Posts Tagged ‘Tactical Ventilation’

My last post examined National Institute for Standards and Technology (NIST) tests of wind control devices to mitigate hazards presented during wind driven compartment fires (Fire Fighting Tactics Under Wind Driven Conditions). Heat release rate (HRR)� data from Experiment 1 (baseline test with no wind) and Experiment 3 (wind driven) illustrates the dramatic influence of increasing ventilation to a ventilation controlled fire and even more dramatic impact when increased ventilation is coupled with wind (see Figure 1). This post posed several questions related to the HRR data from these experiments.

Figure 1. Heat Release Rates in Experiments 1 (Baseline) and 3 (Wind Driven)

Note: Adapted from Firefighting Tactics Under Wind Driven Conditions.

Questions

Examine the HRR curves in Figure 1 and answer the following questions:

• What effect did deployment of the wind control device have on HRR and why did this change occur so quickly?
• How did HRR change when the wind control device was removed and why was this change different from when the window was vented?
• What factors might influence the extent to which HRR changes when ventilation is increased to a compartment fire in a ventilation controlled burning regime?

Answers: Application of the wind control device rapidly decreased heat release rate from approximately 19 MW to 5 MW. With the window covered, the fire lacked sufficient oxygen to maintain the higher rate of HRR. As oxygen was quickly consumed (and oxygen concentration was decreased) by the large volume of flaming combustion in the compartments, heat release rate was rapidly reduced.

As with the change in HRR when the window was vented, removal of the wind control device resulted in an extremely rapid increase in HRR as additional oxygen was provided to the ventilation controlled fire inside the structure. In this case, the increase was even more significant with the peak HRR reaching approximately 32 MW. Examination of the oxygen concentration curve provides a hint of why this might have been the case (see Figure 2). The oxygen concentration was higher before the window was vented than when the wind control device was removed. The more rapid and greater rise in HRR is likely a result of the extent to which the fire was ventilation controlled and the available concentration of gas phase fuel. After the wind control device was removed, note that the oxygen concentration increased sharply (which relates to the rapid increase in HRR), followed by a rapid decrease as ventilation was inadequate to maintain that rate of combustion.

Figure 2. Oxygen Concentration in the Bedroom

Note: Adapted from Firefighting Tactics Under Wind Driven Conditions.

Practical Application

The results of the NIST research are extremely interesting to students of fire behavior. However, it is essential that we be able to transform this information into knowledge that has practical application. This gives rise to three fundamental questions:

• How do changes in ventilation influence fire behavior? Note that this is always a concern, not just under wind conditions!
• What impact will wind have if the ventilation profile changes?
• What tactical options will be effective in mitigating hazards presented by extreme fire behavior under wind driven conditions?

It is important to consider air track and the flow path from inlet to exhaust opening and the potential consequences of introducing air under pressure without (or with an inadequate) exhaust opening. Both can have severe consequences!

Tactical Problem

One good way to wrestle with the influence of wind on compartment fire behavior is to put it into a realistic context. In the following tactical problem you will be presented with an incident scenario and a series of questions. Apply what you have learned and consider how you would approach this incident.

Resources: You have what you have! Use your normal apparatus assignment and staffing levels when working through this tactical problem.

Weather Information: Conditions are clear with a temperature of 20^o C (68^o F) and a 24 kph (15 mph) wind out of the Northwest.

Dispatch Information: You have been dispatched to a residential fire at 0700 on a Sunday morning. The caller reported seeing smoke from a house at 1237 Lakeview Drive. After companies go enroute, the dispatcher provides an update that she is receiving multiple calls for a fire at this location.

Conditions on Arrival: Approaching the incident location you observe a moderate volume of medium gray smoke from a wood frame, single family dwelling (most structures in this area are of lightweight construction). Smoke is blowing towards the A/D corner of the structure. As illustrated in Figure 3, smoke is visible from the front entry (window and door) of the house and it appears that smoke is showing from Side C as well. On closer examination, you observe that the upper level of the windows on Side A are stained with condensed pyrolysis products, but are intact.

Figure 3. View from Side A

360^o Reconnaissance: Moving down Side B, you observe a substantial body of fire in the center of the house. Smoke is pushing from around several sliding glass doors on Side B (see Figure 4) and flames are visible in the upper layer. The glass in the sliding doors is blackened and cracked, but is still intact. Smoke is also visible from around a large window on Side B Floor 2. Smoke discharge on Side B is swirling and being pushed up over the roof by the wind.

Figure 4. View from the BC Corner

Proceeding around the structure to Sides C and D, you observe a small amount of smoke pushing out from around the windows on Side D.

Questions: The first set of questions deals with size-up and development of an initial plan of action.

• What B-SAHF indicators do you observe in Figures 2 and 3?
• What stage(s) of fire development is (are) likely to exist in the structure?
• What burning regime is the fire in?
• How is the fire likely to develop in the time that it will take to develop and implement your incident action plan?
• Would you have given orders to your crew (or would they have taken pre-planned standard actions) based on your observation of conditions on Side A (Figure 1)? If so what would have been done? Why?
• Would your action plan have changed based on your observations from the B/C corner? What would you do differently? Why?
• What is your action plan at this point? Do you have sufficient resources? What orders would you give the first alarm companies? What actions would you have your crew take? Why?

Your action plan is dependent on size-up and assessment of incident conditions.� Variation in conditions may result in a change in the priority or sequence of tactical action. Would your action plan have been different if the dispatcher had indicated that the caller was trapped in the house? If it would have, what would you have done differently? Why?

Things to Think About

This tactical problem presents a number of challenges. Click on the link to examine the Floor Plan and then consider the following questions:

• What conditions would firefighters have encountered if they made entry through the door on Side A (front door)? Why?
• How would these conditions have changed if glass in one or more of the sliding doors on Side B had failed after firefighters had made entry? Why?
• What conditions would have resulted if the glass in one or more of the sliding doors on Side B had failed and the door on Side A was not open? Why?
• What options for fire attack and tactical ventilation would have been effective in this situation? Would your choice fire attack and tactical ventilation location, sequence, and coordination have varied based on the report of occupants? Why?
• How did your knowledge of the results of the NIST tests on wind driven fires impact your understanding of this incident? How did this understanding influence your tactical decision-making?

It is important to practice strategic and tactical decision-making. However, it is also important to think about how and why we make these decisions. This meta-learning (learning about our learning) has a significant impact on our professional development and ability to learn our craft.

Remember the Past

As discussed in previous posts, it is important to honor the sacrifices of firefighters who have died in the line of duty and not lose lessons learned as time passes. The following narratives were taken from the United States Fire Administration (USFA) reports on Firefighter Line of Duty Deaths (1994 and 2004).

March 29, 1994
Captain John Drennan, 49, Career
Firefighter James Young, 31, Career
Firefighter Christopher Seidenburg, 25, Career
Fire Department of the City of New York, New York

On March 29, three firefighters trapped in the stairwell of a brownstone were burned when they were enveloped in fire while attempting to force their way through a heavy steel door to a second floor apartment. Captain John Drennan, Firefighter James Young, and Firefighter Christopher Seidenburg of the New York City Fire Department were conducting a search when the hot air and toxic gases that collected in the stairwell erupted into flames as other fire crews forced entry into the first floor apartment where the fire had originated. The fire exhibited characteristics of both a backdraft and a flashover. Firefighter Young, in the bottom position on the stairs, was burned and died at the scene. Firefighter Seidenberg and Captain Drennan were rescued by other firefighters. They were transported to a burn unit with third and fourth degree burns over 50 of their bodies. Seidenburg died the next day. Drennan passed away several weeks later. The fire cause was determined to be a plastic bag left by the residents on top of the stove of the floor apartment.

For additional information on this incident see:

Bukowski, R. (1996). Modeling a backdraft: The 62 Watts Street incident. Retrieved March 14, 2009 from http://fire.nist.gov/bfrlpubs/fire96/PDF/f96024.pdf

March 21, 2003 – 0850
Firefighter Oscar “Ozzie” Armstrong, III, Age 25, Career
Cincinnati Fire Department, Ohio

Firefighter Armstrong and the members of his fire company responded to the report of a fire in a two-story residence. The first fire department unit on the scene, a command officer, reported a working fire.

Firefighter Armstrong assisted with the deployment of a 350-foot, 1-3/4-inch handline to the front door of the residence. Once the door was forced open, firefighters advanced to the interior. The handline was dry as firefighters advanced; the hose had become tangled in a bush.

As the line was straightened and water began to flow to the nozzle, a flashover occurred. The firefighters on the handline left the building and were assisted by other firefighters on the front porch of the residence. All firefighters were ordered from the building, air horns were sounded to signal a move from offensive to defensive operations.

Several firefighters saw Firefighter Armstrong trapped in the interior by rapid fire progress. These firefighters advanced handlines to the interior and removed Firefighter Armstrong. A rapid intervention team assisted with the rescue.

Firefighter Armstrong was severely burned. He was transported by fire department ambulance to the hos�pital where he later died.

The origin of the fire was determined to be a pan of oil on the stove.

For additional information on this incident see:

National Institute for Occupational Safety and Health (NIOSH). (2005). Death in the line of duty report F2003-12. Retrieved March 14, 2009 from http://www.cdc.gov/niosh/fire/pdfs/face200312.pdf

Laidlaw Investigation Committee. (2004)Line of duty death enhanced report Oscar Armstrong III March 21, 2004. Retrieved March 14, 2009� from http://www.iafflocal48.org/pdfs/enhancedloddfinal.pdf

Ed Hartin, MS, EFO, MIFireE, CFO

References

Madrzykowski, D. & Kerber, S. (2009). Fire fighting tactics under wind driven conditions. Retrieved (in four parts) February 28, 2009 from http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part1.pdf; http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part2.pdf;http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part3.pdf;http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part4.pdf.

United States Fire Administration (USFA). (1995) Analysis report on firefighter fatalities in the United States in 1994. Retrieved March 14, 2009 from http://www.usfa.dhs.gov/downloads/pdf/publications/ff_fat94.pdf

United States Fire Administration (USFA). (2005). Frefighter fatalities in the United States in 2004. Retrieved March 14, 2009 from http://www.usfa.dhs.gov/downloads/pdf/publications/fa-299.pdf

My last post asked a number of questions focused on results of baseline compartment fire tests conducted by the National Institute for Standards and Technology (NIST) as part of a research project on� Firefighting Tactics Under Wind Driven Conditions.� This post looks at the answers to these questions and continues with an examination of NIST’s experiments in the application of wind control devices for anti-ventilation.

Questions

Generally being practically focused people, firefighters do not generally dig into research reports. However, the information on the baseline test conducted by NIST raised several interesting questions that have direct impact on safe and effective firefighting operations. First consider possible answers to the questions and then why this information is so important (the “So what?”!).

Figure 1. Heat Release Rate Comparison

Note: Adapted from Firefighting Tactics Under Wind Driven Conditions.

Heat Release Rate (HRR) Questions: Examine the heat release rate curves in Figure 1 and answer the following questions:

• Why are these two HRR curves different shapes?
• In each of these two cases, what might have influenced the rate of change (increase or decrease in HRR) and peak HRR?
• What observations can you make about conditions inside the test structure and heat release rate (in particular, compare the HRR and conditions at approximately 250 and 350 seconds)?

Answers: The HRR test for the bed and waste container was conducted under fuel controlled conditions (oxygen supply was not restricted). The higher HRR in the compartment fire experiment results from increased fuel load (e.g., additional furniture, carpet). After reaching its peak, HRR in the compartment fire drops off slowly as the fire becomes ventilation controlled and the fire continues in a relatively steady state of combustion (limited by the air supplied through the lower portion of the bedroom window)

The rate of change in heat release rate under fuel controlled conditions is dependent on the characteristics and configuration of the fuel. �However, in the case of the compartment fire test, the rate of change is also impacted by limited ventilation. As illustrated in the compartment fire curve, the fire quickly became ventilation controlled and HRR rose slowly until the window failed and was fully cleared by researchers.

At 250 seconds (when the window was vented) HRR rose extremely rapidly as the fire in the bedroom rapidly transitioned from the growth through flashover to fully developed stage. At 350 seconds the fire had again become ventilation controlled and was burning in a relatively steady state limited by the available oxygen.

The fully developed fire in the bedroom also became ventilation controlled due to limited ventilation openings, resulting in HRR leveling off with relatively steady state combustion based on the available oxygen.

Figure 2. Bedroom Temperature

Note: Adapted from Firefighting Tactics Under Wind Driven Conditions.

Temperature Questions: Examine the temperature curves in Figure 2 and answer the following questions:

• What can you determine from the temperature curves from ignition until approximately 250 seconds?
• How does temperature change at approximately 250 seconds? Why did this change occur and how does this relate to the data presented in the HRR curve for Experiment 1 (Figure 1)?
• What happens to the temperature at the upper, mid, and lower levels after around 275 seconds? Why does this happen?

Answers: Temperature at the upper levels of the compartment increased much more quickly than at the lower level and conditions in the compartment remained thermally stratified until the ceiling temperature exceeded 600^o C. At approximately 250 seconds, the compartment flashed over resulting in a rapid increase in temperature at mid and lower levels. This change correlates with the rapid increase in HRR occurring at approximately 250 seconds in Figure 1. Turbulent, ventilation controlled combustion resulted in a loss of thermal layering with temperatures in excess of 600^o C from ceiling to floor. At around 275 seconds.

Figure 3. Total Hydrocarbons at the Upper Level

Note: Adapted from Firefighting Tactics Under Wind Driven Conditions.

Total Hydrocarbons (THC) Questions: Examine the THC curves in Figure 3 and answer the following questions:

• Why did the THC concentration in the living room rise to a higher level than in the bedroom?
• Why didn’t the gas phase fuel in the living room burn?
• How did the concentration of THC in the bedroom reach approximately 4%? Why wasn’t this gas phase fuel consumed by the fire?

Answers: Oxygen entering the compartments through the window was being used by combustion occurring in the bedroom. Low oxygen concentration limited combustion in the living room and allowed accumulation of a higher concentration of unburned fuel. While the oxygen concentration in the bedroom was higher, the fire was still ventilation controlled and not all of the gas phase fuel was able to burn inside this compartment.

So What?

What do the answers to the preceding questions mean to a company crawling down a dark, smoky hallway with a hoseline or making a ventilation opening at a window or on the roof?

Emergency incidents do not generally occur in buildings equipped with thermocouples, heat flux gages, gas monitoring equipment, and pre-placed video and thermal imaging cameras. Understanding the likely sequence of fire development and influencing factors is critical to not being surprised by fire behavior phenomena. These tests clearly illustrated how burning regime (fuel or ventilation controlled) impacts fire development and how changes in ventilation can influence fire behavior. The total hydrocarbon concentration and ventilation controlled combustion in the living room would present a significant threat in an emergency incident. How might conditions change if the fire in the bedroom was controlled and oxygen concentration began to increase? Ignition of the gas phase fuel in this compartment could present a significant threat (see Fire Gas Ignitions) or even prove deadly (future posts will examine the deaths of a captain and engineer in a fire gas ignition in California).

Anti-Ventilation

For years firefighters throughout the United States have been taught that ventilation is “the planned and systematic removal of heat, smoke, and fire gases, and their replacement with fresh air”. This is not entirely true! Ventilation is simply the exchange of the atmosphere inside a compartment or building with that which is outside. This process goes on all the time. What we have thought of as ventilation, is actually tactical ventilation. This term was coined a number of years ago by my friend and colleague Paul Grimwood (London Fire Brigade, retired). It is essential to recognize that there are two sides to the ventilation equation, one is removal of the hot smoke and fire gases and the other is introduction of air. Increased ventilation can improve tenability of the interior environment, but under ventilation controlled conditions will result in increased heat release rate.

Another tactic change the ventilation profile and influence fire behavior and conditions inside the building is to confine the smoke and fire gases and limit introduction of air (oxygen) to the fire. Firefighters in the United States often think of this as confinement, but I prefer the English translation of the Swedish tactic, anti-ventilation. This is the planned and systematic confinement of heat, smoke, and fire gases and exclusion of fresh air. The concept of anti-ventilation is easily demonstrated by limiting the air inlet during a doll’s house demonstration (see Figure 4). Closing the inlet dramatically reduces heat release rate and if sustained, can result in extinguishment.

Figure 4. Anti-Ventilation in a Doll’s House Demonstration

For a more detailed discussion of the relationship between ventilation and heat release rate see my earlier post on Fuel and Ventilation.

Air Track and Influence of Wind

Air track (movement of smoke and air under fire conditions) is influenced by differences in density between hot smoke and cooler air and the location of ventilation openings. However, wind is an often unrecognized influence on compartment fire behavior. Wind direction and speed can influence movement of smoke, but more importantly it can have a dramatic influence on introduction of air to the fire.

While the comparison is not perfect, the effects of wind on a compartment fire can be similar to placing a supercharger on an internal combustion engine (see Figure 5). Both dramatically increase power (energy released per unit of time).

Figure 5. Influence of Wind

NIST Wind Control Device Tests

As discussed in Wind Driven Fires, the effects of wind on compartment fire behavior can present a significant threat to firefighters and has resulted in a substantive number of line-of-duty deaths. In their investigation of potential tactical options for dealing with wind driven fires, NIST researchers examined the use of wind control devices (WCD) to limit introduction of air through building openings (specifically windows in the fire compartment in a high-rise building) as illustrated in Figure 6.

Figure 6. Small Wind Control Device

Note: Photo from Firefighting Tactics Under Wind Driven Conditions.

Questions

Give some thought to how wind can influence compartment fire behavior and how a wind control device might mitigate that influence.

• How would a strong wind applied to an opening (such as the bedroom window in the NIST tests) influence fire behavior in the compartment of origin and other compartments in the structure?
• How would a wind control device deployed as illustrated in Figure 5 influence fire behavior?
• While the wind control device illustrated in Figure 5 was developed for use in high-rise buildings, what applications can you envision in a low-rise structure?
• What other anti-ventilation tactics could be used to deal with wind driven fires in the low-rise environment?

The Story Continues…

My next post will address the answers to these questions (please feel free to post your thoughts) and examine the results of NIST’s tests on the use of wind control devices for anti-ventilation.

References

Madrzykowski, D. & Kerber, S. (2009). Fire Fighting Tactics Under Wind Driven Conditions. Retrieved (in four parts) February 28, 2009 from http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part1.pdf; http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part2.pdf;http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part3.pdf;http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part4.pdf.

Ed Hartin, MS, EFO, MIFireE, CFO

Weather, Topography, and Fuel

In S-190 Introduction to Wildland Fire Behavior, firefighters learn that weather, topography, and fuel and the principal factors influencing fire behavior in the wildland environment. How might this important concept apply when dealing with fires in the built environment? Factors influencing compartment fire behavior have a strong parallel to those in the wildland environment. Principal influences on compartment fire behavior include fuel, configuration (of the compartment and building), and ventilation.

Wind Driven Compartment Fires

As buildings are designed to minimize the influence of weather on their contents and occupants, weather is not generally considered a major factor in compartment fires. However, this is not always the case. As wildland firefighters recognize, wind can be a major influence on fire behavior and strong winds present a significant threat of extreme fire behavior.

Under fire conditions, unplanned ventilation involves all changes influencing exhaust of smoke, air intake, and movement of smoke within the building that are not part of the incident action plan. These changes may result from the actions of exiting building occupants, fire effects on the building (e.g., failure of window glass), or a wide range of other factors.

Changes in ventilation can increase fire growth and hot smoke throughout the building. Failure of a window in the fire compartment in the presence of wind conditions can result in a significant and rapid increase in heat release. If this is combined with open doors to corridors, unprotected stairwells, and other compartments, wind driven fire conditions have frequently resulted in firefighter injuries and fatalities (see Additional Reading).

NIST Research on Wind Driven Fires

From November 2007 to January 2008, the National Institute of Standards and Technology conducted a series of experiments examining firefighting tactics dealing with wind driven compartment fires. The primary focus of this research was on the dynamics of fire growth and intensity and the influence of ventilation and fire control strategies under wind driven fire conditions. The results of these experiments are presented in Fire Fighting Tactics Under Wind Driven Conditions, published by The Fire Protection Research Foundation.

Tests conducted at NIST’s Large Fire Test Facility (see Figure 1) included establishment of baseline heat release data for the fuels (bed, chairs, sofa, etc), full scale fire tests under varied conditions (e.g., no wind, wind), and experiments involving control of the inlet opening and varied methods of external water application.

Figure 1. NIST Large Fire Test Facility

Note: Photo adapted from Firefighting Tactics Under Wind Driven Conditions.

The objectives of this study were:

• To understand the impact of wind on a structure fire fueled with residential furnishings in terms of temperature, heat flux, heat release rate, and gas concentrations
• To quantify the impact of several novel firefighting tactics on a wind driven structure fire
• Improve firefighter safety

After conducting a series of tests to determine the heat release rate characteristics of the fuels to be used for the full scale tests, NIST conducted eight full scale experiments to examine the impact of wind on fire spread through the multi-room test structure (see Figure 2) and examine the influence of anti-ventilation using wind control devices and the impact of external water application.

Multi-Room Test Structure

All tests were conducted under the 9 m (30′) x 12 m (40′) oxygen consumption calorimetry hood at the NIST Large Fire Test Facility. The test structure was comprised of three compartments; Bedroom, Target Room (used to assess tenability in a compartment adjacent to the ventilation flow), and Living Room, along with an interconnecting hallway and exterior hallways. A large mechanical fan was positioned 7.9 m (26′) away from the window in the bedroom of the test structure (see Figure 2) to provide consistent wind conditions for the experiments.

Figure 2. Configuration of the Multi-Room Test Structure

Note: Adapted from Firefighting Tactics Under Wind Driven Conditions.

The structure was framed with steel studs and wood truss joist I-beams (TJIs) used to support the ceiling. The interior of the compartments were lined with three layers of 13 mm (1/2″) gypsum board. Multiple layers of gypsum board were used to provide the durability required for repetitive experiments (the inner layer was replaced and repairs made to other layers as needed between experiments).

Used furnishings were purchased from a hotel liquidator to obtain 10 sets of similar furniture to use in the heat release rate and full-scale, multi-compartment experiments. Fuel used in the tests included furniture, nylon carpet, and polyurethane carpet padding (the position major furniture items are illustrated in Figures 2 and 3).� Fuel load was 348.69 kg (768.73 lbs) in the bedroom, 21.5 kg (47.40 lbs) in the hallway, and 217.6 kg (479.73 lbs) in the living room (no contents were placed in the target room).

Figure 3. Bedroom and Living Room Fuel Load

Note: Photos adapted from Firefighting Tactics Under Wind Driven Conditions.

NIST researchers conducted a series of eight full-scale, multi-compartment fire tests. In each case, a fire was started in the Bedroom using a plastic trash container placed next to the bed (see Figure 3).

Figure 3. Placement of the Trash Container

Note: Photos adapted from Firefighting Tactics Under Wind Driven Conditions.

Experiments

The eight tests provided the opportunity to study the dynamics of wind driven compartment fires and several different approaches to limiting the influence of air intake and controlling the fire.

Experiment 1: This test was performed to establish baseline conditions with no wind

Experiment 2: Evaluation of anti-ventilation using a large wind control device placed over the window

Experiment 3: Evaluation of anti-ventilation using a large wind control device placed over the window (second test with a longer pre-burn before deployment of the wind control device).

Experiment 4: Evaluation of anti-ventilation and water application using a small wind control device and 30 gpm (113.6 lpm) spray nozzle from under the wind control device.

Experiment 5: Evaluation of anti-ventilation and water application using a small wind control device and 30 gpm (113.6 lpm) spray nozzle from under the wind control device (second test with a lower wind speed)

Experiment 6: No wind control device, application of water using a hoseline equipped with a combination nozzle at 90 psi (621 kPa) nozzle pressure, providing a flow rate of 80 gpm (303 lpm).

Experiment 7: No wind control device, application of water using a hoseline equipped with a 15/16″ smooth bore nozzle at 50 psi (345 kPa) nozzle pressure, providing a flow rate of 160 gpm (606 lpm) (test was conducted with the living room corridor door closed).

Experiment 8: No wind control device, application of water using a hoseline equipped with a 15/16″ smooth bore nozzle at 50 psi (345 kPa) nozzle pressure, providing a flow rate of 160 gpm (606 lpm) (second test with the living room corridor door open).

Note: The nozzles for these tests (100 gpm at 100 psi combination nozzle and 15/16″ solid stream nozzle were selected as to be representative of those used by the fire service in the United States (personal correspondence, S. Kerber, February 28, 2009). However, it is important to note that in comparing the results, that the combination nozzle was under pressurized (80 psi, rather than 100 psi) resulting in large droplet size. In addition, the 100 gpm flow rate was 50% of that applied through the solid stream nozzle and is likely considerably lower than the flow capability of combination nozzles typically used with 1-3/4″ (45 mm) hose.

Important Findings

The first experiment was conducted without any external wind or tactical intervention. The baseline data generated during this test was critical to evaluating the outcome of subsequent experiments and demonstrated a number of concepts that are critical to firefighter safety:

Smoke is fuel. A ventilation limited (fuel rich) condition had developed prior to the failure of the window. Oxygen depleted combustion products containing carbon dioxide, carbon monoxide and unburned hydrocarbons, filled the rooms of the structure. Once the window failed, the fresh air provided the oxygen needed to sustain the transition through flashover, which caused a significant increase in heat release rate.

Venting does not always equal cooling. In this experiment, post ventilation temperatures and heat fluxes all increased, due to the ventilation induced flashover.

As discussed in early posts, Fuel & Ventilation and Myth of the Self Vented Fire understanding the relationship between oxygen and heat release rate, the hazards presented by ventilation controlled fires, and the influence of ventilation on fire development is critical to safe and effective fireground operations.

Fire induced flows. Velocities within the structure exceeded 5 m/s (11 mph), just due to the fire growth and the flow path that was set-up between the window opening and the corridor vent.

Avoid the flow path. The directional nature of the fire gas flow was demonstrated with thermal conditions, both temperature and heat flux, which were twice as high in the “flow” portion of the corridor as opposed to the “static” portion of the corridor in Experiment 1 [not wind driven]. Thermal conditions in the flow path were not consistent with firefighter survival.

Previous posts have presented case studies based on incidents in Loudoun County Virginia and Grove City, Pennsylvania in which convective flow was a significant factor rapid fire progress that entrapped and injured firefighters, in one case fatally. Previous NIST research investigating a multiple line-of-duty death that occurred in a townhouse fire at 3146 Cherry Road in Washington, DC in 1999 also emphasized the influence of flow path on fire conditions and tenability.

More to Follow

Subsequent posts will examine the NIST wind driven fire tests in greater detail.

Ed Hartin, MS, EFO, MIFireE, CFO

References

Madrzykowski, D. & Kerber, S. (2009). Fire Fighting Tactics Under Wind Driven Conditions. Retrieved (in four parts) February 28, 2009 from http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part1.pdf; http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part2.pdf;http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part3.pdf;http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part4.pdf.

Madrzykowski, D. & Vettori, R. (2000). Simulation of the Dynamics of the Fire at 3146 Cherry Road NE, Washington D.C., May 30, 1999. Retrieved March 1, 2009 from http://fire.nist.gov/CDPUBS/NISTIR_6510/6510c.pdf

Additional Reading

The following investigative reports deal with firefighter line of duty deaths involving wind driven fire events during structural firefighting.

National Institute for Occupational Safety and Health (NIOSH). (1999). Death in the line of duty, Report F99-01. Retrieved February 28, 2009 from http://www.cdc.gov/niosh/fire/pdfs/face9901.pdf

National Institute for Occupational Safety and Health (NIOSH). (1999). Death in the line of duty, Report F98-26. Retrieved February 28, 2009 from http://www.cdc.gov/niosh/fire/pdfs/face9826.pdf

National Institute for Occupational Safety and Health (NIOSH). (2002). Death in the line of duty, Report F2001-33. Retrieved February 28, 2009 from http://www.cdc.gov/niosh/fire/pdfs/face200133.pdf

National Institute for Occupational Safety and Health (NIOSH). (2007). Death in the line of duty, Report F2005-03. Retrieved February 28, 2009 from http://www.cdc.gov/niosh/fire/pdfs/face200503.pdf

National Institute for Occupational Safety and Health (NIOSH). (2008). Death in the line of duty, Report F2007-12. Retrieved February 28, 2009 from http://www.cdc.gov/niosh/fire/pdfs/face200712.pdf

Prince William County Department of Fire and Rescue (2007). Line of duty investigative report: Technician I Kyle Wilson. Retrieved February 28, 2009 from http://www.pwcgov.org/default.aspx?topic=040061002930004566

Texas State Fire Marshal’s Office. (2001). Firefighter Fatality Investigation, Investigation Number 02-50-10. Retrieved February 28, 2009 from http://www.tdi.state.tx.us/reports/fire/documents/fmloddjahnke.pdf

What is Extreme?

There is some debate about the use of the term extreme fire behavior (some of my colleagues indicate that processes such as flashover is not “extreme” but simply “normal” fire behavior). I contend that flashover would potentially be a normal part of fire development, but is also extreme, at least in the context that we are using the word. As defined in the wildland firefighting community:

“Extreme” implies a level of fire behavior characteristics that ordinarily precludes methods of direct control action. One or more of the following is usually involved: high rate of spread, prolific crowning and/or spotting, presence of fire whirls, strong convection column. Predictability is difficult because such fires often exercise some degree of influence on their environment and behave erratically, sometimes dangerously (National Wildfire Coordinating Group Glossary)

In the structural firefighting environment, occurrence of flashover (particularly while firefighters are operating inside the compartment) fits substantially with the description of extreme used by wildland firefighters.

Classification and Understanding

Ontology may be described as definition of a formal representation of concepts and the relationships between those concepts. An ontology provides a shared vocabulary. Unfortunately we do not have a well developed ontology of fire behavior phenomenon and many types of phenomena have more than one definition. As with the use of the word extreme, there is some debate about the need to classify phenomena as being this or that (e.g., flashover or backdraft). I take the position that it is useful (but difficult as we do not have a common classification scheme or ontology). But, I think that it is still worth the effort.

This is a substantive topic for a later post. This post will examine a type of fire gas ignition phenomena that has been involved in a number of incidents in recent years resulting in near misses, injuries, and fatalities.

Fire Gas Ignitions

In a previous post, I posed the question: Backdraft or Smoke Explosion?. This post used a video clip to open a discussion of the difference between these two phenomena. A smoke (or fire gas) explosion is a type of fire gas ignition, but there are a number of other types of fire gas ignition that present a hazard during firefighting operations.

All fire gas ignitions (FGI) involve combustion of accumulated unburned pyrolysis products and flammable products of incomplete combustion existing in or transported into a flammable state (Grimwood, Hartin, McDonough, & Raffel, 2005). In a smoke explosion, ignition of a confined mass of smoke gases and air that fall within the flammable range results in extremely rapid combustion (deflagration), producing an significant overpressure which can result in structural damage. However, what happens if the mass of gas phase fuel is not pre-mixed within its flammable range and does not burn explosively?

The general term Fire Gas Ignition, encompasses a number of phenomena that are related by the common characteristic that they involve rapid combustion of gas phase fuel consisting of pyrolizate and unburned products of incomplete combustion that are in or are transported into a flammable state. For now, let’s differentiate these phenomena from backdraft on the basis of the concentration of gas phase fuel (backdraft involving a higher concentration than fire gas ignition).

Fire gas ignition can involve explosive combustion (as in a smoke explosion) or rapid combustion that does not produce the same type of overpressure as an explosion. One such phenomenon is a flash fire. In this case, gas phase fuel ignites and burns for short duration, but does not release sufficient energy for the fire to transition to a fully developed stage (as occurs in flashover). While a flash fire may not result in flashover, the energy release is still significant and heat flux (energy transferred) can be sufficient result in damage to personal protective equipment, injury and death. This post uses a case study to examine the flash fire phenomenon.

Residential Fire

This case study is based on a near-miss incident involving extreme fire behavior during a residential fire that occurred on October 9, 2007 at 1119 William Street in Omaha, Nebraska. Special thanks to Captain Shane Hunter (Omaha Fire Department Training Officer) for sharing this post incident analysis and lessons learned.

Unlike many of the incidents used as case studies, no one died or was injured during incident operations. In this near miss incident, the firefighters and officers involved escaped without injury, but the outcome could easily have been quite different.

Weather Conditions

Weather was typical for early fall with a light breeze from the south (blowing towards Side C of the fire building).

Building Information

The fire building was a one and a half story, wood frame dwelling with a basement (see Figure 1). The attic space had been renovated into three separate compartments to provide additional living space.

Figure 1. Exterior View Side A

Figure 2. Floor 2 Layout

Conditions on Arrival

When the first company arrived they observed fire and smoke from the second floor window (see Figure 1) and reported a working fire. The doors and windows on the first floor were closed.

Firefighting Operations

What initial actions were taken? A 200′ hoseline was extended through the door located on Side A and through the living room and kitchen to the stairway to the second floor, which was located at the C/D corner of the structure (Figures 2 and 3).

Figure 5 & 6. Kitchen (view from Floor 1) and Stairwell (view from Floor 2)

What did the fire attack crew observe? The living room and kitchen were clear of smoke and the door to the second floor stairway was closed. When this door was opened and the line was advanced up the stairway to the second floor, the company assigned to fire attack encountered smoke down to floor level on the second floor. Making a left turn at the top of the stairs (see Figure 4) the Captain noted high temperature at the floor level and observed rollover at the ceiling level.

• How did the ventilation profile change when the door to second floor stairway was opened? How might this have changed fire behavior?
• What did the depth of the hot gas layer (from ceiling to floor) indicate about the ventilation profile?
• What did rollover in the center compartment indicate?

The Captain instructed the nozzle operator to apply water to the ceiling. The firefighter on the nozzle applied water in a 30^o fog pattern (continuous application). Simultaneously, a crew working on the exterior vented the second floor window on Side C (see Figures 4 and 6).

How did conditions change? The engine company working on floor 2 heard an audible, whoosh as the hot gas layer ignited producing flames down to floor level. Operation of the hoseline (30^o fog pattern) had no immediate effect. The Captain ordered the crew to retreat into the stairwell and continue water application.

• What extreme fire behavior phenomena occurred?
• What were the initiating events that caused this rapid fire progression?

Figure 4. Floor 2 Side A (Looking Towards Side A)

Figure 5. Floor 2 Side C (Looking Towards Side C)

What action was taken? While the engine company operated from the stairwell, vertical ventilation was completed over the center compartment (see Figures 4 and 5). After the creation of an exhaust opening in the roof, conditions on floor 2 became tenable and the engine crew was able to knock the fire down within several minutes.

• Why did conditions improve quickly after the creation of a vertical exhaust opening?
• What tactical options might have prevented this near miss?

Observations and Analysis

Captain Shane Hunter observed that the initial fire attack crew viewed this incident as an easy job. They thought that an attack from the unburned side would simply push the fire out the window where fire was initially showing on Side A. Why did things turn out so differently than anticipated?

In his analysis of this incident, Captain Hunter points out that there is a considerable difference between a “self-vented” fire and an adequately ventilated fire. As discussed in the April 2008 Officer’s Corner (GFES), horizontally ventilated fires are likely to remain ventilation-controlled. It is important to read the Building, Smoke, Air Track, Heat, and Flame (B-SAHF) indicators to determine the current burning regime (fuel or ventilation-controlled) and anticipate the effect of changes to the ventilation profile.

The fire in the compartment of origin reached flashover resulting in the extension of flames into the center compartment as evidenced by the observation of rollover by the Captain of the engine company performing fire attack. However, the center compartment and the compartment on Side C did not experience flashover (note the condition of contents in the center compartment in Figure 6.). If flashover did not occur in these two compartments, what happened?

In this incident, the fire gases ignited in a flash fire, but combustion did not rapidly transition to a fully developed state in the two compartments adjacent to the compartment of origin.

A flash fire rapidly increases heat release rate, temperature within the compartment and heat flux (as experienced by the fire attack crew in this incident). Like rollover, this phenomenon should not be confused with flashover as fuel in the lower region of the compartment may or may not ignite and sustain combustion. However, fire gas ignition can precede and precipitate flashover (should the fire quickly transition to the fully developed stage).

The concentration of fuel within the hot gas layer varies considerably, with higher concentrations at the ceiling. Concentrations within the flammable range most commonly develop at the interface between the hot gas layer and the cooler air below. Isolated flames (an indicator of a ventilation-controlled fire) are most commonly seen in the lower region of the hot gas layer (as there may be insufficient oxygen concentration in the upper level of the hot gas layer to support flaming combustion). Mixing of the hot gas layer and air due to turbulence increases the likelihood of a significant fire gas ignition.

• What was the ventilation profile and air track when the engine company reached the top of the stairs to begin their attack on the fire?
• How did the tactical ventilation performed from the exterior (removal of the window on floor 2, Side C) influence the ventilation profile and air track?
• What effect do you think that continuous operation of the 30^o fog stream had on conditions on floor 2?
• What combination of factors likely resulting in mixing of air and smoke (fuel) leading to the fire gas ignition that drove the fire attack crew off floor 2 and into the stairwell?

Key Considerations and Lessons Learned

This incident points to a number of key considerations and lessons learned.

• Beware the routine incident! Even what appears to be a simple fire in a small residential structure can present significant challenges and threats to your safety.
• Use the B-SAHF indicators to read the fire and consider both the stage of fire development and burning regime (fuel or ventilation-controlled) in strategic and tactical decision making.
• Flame showing is just that. Do not be lulled into a false sense of security by thinking that the fire is adequately ventilated. Read the air track indicators!
• Continue to read the fire after making entry. Smoke is fuel and hot gases overhead are a threat. Observation of isolated flames indicates a ventilation-controlled fire. Rollover often precedes flashover. Take proactive steps to mitigate the threat of extreme fire behavior.
• Recognize that ventilation-controlled fires will increase in heat release rate if additional air is introduced. Manage the ventilation profile using tactical ventilation and tactical anti-ventilation. Anticipate unplanned ventilation due to fire effects.
• Recognize that both horizontal and vertical ventilation are effective when used appropriately and coordinated with fire control. Consider the influence of inlet and exhaust opening location and size when anticipating the influence of tactical ventilation on fire behavior and conditions within the building.

Again special thanks to Captain Shane Hunter and the Omaha Fire Department for sharing the information about this incident and their work to improve firefighter safety.

Ed Hartin, MS, EFO, MIFireE, CFO

When fire is showing from one or more windows or other opening on arrival, firefighters and fire officers often observe that the fire is �self-vented�. While this is true, this unplanned ventilation often increases heat release rate and does not have the desirable effects resulting from effective tactical ventilation.

Effects of Horizontal Ventilation

Effect of Positive Pressure ventilation on a Room Fire (Kerber & Walton, 2005) describes a series of experiments performed at the National Institute of Standards and Technology (NIST) to determine the effect of horizontal ventilation using a window and door under natural and positive pressure conditions. These experiments involved a compartment with a single window and doorway as illustrated in Figure 1. The room was furnished as a bedroom with a limited fuel load consisting of a bunk bed, bookcase (without books), chair, and desk with computer monitor.

Figure 1. Horizontal Ventilation Test Floor Plan

As illustrated in Figure 2, with natural ventilation the heat release rate (HRR) spiked immediately after the window was vented. As heat release rapidly increased, so too did temperature with peak temperature at the ceiling in excess of 1000^o C (1832^o F).

Figure 2. Heat Release Rate with Natural Horizontal Ventilation

Note: Adapted from Effect of positive pressure ventilation on a room fire, (NISTIR 7213) by S. Kerber & W. Walton

After establishing natural horizontal ventilation by opening the window, a bi-directional air track developed at both the window and door to the compartment as illustrated in Figures 3 and 4. If this compartment was at the end of �a long hallway, what impact would the air track and temperature conditions have on firefighters working their way to the seat of the fire?

Figure 3. Air Track at the Door

Figure 4. Air Track at the Window

Click on the link to view video providing interior and exterior views: NIST Natural Horizontal Ventilation Test . Additional information on natural and positive pressure ventilation tests is also available on the NIST PPV web page.

Horizontal ventilation is often performed to lower temperature and raise the level of the hot gas layer in the fire area. While increased ventilation may accomplish this, failure (or tactical ventilation) of a single window is unlikely to have significant impact on compartment temperature.

Researchers from the University of Texas and the Austin Texas Fire Department (Weinschenk., Ofodike,& Nicks, 2008) performed a computer simulation of the impact of variation in the size of the exhaust opening when performing horizontal ventilation using a window and door. The compartment size was slightly smaller than in the NIST study (Kerber & Walton, 2005) and the fire was considerably smaller (2 MW). In this simulation they examined conditions varying from the window being closed to fully open. As illustrated in Figure 5, even with the window fully open, the temperature in the doorway of the compartment dropped only slightly.

Figure 5. Influence of Opening Size on Doorway Temperature

It is essential to recognize that unplanned ventilation caused by failure of window glazing due to the effects of the fire are unlikely to result in sufficient exhaust opening size to have a significant positive influence on conditions inside the fire compartment and adjacent spaces.

What smoke, flame, and air track indicators would point to ventilation controlled conditions? Take a look at Figures 3 and 4! How might tactical anti-ventilation and/or tactical ventilation be used to positively influence fire conditions and the environment in the compartment?

So What?

Horizontal ventilation is an excellent tool when used correctly. However, not understanding the influence of changes to the ventilation profile when the fire is ventilation controlled, can have disastrous consequences. Ventilation direction (horizontal or vertical), size and location of inlet and exhaust openings, and coordination with fire control are critical to safe and effective fireground operations.

References

For more information, see the following NIST report and journal article.

Kerber, S. & Walton, W. (2005). Effect of positive pressure ventilation on a room fire, (NISTIR 7213). Retrieved January 26, 2009 from http://fire.nist.gov/bfrlpubs/fire05/PDF/f05018.pdf

Weinschenk, C., Ofodike, E., & Nicks, R. (2008) Analysis of fireground standard operating guidelines/procedures for compliance for Austin fire department. Fire Technology, 44(1), 39-64.

Remember the Past

I am involved in an ongoing project to assemble and examine narratives, incident reports, and investigations related to extreme fire behavior events. Unfortunately many of these documents relate to line of duty deaths. As I read through the narratives included in the United States Fire Administration line of duty death database and annual reports on firefighter fatalities, I realized that every week represents the anniversary of the death of one or more firefighters as a result of extreme fire behavior.

While some firefighters have heard about the incidents involving multiple fatalities, others have not and most do not know the stories of firefighters who died alone. In an effort to encourage us to remember the lessons of the past and continue our study of fire behavior, I will occasionally be including brief narratives and links to NIOSH Death in the Line of Duty reports and other documentation in my posts.

January 28, 1994
Firefighter Vencent Acey, 42, Career
Firefighter John Redmond, 41, Career
Philadelphia Fire Department, Pennsylvania

On January 28, Firefighters Vencent Acey and John Redmond, both of the Philadelphia (PA) Fire Department, died when he became trapped and overcome by smoke by a rapidly moving fire in the basement of a church. Several firefighters re-entered the church against orders to rescue the firefighters, and were able to pull one of them from the basement. Eight other firefighters were injured, including several involved in the rescue efforts.

January 28, 1995
Firefighter Victor Melendy, 47, Career
Stoughton Fire Department, Massachusetts

On January 28, Firefighter Victor Melendy of the Stoughton (MA) Fire Department died when he was caught in a flashover while searching for victims on the third floor of a rooming house.

January 27, 2000
Captain Walter Harvey Gass, 74, Volunteer
Sealy Volunteer Fire Department, Texas

Captain Gass and other members of his department were dispatched to a residential structure fire that was caused when lightning struck a house. The first two firefighters on the scene, the Assistant Chief and the Fire Chief, confirmed a working fire with dark smoke and fire visible from the attic and dormers. Captain Gass and his crew were the first fire company to arrive at the scene. Captain Gass and two firefighters entered the structure through the front door to perform an aggressive attack on the fire. Shortly after entering the structure, the two firefighters who were with Captain Gass were attempting to feed more hose into the structure. There was a rapid buildup of heat and the hoseline seemed to drop. The firefighters exited the building and reported this situation to the Chief. Two Rapid Intervention Teams (RIT) were formed and, after four attempts, the second team was successful in recovering Captain Gass. Captain Gass was equipped with full structural protective clothing and a manually activated PASS device. The PASS was found in the “off” position. Captain Gass was located about 18 feet inside the front door of the structure. Captain Gass was removed from the structure approximately 20 minutes after his arrival on the scene. The cause of death was listed as smoke and soot inhalation with greater than 80 percent total thermal injury. Additional information about this incident may be found in NIOSH Fire Fighter Fatality Investigation F2000-09.

Seeking Information

If your department experiences (or has experienced) an extreme fire behavior event and you would be willing to share information about the incident or lessons learned, please contact me by e-mail or telephone.

Warning! Science Ahead

This post attempts to bring some clarity to a few scientific concepts that are often overlooked or oversimplified in fire behavior training for firefighters and fire officers. I have made an effort to make this information accessible, but not to reduce it to the point where it no longer makes sense from a scientific perspective.

Fire Power

In physics, power is the rate at which work is performed or energy expended for a given unit of time. For combustion, power is the energy released per unit of time or heat release rate (HRR). So what? Why is this important to firefighters?

It is relatively easy to describe how big a compartment or building is based on its dimensions (i.e., length, width, height) in meters (or feet). However, describing how big a fire is requires different units of measure. Likely the best way to describe the size� of a fire is on the basis of the rate at which it is releasing energy.

In Heat Release Rate: A Brief Primer, Dr. Vytenis Babrauskas observes that Heat Release Rate (HRR) is the driving force that influences many other dimensions of the fire environment. As HRR increases, temperature and the rate of temperature change both increase, accelerating fire development. In addition, increased HRR results in reduced oxygen concentration and increased production of gaseous and particulate products of incomplete combustion. For firefighters, it is also important that HRR directly relates to flow rate required for fire control.

Measuring Energy and Power

Energy is often defined as the ability to do work or cause change. Thermodynamic work is the transfer of energy from one system to another. This is sometimes, but not always accompanied by an increase in temperature (more on this in a bit).

In the United States, the traditional units of measure for energy were the British thermal unit (Btu). A Btu is the amount of energy required to raise the temperature of one pound of water from 60^o F to 61^o F. Adding additional Btu will continue to raise the temperature of the water until it reaches its boiling point. Changing phase from liquid to gas requires input of a large amount of energy, but there is no change in temperature!

The standard international (SI) unit for energy is the Joule (J). The joule is defined in terms of mechanical energy. However, in our context, it is useful to describe the Joule in terms of transfer of thermal energy. 4186 J will raise the temperature of 1 kilogram (kg) of water from 20^o C to 21^o C. For readers who are more comfortable with Btu, one Btu is equal to 1055 J (slightly more than one kilojoule (kJ)).

Power is the rate at which work is performed or energy is transferred. This necessitates a measure of the amount of energy (i.e., Btu or J) and a unit of time (generally minutes or seconds). Using traditional units, power could be described in terms of Btu/minute or Btu/second. Watts are the SI unit for power, with a Watt being a Joule/second (J/s)

To keep things simple, the remainder of this post will stick to the SI units (Joules, Watts, and ^oC).

Potential Energy of Fuel

Energy that is stored is known as potential energy. Fuel has chemical potential energy that is released as the fuel is oxidized in the combustion process. The energy that is released through complete combustion of a given mass of fuel is known as the heat of combustion. Heat of combustion is dependent on the chemical makeup of the fuel. Heat of combustion is usually expressed in kilojoules/gram (kJ/g) or megajoules/kilogram (MJ/kg).

Generally (hydrocarbon based) synthetic fuels have a higher heat of combustion than cellulose fuels such as wood as illustrated in the following table:

Note: Data in this table is from the Society of Fire Protection Engineering (SFPE) Handbook of Fire Protection Engineering.

When fuel burns, the total energy that can be released is dependent on its heat of combustion and fuel mass (e.g., kg of fuel)

Heat of combustion is important, but as Dr. Babrauskas points out, the rate at which that energy is released is even more important. Heat release rate is influenced by a number of different fuel characteristics such as surface area to mass ratio, orientation (e.g., horizontal, vertical), arrangement, and geometry.

The concepts of heat of combustion and heat release rate help explain changes in the built environment that impact firefighting. Increased use of synthetic materials has increased the chemical potential energy of building materials and contents and higher heat release rates shorten time to flashover.

Oxygen and Combustion

Release of chemical potential energy from fuel depends on availability of adequate oxygen for the combustion reaction to occur. Interestingly, while the heat of combustion of various types of organic (carbon based) fuel varies widely, the amount of oxygen required for release of a given amount of energy remains remarkably consistent.

In 1917, British scientist W.M. Thornton discovered that the amount of oxygen required per unit of energy released from many common hydrocarbons and hydrocarbon derivatives is fairly constant. In the 1970’s, researchers at the National Bureau of Standards independently discovered the same thing and extended this work to include many other types of organic materials and examined both complete and incomplete combustion.

Each kilogram of oxygen used in the combustion of common organic materials results in release of 13.1 MJ of energy. This is referred to as Thornton’s Rule.

However, the concentration of oxygen in the atmosphere is only 21%. Examining the relationship between consumption of atmospheric oxygen and energy release requires adaptation of Thornton’s Rule based on oxygen concentration. Multiplying 13.1 MJ/kg of oxygen by 21% gives a value of 2.751 MJ/kg of air. The Society of Fire Protection Engineering (SFPE) Handbook of Fire Protection Engineering rounds this value to 3.0 MJ/kg of air. While it is easy to understand that air has mass, it is a bit more difficult to visualize a kilo of air! The density of dry air at sea level and at a temperature of 20o C is 1.2 kg/m³ (0.075 lbs./ft³). Air density decreases as temperature or moisture content of the air increases, but this provides a starting point for visualizing the relationship between volume and mass at normal temperature and pressure.

All this is very interesting, but how does it relate to compartment fires and firefighting?

Fuel and Ventilation

In a compartment fire, combustion occurs in an enclosure where the air available for combustion is limited by 1) the volume of the compartment and 2) ventilation.

Consider a 2.4 m x 3.7 m (8′ x 12′) compartment with a ceiling height of 2.4 m (8′). A compartment of this size has a volume of 21.312 m³ (752.63 ft³). Based on a potential heat release of 3 MJ/m³ of air, the volume of the compartment would provide sufficient air for release of 63.936 MJ. A fire burning in this compartment with a steady heat release rate of .5 MW would consume the air in the compartment in just over two minutes (127.8 seconds). However, this is an extreme oversimplification as fires generally begin with a low heat release rate and grow until they become limited by the availability of fuel or oxygen. In this case, the fire would burn for a bit longer and would then cease flaming combustion, but surface combustion may (depending on the type of fuel involved) continue for some time after the oxygen concentration drops below 15%.

It is unlikely that a fire would occur in a compartment that had no openings (or at least potential openings) such as a door and one or more windows. Even if these openings are closed, there will likely be some leakage that will influence the amount of air available to support combustion. If they are open, a substantially greater amount of air will be available to support fire growth. However, as the fire develops and a hot gas layer forms and begins to fill the compartment, exiting smoke reduces the size of the opening serving as an inlet for additional air. As this occurs, the fire becomes ventilation controlled and heat release is limited by the amount of oxygen in the air available to support combustion.

Note: Photos adapted from National Institute of Standards and Technology (NIST) ISO-Room/Living Room Flashover.

Hazard of Ventilation Controlled Fires

Many if not most fires that have progressed beyond the incipient stage when the fire department arrives are ventilation controlled. This means that the heat release rate (the fires power) is limited by the ventilation profile, in particular, the existing openings.

If ventilation is increased, either through tactical action or unplanned ventilation resulting from effects of the fire (e.g., failure of a window) or human action (e.g., exiting civilians leaving a door open), heat release rate will increase.

Ventilation is a complex strategy as it can have both positive and negative effects. Releasing smoke can make the interior environment more tenable by raising the level of the hot gas layer and removing energy and fuel (hot smoke) from the compartment or building. However, increasing the air supply to a ventilation controlled fire will increase the heat release rate, potentially resulting in a ventilation induced flashover.

It is essential that firefighters and fire officers understand the effects of tactical operations on fire behavior and coordinate their efforts to maximize the positive impact while limiting the negative consequences.

Chief Pete Lamb recently wrote a blog post titled Vent Early in which he emphasizes the need for firefighters to understand the application of ventilation strategies and to use them effectively. I suggest that we vent wisely in coordination with fire attack after considering fire behavior and building factors! Understanding compartment fire behavior and practical fire dynamics is critical to safe and effective ventilation operations.

If you found this post interesting or useful (or not), please leave a comment with your feedback.

Ed Hartin, MS, EFO, MIFireE, CFO

Applying NIOSH Recommendations

NIOSH Death in the Line of Duty reports generally contain two types of recommendations, those that focus on specific contributory factors and others that address general good practice. As when examining contributory factors, it is important to read the NIOSH recommendations critically. Do you agree or disagree and why? What would you change and what additional recommendations would you make based on the information presented in the report?

Brief Review of the Incident

NIOSH Report F2008-06 examines a fire in a wood frame duplex that resulted in injury to Lieutenant Scott King and the death of Firefighter Brad Holmes of the Pine Township Engine Company. The fire occurred on February 29, 2008 in Grove City, Pennsylvania.

When the fire department arrived, the unit on Side D was substantially involved and a female occupant was reported trapped in the building. Initial operations focused on fire control and primary search of Exposure B. Rapid fire development trapped Lieutenant King and Firefighter Holmes while they were searching Floor 2 of Exposure B.

The following photographs are part of a series of 37 pictures taken during this incident and provided to NIOSH investigators during their investigation.

Additional detail on this incident is provided in Developing & Using Case Studies: Pennsylvania Duplex Fire Line of Duty Death (LODD) and Pennsylvania Duplex Fire: Firefighting & Firefighter Rescue Operations . In addition, readers should review NIOSH Report F2008-06.

Recommendations

NIOSH Report F2008-06 contains 11 recommendations. Several of these recommendations are well grounded in the contributory factors identified in the report. Others have a more indirect relationship to the factors influencing the injury to Lieutenant King and death of Firefighter Holmes.

Recommendation #1: Fire departments should be prepared to use alternative water supplies during cold temperatures in areas where hydrants are prone to freezing.

In preparation for potential issues, fire departments should develop standard operating procedures (SOPs) for temporary water sources to be dispatched like tankers, water shuttles, or portable drop tanks.

While this recommendation is valid and good practice, it has little to do with loss of water as a contributory and likely causal factor in the injury to Lieutenant King and death of Firefighter Holmes. Had Command been notified immediately of the frozen hydrant and implemented alternate water supply strategies, the outcome would have likely been the same if tank water had been used as it was in this incident to sustain initial operations.

However, it is critical for fire departments to have a plan to respond to respond to water supply problems. In this case, apparatus had substantial tank water which was used to support initial firefighting operations. In addition, there was sufficient hose available on first alarm companies to stretch to other hydrants (such as the one eventually used east of Garden Avenue on Craig Street). Use of a reverse lay to establish water supply allows the apparatus operator to continue the lay to the next hydrant (hose capacity permitting) or another apparatus to continue the lay and establish a relay. Depending on the distance to the next operational water source, this could be considerably more efficient and rapid than waiting for greater alarm resources to establish a tender shuttle.

Recommendation #2: Fire departments should ensure that search and rescue crews advance or are protected with a charged hoseline.

This recommendation is critical. However, the discussion fails to speak to the need for backup lines to protect the means of egress when crews are working above the fire. Recent incidents in Loudoun County, Virginia and Sacramento California, resulted in crews with a hoseline working above the fire without a backup line having their hose burn through, and means of egress cut off, necessitating emergency egress via second floor windows.

Recommendation #3: Fire departments should ensure fire fighters are trained in the tactics of a defensive search.

While training in search under marginal circumstances is important, this recommendation fails to speak to the need to understand fire behavior and applied fire dynamics as a foundation for maintaining situational awareness on the fireground. This applies to command personnel, company officers, and individual firefighters. While there are a number of points in the sequence of events that lead to Lieutenant King’s injury and Firefighter Holmes’s death, all are dependent on this. Failure to recognize the potential for extension and rapid fire progress, the influence of creating ventilation openings on Floor 2, and recognition of developing fire conditions were likely the most significant causal factor in this incident. Had this not been the case, the firefighters and officers involved would have had the opportunity to adjust their tactical operations or exit the building prior to the occurrence of the extreme fire behavior that trapped the search team.

NIOSH Report F2008-06 quotes Deputy Chief Vincent Dunn regarding flashover indicators:

There are two warning signs that may precede flashover: heat mixed with smoke and rollover. When heat mixes with smoke, it forces a fire fighter to crouch down on his hands and knees… As mentioned above, rollover presages flashover.

This statement is scientifically incorrect. Heat is simply energy in transit due to temperature difference. It is not a substance and cannot mix with anything else. Increasing temperature is an indicator of potential for flashover, but perception of a rapid increase in temperature is not certain to give adequate warning to take corrective action or escape from the hazardous situation. In addition, rollover does not always precede flashover (it is an important indicator, but only one of many).

The report also quotes Chief Dunn regarding defensive search tactics.

Three defensive search tactics are as follows:

1. At a door to a burning room that may flashover, fire fighters should check behind the door to the room and sweep the floor near the doorway. Fire fighters should not enter the room until a hose line is in position.
2. When there is a danger of flashover, fire fighters should not go beyond the “point of no return.” The point of no return is the maximum distance that a fully equipped fire fighter can crawl inside a superheated, smoke-filled room and still escape alive if a flashover occurs. The point of no return is approximately five feet inside a doorway or window.
3. When searching from a ladder tip placed at a window, look for signs of rollover if one of the panes has been broken. If rollover is present, do not go through the window. Instead, crouch below the heat and sweep the interior area below the windowsill with a tool. If a victim has collapsed there, you may be able to crouch below the heat enough to pull him to safety.

While these tactics have validity, making for search without without protection of a hoseline even to Chief Dunn’s “point of no return”� presents a significant risk. Further, I am uncertain that there is any scientific evidence supporting the concept of the point of no return as described by Chief Dunn. There are numerous examples of situations where firefighters thought they had time to complete a search, but were trapped by extremely rapid fire development. The risk of searching under marginal conditions requires firefighters to effectively read the fire and mitigate hazards in the fire environment through effective use of gas cooling and control of the ventilation profile (either tactical ventilation or anti-ventilation as appropriate) and establishing fire control in addition to primary search.

Recommendation #4: Fire departments should ensure that fire fighters conducting an interior search have a thermal imaging camera.

The thermal imaging camera is a tremendous technological innovation which can significantly speed search operations and provide visual indication of differences in thermal conditions. However, implementation of this recommendation would not necessarily have impacted on the outcome of this incident.

Recommendation #5: Fire departments should ensure ventilation is coordinated with interior fireground operations.

In the discussion of this recommendation, the NIOSH Report F2008-6 states “By eliminating smoke, heat, and gases from the fire it will help minimize flashover conditions”�

This statement is not always true. The influence of ventilation on fire development is dependent on burning regime (fuel or ventilation controlled) and the location of the inlet and exhaust openings. Heat release rate from a ventilation controlled fire will increase as ventilation is increased, potentially taking the fire to flashover (rather than the reverse as indicated by the statement in this NIOSH report). In addition, creation of an air track that channels the spread of hot gases and flames to additional fuel packages can result in fire extension and subsequent flashover. Both of these factors were likely to have been significant in this incident. Coordination of ventilation and search or ventilation and fire attack (as frequently stated in NIOSH reports related to incidents involving extreme fire behavior) requires knowledge of fire dynamics and the influence of ventilation in fire behavior.

Recommendation #6: Fire departments should ensure that Mayday protocols are developed and followed.

This recommendation is important, but fails to address other individual level survival skills that must be integrated with these procedures. For example, in this incident, the Lieutenant and Firefighter might have been able to take refuge in one of the bedrooms, closing the door to provide a barrier to hot gases and flames. A ladder was initially placed to a window in the bedroom on Side B (in close proximity to the location where Firefighter Holmes was found). Ladders were subsequently placed to the bedroom windows on Side A. While it may have been difficult to accomplish this under conditions of extreme thermal insult, if developing conditions had been recognized soon enough (see my earlier observation on situational awareness), this may have bought critical seconds and allowed the trapped search team to escape or be rescued.

Recommendation #7: Fire departments should ensure that the Incident Commander receives pertinent information during the size-up (i.e., type of structure, number of occupants in the structure, etc.) from occupants on scene and that information is relayed to crews upon arrival.

Had the Incident Commander received more specific information from the occupants or law enforcement, this may have shifted focus in search operations as survivability in the original fire unit was doubtful. Despite this, the civilian casualty was later located outside the fire unit, behind the door in the front foyer that served both dwelling units.

Recommendation #8: Fire departments should ensure that fire fighters communicate interior conditions and progress reports to the Incident Commander.

This is a key element in maintaining situational awareness (on the part of the Incident Commander). However, it is equally important for Command to communicate with interior crews regarding conditions observed from the exterior or situations (such as water supply limitations) that will impact interior operations.

Recommendation #9: Fire departments should develop, implement, and enforce written standard operating procedures (SOPs) for fireground operations.

This recommendation focuses on general good practice, but is not tied to specific contributing factors related to the injuries and fatality that resulted in this incident. This type of recommendation should likely be included, but placed in a separate section so as not to dilute the focus on lessons learned.

Recommendation #10: Fire departments and municipalities should ensure that local citizens are provided with information on fire prevention and the need to report emergency situations as soon as possible to the proper authorities.

Recommendation #11: Building owners and occupants should install smoke detectors and ensure that they are operating properly.

If implemented prior to this incident, Recommendations #10 and #11 would likely have had a positive impact on its outcome, particularly with regards to the civilian casualty and the severity of conditions encountered by the firefighters.

However, these two recommendations do not go far enough. Citizens must also recognize the need for rapid egress and the value of closing doors to confine the fire and limit inlet of air required for continued fire development and increasing heat release rate.

Detailed Case Study

CFBT-US has developed a detailed case study based on this incident and the data contained in NIOSH Report F2008-06. Download the Grove City, Pennsylvania Residential (Duplex) Fire Case Study in PDF format.

Now What?

Over the last two weeks we have spent considerable time with a NIOSH Report F2008-06. NIOSH has completed 335 investigations during the first 8 years that this program has been in existence. 49 more investigations are pending. The information contained in these reports provides a vast reservoir of data that can be used to deepen understanding of your craft and improve decision-making and risk management skills.

Make a commitment to developing your expertise as a firefighter or fire officer in the new year and for the rest of your life. Look for the this logo (more information to follow)!

Have a safe and happy new year!

Ed Hartin, MS, EFO, MIFIreE, CFO

I would like to extend my thanks to Steve Berardinelli and Tim Merinar of the NIOSH Firefighter Fatality Investigation and Prevention Program for their assistance in developing the Case Study based on NIOSH Report F2008-06. Just prior to my first post regarding this incident, I forwarded a request for additional information to the NIOSH staff and received a quick response from Tim that he would forward my request to the investigators. This morning I had an excellent conversation with Steve and obtained additional information that was extremely helpful in refining the case.

I will be revising Developing & Using Case Studies: Pennsylvania Duplex Fire Line of Duty Death (LODD) and Pennsylvania Duplex Fire: Firefighting & Firefighter Rescue Operations based on additional information provided by NIOSH. Changes include addition of information related to the ventilation profile, initial fire conditions, and occupant actions.

Analysis and Critique

It is important to note that the observations in this post regarding the contributory factors identified in NIOSH Report F2008-06 are made as a critical friend. Most firefighters and fire officers who read this (or any) NIOSH report will agree with some of the recommendations, may disagree with others, and undoubtedly would make additional recommendations based on their individual assessment of the incident. Analysis of contributing factors and recommendations (rather than simply accepting them) is an important element in the learning process. Dig a bit deeper and build an understanding of why events may have unfolded the way that they did. Identify the critical points at which the outcome could have been changed (there are likely more than one). Think about how these recommendations might apply to you and your department.

As discussed in my earlier post; Criticism Versus Critical Thinking, the intent of this analysis and critique is to share what I have learned from this case, with all due respect to those involved. The firefighters and fire officers involved in this incident were faced with a difficult situation to begin with, having an occupant reported trapped in the building. This was compounded by challenging water supply problems due to multiple frozen hydrants. It is far easier to examine incident information in a comfortable environment with no time pressure than to deal with these issues in the cold, early morning hours.

My original intent was to examine both the contributory factors and recommendations in NIOSH Report F2008-06. However, due to length, this critique will be divided into two separate posts.

A Brief Review of the Incident

On February 29, 2008 The Grove City Fire Department, Pine Township Engine Company, and East End Fire Department responded to a fire in a two-story, wood frame duplex in Grove City, Pennsylvania. Initial dispatch information and the initial size-up indicated that a female occupant was trapped in the building. When the Chief and first engine company arrived, the unit on Side D was substantially involved with smoke in the unit on Side B. Several hoselines were placed into operation for fire control, but fire conditions precluded an offensive attack in the involved unit. Pine Township Engine 85 was assigned to search and rescue of the trapped occupant. Firefighter Brad Holmes and Lieutenant Scott King were tasked with primary search of Exposure Delta. Firefighting operations were hampered by two frozen hydrants, necessitating support of initial operations using only apparatus tank water while an operable hydrant was located. During their search, water supply was interrupted and rapidly deteriorating conditions trapped the search crew. After being rescued by the Rapid Intervention Team, both members were transported to Pittsburgh’s Mercy Hospital Burn Unit. Firefighter Brad Holmes had burns over 75% of his body, and died from his injuries on March 5, 2008. Lieutenant King suffered less serious injuries and was treated and released. A 44 year old female occupant of the dwelling also died.

Figure 1. 132 Garden Avenue-Side Alpha

Note: Fire Department Photo – NIOSH Death in the Line of Duty Report F2008-06. This photo likely illustrates conditions after 0635 (approximately 19 minutes after arrival of the first fire unit, Chief 95).

Additional detail is provided in Developing & Using Case Studies: Pennsylvania Duplex Fire Line of Duty Death (LODD) and Pennsylvania Duplex Fire: Firefighting & Firefighter Rescue Operations. In addition, readers should review NIOSH Report F2008-06.

Contributory Factors

NIOSH Report F2008-06 identifies seven contributory factors in the injury of Lieutenant King and death of Firefighter Holmes. While each of these factors may have had some influence on the outcome of this incident, this analysis provides insufficient clarity and misses several key factors.

• Inadequate water supply. Two hydrants in the vicinity of the burning structure were frozen from the cold weather.
• The victim and injured Lieutenant did not have the protection of a charged hoseline during their search for the trapped occupant.
• Inadequate training in defensive search tactics.
• Non-use of a thermal imaging camera which may have allowed the search and rescue crew to advance more quickly through the structure.
• Ventilation was not coordinated with the interior search.
• Size-up information about the structure was not relayed to the interior search crew. The interior crew was searching in the wrong duplex for the trapped occupant and did not realize they were in a duplex.
• The incident commander was unaware of the search crew’s location in the building. He did not receive any interior reports and was concentrating on resolving water supply issues.

Water Supply: The lack of a continuous water supply likely influenced the loss of the structure and loss of water supply to handlines was in all probability a causal factor in the injury of Lieutenant King and death of Firefighter Holmes. However, the volume of tank water available on apparatus that arrived prior to the search team becoming trapped on Floor 2 (5000 gallons) was likely adequate to support search of the uninvolved areas of the building and confine the fire to the unit of origin for the time required to search uninvolved areas of the building. Anticipation that a continuous water supply would be established may have influenced the tactics and water application used by initial arriving companies.

Protection of the Search Team: Failure to protect the search team with a hoseline was a significant factor in this incident. However, the outcome would likely have been the same if the search team had a hoseline as fire extended from below to cut off their means of egress. A backup line should also have been in place to protect the search team’s egress while they were working above the fire. There was an additional hoseline initially deployed to the doorway on Side A, however, the position and operation of this line while the search team was on Floor 2 was not specified in the report. Without additional tactical changes, the loss of water supply would have precluded effective hoseline support of search operations.

Training in Defensive Search Tactics: Identifying a lack of training in “defensive search tactics” is too narrowly focused. The issue here is significantly broader than stated in the report and should be restated as lack of situational awareness. This causal factor fails to identify the lack of situational awareness on the part of the search crew, the incident commander, and others on the fireground to developing and potential fire conditions and water supply limitations. This lack of situational awareness is likely due to inadequate training in fire behavior and applied fire dynamics (rather than simply inadequate training in defensive search tactics).

Use of a TIC: Undoubtedly effective use of a TIC can speed search operations. However the NIOSH report indicated that visibility was not excessively compromised during the initial stages of search on both floors 1 and 2. Reducing the time required to complete the search could have been influenced by use of a TIC, by assigning a separate crew to perform fire control on Floor 1 of Exposure B and allowing Firefighter Holmes and Lieutenant King to focus on primary search or by both of these actions. While technology may useful in improving firefighter safety, it is important to not simply look for a technological solution to a problem which can be substantively related to human factors such as situational awareness, communications, and decision-making.

Tactical Ventilation: The location, sequence, and lack of coordination in ventilation was likely a causal factor (along with failure to protect the means of egress with a hoseline and loss of water supply) in the injury to Lieutenant King and death of Firefighter Holmes. Creation of exhaust openings above the fire created a clear path of travel for hot gases and flames from Floor 1 to Floor 2 via the interior stairs and increased air supply to a fire which was likely ventilation controlled (resulting in an increase in heat release rate (HRR) sufficient to result in flashover. This contributory factor also points to the need for training on the influence of tactical operations (particularly ventilation) on fire behavior.

Communication of Size-Up Information: Size-up information related to the building and possible victim location could have been a significant factor in focusing the location of the search. However, the civilian occupant was not in either unit, but was located (after fire control) behind the door in the foyer. If it was known that the trapped occupant was from the fire unit, it may have appeared that there was no savable life (due to the extent of fire involvement). But this does not preclude the assumption that she may have been confused and gone into the other unit.

Note: There is some difference of opinion between the fire investigator and operational personnel as to the likely location of the victim prior to structural collapse. It is possible that the victim died on Floor 2 of the fire unit and fell to the position where she was found due to structural collapse.

Accountability and Situation Status: Accountability and communication of situation status is critical to the safety of everyone operating on the fireground. Clear communication in advance of the loss of water supply could have influenced the outcome of this incident. When operating off tank water, it is essential to follow a similar philosophy as the Rule of Air Management and retain sufficient water to exit from the hazardous environment. However, it does not appear that the lack of accountability regarding the search team significantly delayed the rescue effort.

My next post will examine the recommendations made in NIOSH Report F-2008-06 and will provide a link to a detailed, written case study based on this incident in PDF format.

Happy Holidays,
Ed Hartin, MS, EFO, MIFireE, CFO

This post continues examination of NIOSH Death in the Line of Duty Report F2008-06. My previous post, Developing & Using Case Studies: Pennsylvania Duplex Fire Line of Duty Death (LODD) emphasized the importance of case studies to individual and organizational learning and presented initial information about the incident which resulted in injury to Lieutenant Scott King and the death of Firefighter Brad Holmes of Pine Township Engine Company.

Figure 1. 132 Garden Avenue-Side Alpha

Note: Fire Department Photo – NIOSH Death in the Line of Duty Report F2008-06. This photo likely illustrates conditions after 0635 (approximately 19 minutes after arrival of the first fire unit, Chief 95).

Firefighting Operations

Command assigned Engine 95 (officer and five firefighters) to fire suppression. They deployed a 1-3/4″� (45 mm) line to the door on Side A, but were unable to make entry due to the volume of fire in the involved unit. Engine 95 also deployed a 2-1/2″� (64 mm) handline to the A/D corner. Both lines were immediately placed into operation. NIOSH Report F2008-06 indicated that the 1-3/4″� line stretched to the door on Side A was “unable to make entry due to heavy fire conditions”�. However, exact placement and operation of the 2-1/2” handline was not specified. This line may have been used to protect Exposure D (a wood frame dwelling approximately 20′ from the fire unit), for defensive fire attack through first floor windows, or both.

Figure 2. Fire Unit and Exposure Bravo Floor 1

Note: This floor plan is based on data provided in NIOSH Report F2008-06 and is not drawn to scale. Windows shown as open are based on the narrative or photographic evidence. Door position is as shown based on information provided by NIOSH Investigator Steve Berardinelli (this differs from the NIOSH report which includes the fire investigators rough sketch showing all doors open). Windows shown as intact are not visible in the available photographs, but may be open due to fire effects or firefighting operations (particularly those in the fire unit).

Second due, Engine 95-2 performed a forward lay from a nearby hydrant and supplied Engine 95 with tank water while waiting for the supply line to be charged.

Engine 85 (chief, lieutenant, and three firefighters) was assigned to primary search and rescue of the trapped occupant. Tasked to conduct primary search in Exposure B, Firefighter Holmes and Lieutenant King were performed a 360^o reconnaissance prior to making entry. While this was being done other members of the company placed a ladder to a window on Floor 2 Side B (see Figure 3). The NIOSH Report does not specify if the search team was aware of ladder placement.

The Officer of Engine 95 vented the window on Floor 1 Side A of Exposure Bravo and observed that the ceiling light was on (indicating that there was limited optical density of the smoke on Floor 1 of the exposure). Firefighter Holmes and Lieutenant King entered through this window (see Figure 2) to conduct primary search of the exposure and observed that the temperature was low and there was limited smoke on Floor 1. Engine 95 passed the search team a 1-3/4″� (45 mm) handline through the window and the search team knocked down visible fire extension and completed their search of the first floor. At this point, Firefighter Holmes and Lieutenant King left the hoseline on Floor 1, went up the stairs to Floor 2 and began a left hand search.

Figure 3. Fire Unit and Exposure Bravo Floor 2

Note: See the prior comments regarding windows and door position.

The Officer of Engine 95 noticed that the search crew had finished their search on the first floor and were advancing to the second floor. He placed a ladder and broke the window on Floor 2, Side A (See Figure 3). He stated that there was not much heat on the second floor because the plastic insulation on the window was not melted, but he did notice heavy black smoke beginning to bank down. The NIOSH Report did not specify the depth of the hot gas layer (down from the ceiling) or the air track at the window that was vented or Floor 1 openings (windows and door).

The hydrant that Engine 95-2 laid in from was frozen as was the hydrant several houses beyond the fire buildingFirst alarm companies used tank water to support initial firefighting operations. The crew from Engine 95-2 began to hand stretch a 3″� line to a working hydrant on a nearby cross street.

After Firefighter Holmes and Lieutenant King partially completed their search of Floor 2, Lieutenant King’s air supply was at one half and Firefighter Holmes was unsure of his air status, so the Lieutenant decided to exit. At approximately the same time, Engine 95 ran out of water and the Command ordered companies to abandon the building with Engine 85 sounding its air horn as an audible signal to do so. The Accountability Officer called for a Personnel Accountability Report (PAR), but received no response from Lieutenant King or Firefighter Holmes.

Almost immediately after Engine 95 ran out of water, conditions changed rapidly decreasing visibility and increasing temperature on Floor 2 of Exposure B and fire involvement of Floors 1 and 2 of both units. With deteriorating conditions on the second floor, Lieutenant King became disoriented and separated from Firefighter Holmes. He radioed for help at 0638 hours. “Help! Help! Help! I’m trapped on the second floor!” In a second radio transmission, Lieutenant King indicated he was at a window on Side D.

Firefighter Rescue Operations

After hearing radio traffic that the search crew could not find their way out and they were by a window the Engine 95 officer accessed a window on Side B Floor 2 (using a ladder previously placed by Engine 85-2). He broke out the window to increase ventilation and attempt contact with the search team.

A crew from Engine 77 was tasked as a second search team and preparing for entry when the IC ordered companies to withdraw. However, when they heard the Lieutenant’s call for help, they immediately went to Side D, not seeing the Lieutenant at the window, they continued to Side B. The officer from Engine 77 climbed the ladder they had placed earlier to attempt contact with the initial search team. There was heavy black smoke coming from this window, but no fire. He straddled the window sill attempting to hear any movement, a PASS device, or voices. He banged on the window sill as an audible signal to the search team, but received no response. He also attempted to locate the search team using a TIC, however, it malfunctioned.

Flames now pushing out the first floor windows of both the unit originally involved in fire as well as Exposure B. Lieutenant King managed to find his way to the staircase, stumbled down the stairs and out the door on Side A. His protective clothing was severely damaged and smoldering. He collapsed in the front yard and told the other firefighters that the victim was trapped on the second floor. The RIT (R87) made entry supported by a hoseline operated from the entry point by Engine 85-2. Firefighter Holmes was located approximately 10′ (3 m) from the top of the stairs (as illustrated in Figure 3). He was semi-conscious and on his hands and knees. The RIT removed Firefighter Holmes via the stairway to Side A. Lieutenant King and Firefighter Holmes were transported to a local hospital where they were stabilized prior to transport to the Mercy Hospital’s Burn Unit in Pittsburgh.

Questions

The following questions provide a basis for examining the second segment of this case study. While limited information is provided in the case, this is similar to an actual incident in that you seldom have all of the information you want.

1. What was the stage of fire development and burning regime in the fire unit when the search team entered the exposure?
2. What Building, Smoke, Air Track, Heat, and Flame (B-SAHF) indictors can be observed in Figure 1?
3. What was the stage of fire development and burning regime in Exposure B when the search team entered?
4. What type of extreme fire behavior event occurred in the exposure, trapping Firefighter Holmes and Lieutenant King? What leads you to this conclusion?
5. What were the likely causal and contributing factors that resulted in occurrence of the extreme fire behavior that entrapped the Firefighter Holmes and Lieutenant King?
6. What self-protection actions might the search team have taken once conditions on Floor 2 of Exposure B began to become untenable?
7. What action could have been taken to reduce the potential for extreme fire behavior and maintain tenable conditions in Exposure B during primary search operations?
8. What was the tactical rate of flow for full involvement of a single unit in this building? (The tactical rate of flow is the flow required for fire control and does not include the flow rate for backup lines.)
9. What factors may have influenced the limited effectiveness of the 1-3/4” and 2-1/2” attack lines deployed by Engine 95?
10. What tactical options might have improved the effectiveness of fire control operations given the available water supply?

My next post will examine the contributing factors and recommendations made in NIOSH Death in the Line of Duty Report F2008-06 and will include a link to a more detailed written case study of this incident in PDF format.

Ed Hartin, MS, EFO, MIFireE, CFO

This post is a continuation of my feedback to the National Institute for Occupational Safety and Health that will be presented at the public stakeholder meeting conducted in Chicago, IL on 19 November 2008. My recommendations are presented in the form of an analysis of NIOSH Report F2007-29. This incident resulted in the death of Captain Kevin Williams and Firefighter Austin Cheek of the Noonday Volunteer Fire Department.

This post continues with discussion the NIOSH reports examination of the influence of ventilation in this incident and provides specific recommendations for improvement of the NIOSH Firefighter Fatality Investigation and Prevention Program.

Tactical Ventilation

The NIOSH report makes a general recommendation that “fire departments should ensure that properventilation is done to improve interior conditions and is coordinated with interior attack”� [emphasis added]. However, the report is misleading and fails to address key issues related to tactical ventilation, its effective application, and its tremendous influence fire behavior.

NIOSH Report F2007-29 indicated that positive pressure ventilation was initiated prior to the second entry by the initial attack crew (a significant difference from the information provided in the Texas State Fire Marshal’s report). However, no mention is made of any action (or lack thereof) to create an adequate exhaust opening for effective horizontal positive pressure ventilation. While advising that ventilation needs to be proper, it would be helpful to provide more specific guidance. Lack of an adequate exhaust opening prior to pressurizing the building has been a major factor in a number of incidents in which application of positive pressure resulted in extreme fire behavior such as ventilation induced flashover or backdraft. Positive Pressure Attack for Ventilation and Firefighting (Garcia, Kauffmann, & Schelble, 2006), Fire Ventilation (Svensson, 2000), and Essentials of Firefighting (IFSTA, 2008) all emphasize the importance of creating an adequate exhaust opening prior to application of positive pressure.

The NIOSH report pointed out that smoke pushed out the inlet and overrode the effects of the blower, but attributed this to the presence of an attic floor that interfered with vertical ventilation rather than the lack of an adequate exhaust opening for the initial horizontal ventilation.

The PPV fan and vertical ventilation had little effect due to an attic floor being installed. At 0231 Chief #2 had horizontally vented the window on the D side near the A/D corner.

In this incident, ventilation was being performed while the interior attack crew was already inside working. When the ventilation was completed, minimal smoke was pushed out of the vented hole but dark smoke pushed out of the front door, in spite of the fact that a PPV fan was set up at the front door. Note: The dark smoke pushing out the door indicated that the conditions were worsening and the vertical ventilation was not impacting the fire.

In addition, the report fails to note that the opening made on Side D near the AD Corner placed the attack team between the fire and an exhaust opening. As with lack of an adequate exhaust opening, this has been demonstrated to have the potential for disastrous consequences (see NIOSH Death in the Line of Duty F2004-02).

Floor Plan Illustrating the Position of Captain Williams and Firefighter Cheek

Texas State Fire Marshal’s Office Firefighter Fatality Investigation Report FY 07-02

Extreme Fire Behavior

Command ordered companies to abandon the building at 0234 hours using three air horn blasts as an audible signal. The NIOSH report indicated that heavy fire “continued to roll out the front door”� but it is unclear how soon this occurred after smoke conditions at the doorway changed.

NIOSH Report F2007-29 does not clearly identify that extreme fire behavior was a causal or even contributory factor in the deaths of Captain Williams and Firefighter Cheek. It simply states that they died as a result of smoke inhalation and thermal burns.

NIOSH Recommendations

NIOSH made six recommendations based on analysis of the incident in which Captain Williams and Firefighter Cheek lost their lives. Several of these recommendations focused on factors that may have contributed to these two LODD. These included radio communications equipment and procedures, accountability, rapid intervention, and the importance of mutual aid training. Two recommendations were more directly related to causal factors: The importance of ongoing risk assessment and use of proper and coordinated ventilation. However, these broad recommendations miss the mark in providing useful guidance in minimizing the risk of similar occurrences.

Ensure that the IC conducts a risk-versus-gain analysis prior to committing to interior operations and continue the assessment throughout the operation.

This statement is necessary but not sufficient. Size-up and risk assessment is not only the responsibility of the incident commander. All personnel on the fireground must engage in this process within the scope of their role and assignment. Understanding practical fire dynamics is critical to firefighters’ and fire officers’ ability to recognize what is happening and predict likely fire behavior and the influence of tactical operations. To effectively address this issue, NIOSH death in the line of duty reports must be explicit and detailed with regards to key fire behavior indicators observed, subsequent fire behavior phenomena, and the influence of the action or inaction of responders on fire development.

Fire departments should ensure that proper ventilation is coordinated with interior attack.

NIOSH Report 2007-29 focused on the ineffectiveness of the vertical ventilation, but failed to recognize the impact of the sequence of action (i.e. pressurization of the building and creation of exhaust openings), inadequacy of initial exhaust openings, and eventual location of exhaust openings in relation to the operating position of Captain Williams and Firefighter Cheek.

As with situational awareness, effective tactical operations are grounded in training, education, and experience. The incident commander and crews tasked with carrying out tactical ventilation must understand how these tactics influence the fire environment and fire behavior. As with size-up and risk assessment, this is dependent on an understanding of practical fire dynamics.

Other than indicating that ventilation must be coordinated with interior attack, the NIOSH report did not speak to fire control operations conducted during this incident. From the building floor plan and information presented in both the reports by NIOSH and the Texas State Fire Marshal, it appears that the fire was shielded and direct attack was not possible from the position of the first attack team nor the position reached by Captain Williams and Firefighter Cheek. The Fire Marshal’s report indicated that the initial attack team “penciled”� the ceiling to control flames overhead and experienced disruption of the hot gas layer and an increase in temperature at floor level.

Just as ventilation must be appropriate and coordinated with interior fire attack, fire control must also be appropriate and coordinated with tactical ventilation. Cooling the hot gas layer is an appropriate tactic to create a buffer zone and increase the safety of the attack team as they access a shielded fire. However, penciling (use of an intermittent application of a straight stream) the ceiling is an ineffective method of cooling the hot gas layer and results in excessive steam production. In addition, cooling the hot gas layer is not an extinguishment technique; it must be integrated with other fire control methods such as a direct attack on the seat of the fire.

NIOSH death in the line of duty reports must explicitly address the effect of tactical operations, particularly where effectiveness or ineffectiveness was a contributing or causal factor in the LODD.

The Way Forward

While this assessment has been quite critical of NIOSH’s investigation of traumatic fatalities involving extreme fire behavior, it is important to emphasize that with all its faults, the Firefighter Fatality Investigation and Prevention program is a tremendous asset to the fire service.

The following recommendations are made to further strengthen and improve the quality of this program and the utility of recommendations made to reduce the risk of firefighter line of duty deaths as a result of extreme fire behavior during structural firefighting operations:

• Emphasize the criticality of understanding fire behavior, causal factors in extreme fire behavior, and the influence of tactical operations such as fire control and ventilation.
• Increase attention to building, smoke, air track, heat, and flame indicators when investigating incidents which may have involved extreme fire behavior as a causal or contributing factor in LODD.
• Examine training in greater detail, with specific emphasis on fire behavior, situational assessment, realistic live fire training, and crew resource management.
• Provide fire behavior training to all NIOSH investigators to improve their understanding of fire development, extreme fire behavior phenomena, and the impact of tactical operations.
• Include a fire behavior specialist on the investigation team when investigating incidents that may have involved extreme fire behavior as a causal or contributing factor.
• Initiate investigations quickly to avoid degradation of the quality of information obtained from the individuals involved in the incident and other witnesses.

Ed Hartin, MS, EFO, MIFireE, CFO

References

National Institute for Occupational Safety and Health (NIOSH). (2008). Death in the line-of-duty… Report 2007-29. Retrieved November 14, 2008 from NIOSH http://www.cdc.gov/NIOSH/FIRE/reports/face200729.html.

Texas State Fire Marshal’s Office (2008). Firefighter fatality investigation FY 07-02. Retrieved November 14, 2008 from http://www.tdi.state.tx.us/reports/fire/documents/fmloddnoonday.pdf

Svensson, S. (2000). Fire ventilation. Karlstad, Sweden: Swedish Rescue Services Agency

Garcia, K., Kauffmann, R., & Schelble, R. (2006). Positive pressure attack for ventilation & firefighting. Tulsa, OK: Pen Well

International Fire Service Training Association. (2008) Essentials of Firefighting (5th ed). Stillwater, OK: Fire Protection Publications.