Report F2007-02, which outlined the circumstances surrounding the death of Firefighter Steven Solomon in Atlanta, Georgia. Firefighter Solomon was severely burned after being caught by rapid fire development while advancing an attack line in a vacant structure (see Figure 1).

Figure 1. Rapid Fire Development

Note: Atlanta Fire Department photo from NIOSH Report F2007-02

Firefighter Solomon was on the nozzle as the first arriving truck removed the plywood covering the front door and thick, black smoke came rolling out the top of the doorway. Firefighter Solomon and the crew of Engine 16 advanced the line into the building as the truck continued horizontal ventilation. After advancing a short distance, fire conditions quickly worsened and the crew attempted to back out, but collided with another company who was advancing a backup line. After exiting the building the crew of Engine 16 realized that Firefighter Solomon was still inside. Crews outside the door on Side A observed the silhouette of a firefighter running through the flames inside the building.

As I read the report, I asked myself how a firefighter on a hoseline that was just a short distance could have been killed by rapid fire development. The NIOSH report identified four contributing factors:

• Initial size-up not conducted.
• Failure to recognize the signs of an impending flashover/flameover.
• Inadequate communication on the fireground.
• Possibility of ventilation induced rapid fire progression.

While these factors likely contributed to Firefighter Solomon’s death, I still did not have a solid answer to my question of how a firefighter on a hoseline just a short distance inside the doorway could have died in this type of event.

Predictability

The best way to avoid being injured or killed in an extreme fire behavior event is to read the fire, anticipate likely fire behavior, and control your operating environment. A majority of our effort should be spent on mastering these skills.

There is no unpredictable fire behavior. Under the same conditions, a compartment fire will develop and behave consistently. However, conditions are not always the same! In addition, firefighters operate with limited information, imperfect skill in anticipating likely fire behavior, and often under pressure to take rapid action. When making decisions under pressure, in a complex and dynamic environment, and with limited information, potential for error increases.

Improved understanding of fire dynamics and development of a high level of skill reduces, but does not eliminate your risk of encountering extreme fire behavior. When this occurs it is essential that firefighters understand the fire behavior, their own reactions to stress, and have well practiced (to automaticity) responses to increase the chance of survival.

Training for Survival

What exactly are firefighter survival skills? Firefighters may encounter a number of life threatening problems while operating in the hazardous environment of as structure fire. Threats include breathing apparatus emergencies (e.g., malfunctions, running out of air), becoming disoriented, and being trapped by collapse or rapid fire progress.

A quick survey of survival skills training programs from around the United States shows a fair degree of consistency in curriculum content:

• Emergency Communications Procedures (Mayday, Radio Emergency Distress Button)
• Personal Alert Safety System (PASS) Activation
• Reorientation, Searching for an Exit & Following a Hoseline to Safety
• Air Conservation Techniques
• Assuming a Horizontal Position to Enhance Thermal Protection and Audibility of the PASS
• Escape to a Place of Refuge
• Use of Visual and Audible Signals (Flashlight, Tapping with a Tool)
• Reduced Profile Maneuvers to Escape Through Small Openings
• Emergency Window Egress (Ladder Bail, Rope Systems)

These techniques may provide useful in dealing with a number of the threats that may be encountered in a structure fire. Taking refuge in an uninvolved compartment (with the door closed) may buy time for firefighters to escape through a window. However, the other elements will have little impact on increasing survival potential when encountering extreme fire behavior phenomena.

What is the missing element in the typical survival skills curriculum? In some cases, firefighters are taught breathing techniques to control their respiratory rate and conserve air, but little emphasis is provided on the psychological and physiological effects of the stress encountered in life threatening situations. This is critical to survival regardless of the nature of the threat. When faced with extreme fire behavior, particularly wind driven flames, flashover, and flash fire, appropriate nozzle technique and immediate tactical withdrawal to a safer area is absolutely critical. However, most survival skills curriculums do not address these critical skills.

When was the last time you practiced withdrawing a hoseline while operating the nozzle in the context of offensive, interior firefighting operations?

Performance Under Stress

There has been little if any research has been done to identify factors influencing firefighters’ performance under the extreme stress of a life threatening situation. However, there has been considerable investigation in other domains, particularly in the military and law enforcement

Increased psychological and physiological arousal prepare the human body for action. As this occurs, the sympathetic nervous system increases heart rate and blood pressure to maximize the body’s physical capacity. However, extreme levels of stress can result in significant deterioration in performance.

In On-Combat: The Psychology and Physiology of Deadly Conflict in War and Peace, LT COL Dave Grossman (2008) identifies five levels of arousal designated Conditions White, Yellow, Red, Grey, and Black. While cautioning against fixing specific heart rate numbers (or other precise physiological measures) to these levels of arousal, heart rate can be used as an indicator (see Figure 2).

Figure 2. Effects of Hormonal or Fear Induced Increases in Heart Rate

Note. Adapted from On-Combat: The Psychology and Physiology of Deadly Conflict in War and Peace (p. 31), by Dave Grossman, 2008, Millstadt, IL: Warrior Science Publications Copyright 2008 by David A. Grossman.

When face with an immediately life threatening situation, the resulting stress can significantly impact an individual’s ability to respond appropriately. In addition to the physiological responses (e.g. increased heart rate, visual and auditory distortion) decreased cognitive processing may delay appropriate response or result in freezing, with the inability to act (Wallenius, Johansson, & Larsson, 2002).

Recently a colleague related the experience of a firefighter who had been trapped by a wind driven fire. The firefighter dropped to the floor, went into the fetal position, said goodby to his wife and children and thought he was dead. Fortunately, the firefighter was rescued, but this illustrates the potentially incapacitating effects of stress in life threatening situations.

What is the answer? Military research points to the need for a highly trained (to automaticity) response. Battle drills integrate these immediate individual actions in the context of small unit operations.

Battle Drill

In a military context, battle drills are an immediate response to enemy contact that requires fire and maneuver in order to succeed. Battle drills are initiated with minimal commands from the unit leader. Soldiers or marines execute preplanned, sequential actions in response to enemy contact.

The battle drill concept has direct applicability to training firefighters to react appropriately on contact with our enemy (the fire) which requires fire (application of water) and maneuver (movement to a safer location) in order to succeed.

Unless a barrier (such as a door) is available to block the flow of flames and hot gases towards the firefighters position, attempts to escape without protection from a hoseline are likely to fail as fire can spread far more quickly than you can move.

Remember: The key elements of a battle drill are fire and maneuver! This requires the ability to operate and maintain control of the hoseline while moving backward.

The next post in this series will return to hose and nozzle drills with development of a battle drill for response to rapid fire progression.

Ed Hartin, MS, EFO, MIFireE, CFO.

References

Grossman, D. (2008). On-combat: The psychology and physiology of deadly conflict in war and peace. Millstadt, IL: Warrior Science Publications.

Wallenius, C. Johansson, C. & Larsson, G. (2002). Reactions and performance of Swedish peacekeepers in life-threatening situations. International Peacekeeping, 9(1), 133-152.

At a formal dinner on 23 January 2010, Chief Ed Hartin was recognized as an honorary member of Company 1 “Germania” of the Valdivia, Chile Fire Department. In addition, he was awarded a commendation for supporting the ongoing professional development of the members of Company 1 “Germania” of the Valdivia, Chile Fire Department and encouraging them in their efforts to share their knowledge with Chile’s fire service.

Commendation for Support of Company 1 “Germania”

Left to Right: Teniente Juan Esteban Kunstmann, Chief Ed Hartin, Capitán Francisco Silva V.

On 24-27 January 2007, the Company 1 “Germania” of the Valdivia, Chile Fire Department hosted the first international fire service congress to be held in South America. Participants included over 150 firefighters and officers from Chile, Peru, Argentina, and the United States. The congress provided an opportunity to participate in both classroom and hands-on workshops on a wide range of fire service topics including fire behavior, ventilation, search, rapid intervention, technical rescue, and extrication. While topical areas were diverse, the congress had a substantive emphasis on compartment fire behavior with lectures presented by CFBT-US Chief Instructor Ed Hartin and Geraldo Crespo of Contraincendio in Buenos Aires, Argentina and practical training sessions conducted by Ed Hartin and Juan Esteban Kunstmann of the Valdivia Company 1 “Germania”.

Lecture Presentation

Lecture presentations by CFBT-US Chief Instructor Ed Hartin included (click on the links for a copies of the presentations):

• Fire Development and Flashover: Foundational Knowledge
• Extreme Fire Behavior: Understanding the Hazard
• 3D Firefighting: Controlling the Fire Environment
• Reading the Fire: B-SAHF
• Modern Buildings: Fires in the Built Environment
• Large Area Fires: Tactical Implications
• Fire and Smoke in Void Spaces: Hidden Hazards
• Live Fire Training as Simulation: The Role of Fidelity

CFBT practical skills sessions were held at the Valdivia Fire Department’s training center and focused on developing basic skill in nozzle technique and understanding fire development in a compartment.

This is My Nozzle! There are many like it, but this one is mine…

Center: Ed Hartin

Practicing Nozzle Techniques

Right: Teniente Juan Esteban Kunstmann

International Collaboration

Left to Right: Battalion Chief Danny Sheridan, FDNY and Capitán Giancarlo Passalacqua Cognoro, Lima, Pe?u Cuerpo General de Bomberos Voluntarios

Congratulations to the members of Company 1 “Germania” for their success with the first Congreso Internacional Fuego y Rescate! I look forward to working with these outstanding fire service professionals in their ongoing efforts to learn and share knowledge with the fire service throughout Chile, Latin America, and the World.

Ed Hartin, MS, EFO, MIFireE, CFO

Two recent events in Baltimore, Maryland and Gary, Indiana point to the criticality of recognizing key fire behavior indicators and understanding practical fire dynamics.

Five Firefighters Injured in Baltimore

Early on the morning of Friday, January 15, 2010, the Baltimore City Fire Department was dispatched to a residential fire Southeast Baltimore. First arriving companies observed a row house of ordinary construction with a large volume of smoke and flames issuing from the basement and extending to the first floor.

According to a department spokesperson, the first engine took a line through the front door to the rear kitchen area where crew had some trouble finding the basement stairs. Another engine company went to the rear with a line to the outside stairwell leading to the basement and was just starting down the stairs. The first truck vented some skylights on the roof as well as the front basement windows. As crews were attempting to access the fire, some type of transient extreme fire behavior resulted in flames blowing through the unit and out the front door, rear stairwell, second floor windows, and skylights. The firefighter from the first arriving truck assigned to the roof described the sound of a freight train coming through.

Five firefighters injured as a result of this explosive fire behavior phenomenon were transported to area hospitals. The officer of the first in engine company was admitted to the Bayview Burn Center, where he is listed in stable condition

Find more videos like this on firevideo.net

What Happened?

As always when a video of an incident involving extreme fire behavior is posted to the web, there is ongoing debate about what happened. Was it a backdraft? Was it a flashover? An interesting debate, but the value is not so much in being “right”, but in understanding how these phenomena occur, what might have happened in this incident, key indicators that may (or may not) be visible in the video, and most importantly how to prevent this from happening to us and the firefighters that we work with!

Flashover: sudden transition to fully developed fire. This phenomenon involves a rapid transition to a state of total surface involvement of all combustible material within the compartment.

Given adequate fuel and ventilation, a compartment fire may reach flashover as it develops from the growth to fully developed stage. However, when fire development is limited by the ventilation profile of the compartment, changes in ventilation will directly influence fire behavior.

For many years firefighters have been taught that ventilation reduces the potential for flashover. However, when a fire is ventilation controlled, heat release rate is limited by the available oxygen. Under these conditions; increasing air supply by creating opening results in increased heat release rate. This increased heat release rate may result in flashover.

If a fire is sufficiently ventilation controlled and a high concentration of excess pyrolizate and unburned flammable products of combustion accumulate in a compartment, the outcome of increased ventilation may be different.

Backdraft: Deflagration of unburned pyrolyzate and combustion products following introduction of air to a ventilation controlled compartment fire and ignition of the fuel/air mixture. This deflagration results in a rapid increase in pressure within the compartment and extension of flaming combustion through compartment openings. Occurrence of this phenomenon requires an atmosphere in which the fuel concentration is too high to deflagrate without introduction of additional oxygen.

As introduced in Extreme Fire Behavior: An Organizational Scheme, extreme fire behavior phenomena can be classified on the basis of outcome and conditions (see Figure 1)

Figure 1. Extreme Fire Behavior Classification.

Use of this approach may aid in making sense of what may have occurred in the Baltimore incident. But, it is often difficult to classify extreme fire behavior phenomena into discrete, black and white categories. What is the dividing line between a ventilation induced flashover and a backdraft. One key difference may be the speed with which heat release rate increases, but where is the dividing line (see Figure 2)?

Figure 2. The Gray Area.

Keep in mind that while being right is great, it is more important to work through the process of figuring things out to improve your understanding.

Near Miss in Gary

Monday morning January 18, 2010 firefighters in Gary, Indiana were operating at a residential fire at 24^th and Massachusetts when they experienced a near miss involving rapid fire progression. Have a look at video of this incident and give some thought to what influenced fire behavior. Also look at the similarities and differences between the extreme fire behavior that occurred in the Baltimore and Gary incidents.

Back on Task!

I have been extremely busy working on a project for the National Institute for Occupational Safety and Health and preparing for the International Fire & Rescue Congress in Valdivia, Chile. Next week’s post will provide a quick update on training conducted at the Congress.

After returning from Chile, I will be back on task with examination of the concept of battle drills to develop effective reaction to worsening fire conditions while operating in an offensive mode.

Ed Hartin, MS, EFO, MIFireE, CFO