Posts Tagged ‘fire behavior’

My last post introduced a National Institute for Standards and Technology research project examining firefighting tactics for wind driven structure fires (particularly those occurring in high-rise buildings). The report on this research Firefighting Tactics Under Wind Driven Conditions contains a tremendous amount of information on this series of experiments including heat release rate, heat flux, pressure, velocity, and gas concentrations during each of the tests along with time sequenced still images (video and infrared video capture).

This post will examine the initial test used to establish baseline conditions for evaluation of wind driven fire conditions and tactics. Readers are encouraged to download a copy of the report and dig a bit deeper!

Test Conditions

In Wind Driven Fires, I provided an overview of the multi-compartment test structure and fuel load used for this series of experiments. To quickly review, 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 (between the Bedroom and Living Room) and exterior corridor. Fuel load consisted of typical residential furnishings in the bedroom and living room along with carpet and carpet pad throughout the structure. The target room (used to assess tenability in a potential place of refuge for occupants or firefighters) did not contain any furnishings. Different types of doors (metal, hollow core wood, etc.) were used in the tests to evaluate performance under realistic fire conditions.

Two ventilation openings were provided, a ceiling vent in the Northwest Corridor (providing a flow path from the involved compartment(s) into the corridor) and a window (fitted with glass) in the compartment of origin. During the fire tests, the window failed due to differential heating (of the inner and outer surface of the glass) and was subsequently removed by researchers to provide the full window opening for ventilation.

Figure 1. Isometric Illustration of the Test Structure

Note: The location of fuel packages in the bedroom and living room is shown on the Floor Plan provided in Wind Driven Fires post.

The structure was constructed under a large oxygen consumption calorimetry hood which allowed measurement of heat release rate (once products of combustion began to exit the ceiling vent). In addition, thermocouples, heat flux gages, pressure transducers, and bidirectional probes were used to measure temperature, heat flux, pressure, and gas flow within and out of the structure. Gas sampling probes were located at upper and lower levels, (0.61 m (2′) and 1.83 m (6′) below the ceiling respectively) in the bedroom and living room. Researchers measured oxygen, carbon dioxide, carbon monoxide, and total hydrocarbon concentration during each test.

Experiment 1 Baseline Test

This experiment was different than the others in the series as no external wind was applied to the structure. The fire was ignited in the bedroom and allowed to develop from incipient to fully developed stage in the bedroom.

After 60 seconds the fire had extended from the trash can (first fuel package ignited) to the bed and chair. At this point a visible smoke layer had developed in the bedroom.

120 seconds after ignition, the smoke layer had reached a thickness of 1.2 m (4′) in the bedroom, hallway, and living room. At this point, smoke had just started to enter the corridor. Conditions in the target room were tenable with little smoke infiltration.

At 180 seconds after ignition, the smoke layer was 1.5 m (5′) deep and had extended from the living room into the corridor. Flames from the bed and chair had reached the ceiling. Hot smoke and clear air was well stratified with a distinct boundary between upper and lower layers. Smoke had begun to infiltrate at the top of the door to the target room.

240 seconds after ignition the window started to fail due to flame impingement and the smoke layer extended from ceiling to floor in the bedroom. The smoke layer in the living room had reached a depth of 2.1 m (7′) from the ceiling. Temperature in the corridor remained well stratified.

248 seconds after ignition the researchers cleared the remaining glass from the window to provide a full opening for ventilation. As the glass was removed, the size of the fire in the bedroom and flames exiting the window increased. A thin smoke layer had developed at ceiling level in the target room.

At 300 seconds, flames had begun to burn through the wood, hollow core door to the target room and flaming combustion is also visible in the hallway at the bottom of this door. Flames continued to exit the top 2/3 of the window.

360 seconds into the test, the fire in the bedroom reached steady state (post-flashover), ventilation controlled combustion. The door to the target room has burned through with a dramatic increase in temperature as the room fills with smoke.

Suppression using fixed sprinklers and a hoseline began at 525 seconds.

Fire development during this experiment was not particularly remarkable with conditions that could typically be expected in a residential occupancy. So, what can we learn from this test?

Heat Release Rate

NIST researchers examined the heat release rate of individual fuel packages and combinations of fuel packages prior to the compartment fire tests. These tests conducted in an oxygen consumption calorimeter were performed with the fire in a fuel controlled burning regime. Figure 2 illustrates the heat release rate from the combination of waste container and bed fuel packages and the heat release rate generated during Experiment 1 (in which the initial fuel packages ignited were the waste container and bed located inside the bedroom.

Figure 2. Heat Release Rate Comparison

Note: Adapted from Firefighting Tactics Under Wind Driven Conditions.

Questions: Examine the heat release rate curves in Figure 2 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)?

Temperature

During the experiments temperature was measured in each of the compartments at multiple levels. Figure 3 illustrates temperature conditions in the bedroom at 0.03 m (1″), 1.22 m (4′) and 2.13 m (7′) down from the ceiling during Experiment 1.

Figure 3. Bedroom Temperature

Note: Adapted from Firefighting Tactics Under Wind Driven Conditions. Position.

Questions: Examine the temperature curves in Figure 3 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 2)?
• What happens to the temperature at the upper, mid, and lower levels after around 275 seconds? Why does this happen?

Total Hydrocarbons

In addition to HRR and temperature, researchers measured gas concentrations inside the compartments at the upper and lower levels. Figure 4 shows the concentration (in % volume) of total hydrocarbons in the bedroom and living room. Concentration of total hydrocarbons is a measure of gas phase fuel (pyrolysis products) in the upper layer.

Figure 4. Total Hydrocarbons at the Upper Level

Note: Adapted from Firefighting Tactics Under Wind Driven Conditions. Position.

Questions: Examine the THC curves in Figure 4 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?

The Story Continues…

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

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

The previous post (Shielded Fires) examined US Navy research on the effectiveness of different nozzle techniques when dealing with shielded fires conducted on the ex-USS Shadwell, the US Navy full scale damage control research facility (see Figure 1).

Figure 1. USS Shadwell

The researchers tested two different methods for controlling flaming combustion overhead while moving from the entry point to a location in a compartment where firefighters could make a direct attack on the seat of the fire. The first method involved use of a straight stream or narrow fog pattern and the second involved the use of a medium (60^o) fog pattern directed upward at a 45^o angle. In both cases, one to three second pulses were used in application of water into the hot gas layer.

US Navy Findings

Analysis of this series of tests resulted in identification of a number of specific findings related to tactics, equipment, and training. Three of these findings were particularly relevant to the differences between straight stream/narrow fog and medium fog applied to control flaming combustion in the upper layer.

• Pulsed application with a medium fog pattern directed upward at a 45^o angle resulted in less disruption of the thermal layer than use of a straight stream/narrow fog pattern.
• Use of a straight stream/narrow fog resulted in production of a large amount of steam. This was attributed to the fact that the hose streams had to be deflected compartment linings.
• Water management is important when controlling fire in the upper layer, particularly when using a straight stream/narrow fog. Excess water will only result in excess steam production.

Discussing the findings, the researchers observed that pulsed application of medium fog appeared to be an effective tactic for controlling flaming combustion in the upper layer. This conclusion is supported by consistent reduction of upper layer temperature over the course of the tests involving use of pulsed application of a medium fog pattern.� Previous concerns that this approach would result disruption of thermal layering and excess steam production appeared to be unfounded. This conclusion is supported by the heat flux data at 0.9 M (7′ 10″) and 2.9 M (3′) above the floor. Disruption of thermal layering is indicated by an upward spike in lower level heat flux or equalization of heat flux at the lower and upper levels.

Questions

Several questions about the outcome of these tests were posed at the end of the Shielded Fires post.

• Why did the application of water in a straight stream/narrow fog pattern fail to effectively control flaming combustion in the upper layer?
• Why did the upper layer temperature fluctuate when a straight stream/narrow fog was used?
• Why did the upper layer temperature drop consistently when a medium angle fog pattern was used?
• How did the heat flux measurements correlate with the upper layer temperatures in these two tests?
• What are the implications of the heat flux data recorded during these tests on tenability within the compartment for both firefighters and unprotected occupants?

Water converted to steam on contact with compartment linings or other hot objects cools the surfaces. This indirectly lowers gas layer temperature as the hot gases will continue to transfer heat to compartment linings and other cooler objects in an attempt to equalize temperature. However, the effect on upper layer temperature is limited, minimizing effectiveness of stream application in controlling flaming combustion in the upper layer. In addition, as gas temperature is not significantly reduced, steam produced on contact with hot surfaces is added to the volume of hot gases, resulting in a less tenable environment.

Ineffectiveness of straight stream/narrow fog attack in controlling flaming combustion in the upper layer and the perception of increased steam production with this type of attack likely have a common cause. Conversion of water to steam requires much more energy than simply heating water from ambient temperature to its boiling point. When water changes phase from liquid to gas (steam) while in the hot gas layer, the temperature of the gases is reduced. This has several consequences. First, sufficient reduction in temperature results in extinguishment of flaming combustion. Second, reduction of gas layer temperature causes a proportional reduction in gas volume. As illustrated in Figure 2, if 35% of the water is truned to steam in the hot gas layer, the total volume of steam and hot fire gases is less than the original volume of hot fire gases alone (S�rdqvist, 2002). As this is often difficult to understand, I will provide a more detailed explanation of this in a subsequent post.

Figure 2. Gas Temperature and Relative Volume

Note. Adapted from Water and Other Extinguishing Agents (p. 155) by Stefan S�rdqvist, 2002, Karlstad, Sweden: Raddningsverket. Copyright 2002 by Stefan S�rdqvist and the Swedish Rescue Services Agency.

Production of the same volume of steam can have far different consequences depending on where it is produced (in the hot gas layer versus on contact with hot surfaces!

Total heat flux includes energy transferred through radiation, convection, and conduction. However, in these full scale fire tests, radiant and convective heat transfer was most significant. Radiant heat transfer is dependent on the temperature of upper layer gases and flaming combustion. Convective heat transfer is dependent on gas temperature, movement of hot gases, and moisture. Reduction in upper layer temperature while maintaining thermal layering minimizes total heat flux at the lower level where firefighters are working.

Other Considerations

These tests were conducted on a ship (see Figure 1) with most of the compartment linings being metal (rather than gypsum board, plaster, or wood as typically encountered in buildings. The fire compartment did not have windows or other ventilation openings that may exist in more typical buildings encountered by structural firefighters. These differences are significant, but do not diminish the importance of the results of these tests and findings by the researchers.

These tests provide substantive evidence in support of the effectiveness of water converted to steam in the hot gas layer (as opposed to on surfaces) in controlling flaming combustion in the hot gas layer. However, this does not diminish the importance of direct application of water onto burning fuel in a direct attack to complete the process of extinguishment.

Reference

S�rdqvist, S. (2002). Water and other extinguishing agents. Karlstad, Sweden: Swedish Rescue Services Agency.

Scheffey, J., Siegmann, C., Toomey, T., Williams, F., & Farley J. (1997) 1994 Attack Team Workshop: Phase II-Full Scale Offensive Fog Attack Tests, NRL/MR/6180-97-7944. Washington, DC: United States Navy, Naval Sea Systems Command

Remember the Past

In Myth of the Self-Vented Fire I pointed out that every week represents the anniversary of the death of one or more firefighters as a result of extreme fire behavior. Some firefighters have heard about these incidents, but many have not. In an ongoing 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.

February 11, 1998 – 1030
Firefighter Paramedic Patrick Joseph King
Firefighter Anthony E. Lockhart
Chicago Fire Department, Illinois

Firefighter King and Firefighter Lockhart responded on different companies to a report of a structural fire in a tire shop. No visible fire was encountered, there was no excessive heat, and only light smoke was found in most of the building with heavier smoke in the shop area. Ten firefighters were in the interior of the structure when an event that has been described as a flashover or backdraft occurred. The firefighters were disoriented by the effects of the backdraft. Some were able to escape but Firefighter King and Firefighter Lockhart were trapped in the structure. A garage door that self-operated due to fire exposure may have introduced oxygen into the fire area and may have been a factor in the backdraft. The exit efforts of firefighters were complicated by congestion in the building. Within minutes of the backdraft, the building was completely involved in fire and rescue efforts were impossible. Both firefighters died from carbon monoxide poisoning due to inhalation of smoke and soot. Further information related to this incident can be found in NIOSH Fire Fighter Fatality Investigation 98-F-05.

February 9, 2007
Firefighter-Paramedic Apprentice Racheal Michelle Wilson
Baltimore City Fire Department, Maryland

Firefighter Wilson and the members of her fire academy class were attending a live fire training exercise in a vacant rowhouse in Baltimore.

Firefighter Wilson was assigned to a group of apprentices and an instructor designated as Engine 1. Her group advanced a dry attack line into the structure. As they climbed the stairs, the line was charged. Engine 1 encountered and extinguished fire on the second floor but did not check the rest of the second floor for fire prior to proceeding to the third floor. On the third floor, they again encountered and began to extinguish fire.

Fire conditions began to worsen with a marked increase in smoke and heat that appeared to be coming from the second floor. Engine 1 firefighters who were on the stairs began to receive burns from the fire conditions. The instructor for Engine 1 climbed out a window at the top of the stairs and helped one burned firefighter escape to the roof.

Firefighter Wilson appeared at the window in obvious distress and attempted to escape. The windowsill was unusually high (41 inches) and she was unable to escape. Firefighter Wilson momentarily moved away from the window, at which time she advised other firefighters to go down the stairs to escape. When she returned to the window, her SCBA facepiece was off and she was beginning to receive burns. She was able to get her upper body out of the window but she could not make it through. Firefighters on the exterior were unable to pull her through until firefighters were able to gain access on the interior and assist with the effort.

When Firefighter Wilson was pulled to the roof, she was in full cardiac and respiratory arrest. She was immediately removed from the roof and received advanced life support care and transportation to the hospital. She was pronounced dead at 1250 hours. Firefighter Wilson received total body surface burns of 50 percent. The cause of death was listed as thermal burns and asphyxiation.

Further information related to this incident can be found in NIOSH Firefighter Fatality Investigation F2007-09 and the Independent Investigation Report on the Baltimore City Fire Department Live Fire Training Exercise, 145 South Calverton Road, February 9, 2007.

My next post will examine the incident in which Rachael Wilson lost her life in greater detail.

Ed Hartin, MS, EFO, MIFIreE, CFO

Surprises are Bad!

I frequently observe that surprises on the fireground are bad. Unexpectedly worsening conditions can place firefighters at risk and often result in injuries and fatalities. However, event unexpected success can be problematic, as we don’t know why we were successful (and will likely attribute it to our mastery of the firefighting craft). When we are surprised by fire development or the effectiveness or ineffectiveness of our tactical operations, we really don’t know what is going on! Recognizing critical fire behavior indicators and being able to predict likely fire behavior is a critical skill for firefighters and fire officers at all levels.

B-SAHF: A Systematic Approach

In his paper Reading the Fire Station Officer Shan Raffel of Queensland Fire Rescue observed:

Every fire sends out signals that can assist the firefighter in determining the stage of fire development, and most importantly the changes that are likely to occur. This skill is essential to ensure the correct firefighting strategy and tactics are employed. Being able to “read a fire” is the mark of a firefighter who is able to make decisions based on knowledge and skill, not guess work or luck.

Shan developed a scheme for organizing critical fire behavior indicators that focused on Smoke, Air Track, Heat, and Flame (SAHF). As we worked together in refining this system, I found that one element was missing, the building. Adding building factors that influence fire behavior provides a reasonably comprehensive approach to reading the fire to identify the stage of fire development, burning regime, and likely fire behavior. The simple mnemonic B-SAHF (Building-Smoke, Air Track, Heat, & Flame) can be used to remember this simple approach to reading the fire.

B-SAHF Indicators

The fire behavior indicators should not be considered as a checklist as key indicators will vary with incident conditions. Look at fire behavior indicators from a holistic perspective as illustrated by the following concept map:

Note: This concept map only illustrates the second level of detail in examining the B-SAHF indicators. It is important to extend this map by adding additional detail in each of the categories. For example, in building factors, size may be expanded to include building area and height, number of stories, internal compartmentalization, etc. For a more detailed look at B-SAHF, down load a copy of the full version of B-SAHF Version 5.2.1 in PDF format.

Building: Many aspects of the building (and its contents) are of interest to firefighters. Building construction influences both fire development and potential for collapse. The occupancy and related contents are likely to have a major impact fire dynamics as well.

One of the key factors related to building factors is that they are present before the fire starts. Fire behavior prediction (at least in general terms) should be a key element in pre-incident planning. Look at the building and visualize how a fire would develop and spread based on key building factors.

Smoke: What does the smoke look like and where is it coming from? This indicator can be extremely useful in determining the location and extent of the fire. Smoke indicators may be visible on the exterior as well as inside the building. Don’t forget that size-up and dynamic risk assessment continue after you have made entry!

Air Track: Related to smoke, air track is the movement of both smoke (generally out from the fire area) and air (generally in towards the fire area). Observation of air track starts from the exterior but becomes more critical when making entry. What does the air track look like at the door? Air track continues to be significant when you are working on the interior.

Heat: This includes a number of indirect indicators. Heat cannot be observed directly, but you can feel changes in temperature and may observe the effects of heat on the building and its contents. Remember that you are insulated from the fire environment, pay attention to temperature changes, but recognize the time lag between increased temperature and when you notice the difference. Visual clues such as crazing of glass and visible pyrolysis from fuel that has not yet ignited are also useful heat related indicators.

Flame: While one of the most obvious indicators, flame is listed last to reinforce that the other fire behavior indicators can often tell you more about conditions than being drawn to the flames like a moth. However, that said, location and appearance of visible flames can provide useful information which needs to be integrated with the other fire behavior indicators to get a good picture of conditions.

It is important not to focus in on a single indicator, but to look at all of the indicators together. Some will be more important than others under given circumstances.

Exercising Your Skills

Learning to read the fire takes practice and a solid understanding of practical fire dynamics. This post introduces the concept of B-SAHF and the B-SAHF exercise as a method for improving your skill in reading the fire.

Download and print the B-SAHF Worksheet and then view the first 45 seconds of the following video of an apartment fire in New York City. First, describe what you observe in terms of the Building, Smoke, Air Track, Heat, and Flame Indicators. Second, answer the following five questions:

1. What additional information would you like to have> How could you obtain it?
2. What state(s) of fire development is the fire likely to be in (incipient, growth, fully developed, or decay)? Remember that fire in adjacent compartments can be in a different stage of development?
3. What burning regime is the fire in (fuel or ventilation controlled)?
4. What conditions would you expect to find inside this building?
5. How would you expect the fire to develop over the next two to three minutes

Find more videos like this on firevideo.net

After completing the B-SAHF exercise, view the remainder of the video. Did you successfully predict the fire behavior that occurred? What conditions do you think the firefighters encountered on the interior of the structure?

Now What?

Developing skill in reading the fire requires practice. Additional B-SAHF exercises will be posted on a regular basis at cfbt-us.com. If you have a video clip or photo that you would be willing to share for a B-SAHF exercise, please visit the Contact Us page and send me an e-mail. Also check the CFBT-US Resources page for additional information on Reading the Fire!

Additional Information on Loudoun County Flashover

Previous posts examined an incident in which a number of Loudoun firefighters were injured in a flashover. See Loudoun County Virginia Flashover, Loudoun County Flashover: What Happened, and Loudoun County Flashover: Escape from Floor 2. Several weeks ago Loudoun County Fire, Rescue, & Emergency Management released a presentation including video shot by a civilian bystander during the incident. Print a second copy of the B-SAHF Worksheet and view the Meadowood Court Video, using the worksheet to examine the fire behavior indicators visible from the exterior.

Loudoun County Fire, Rescue, & Emergency Management has also made this video available for download: Meadowood Courth Video Download.

Ed Hartin, MS, EFO, MIFireE, CFO

I recently read an article in the October issue ofFire Engineering magazine titled Improving Preconnect Function and Operation. The author, LT Bob Shovald, described how his department approached the process of improving operations with small, preconnected handlines and focused on three critical factors in effective engine company operations: 1) Hose diameter and flow rate, 2) nozzle selection, and 3) hoseloads. LT Shovald made a number of good points, but misconnected on the basic science behind effective and efficient use of water for fire control.

Flow Rate

LT Shovald makes a case for high flow handlines based on changes in the built environment that influence potential fire behavior.

Primarily it comes down to one important factor, gallons per minute (gpm). Using 95- and 125-gpm attack lines is outdated and dangerous.

• Because of the huge increase of synthetic materials in modern homes and businesses, including foams, plastics, vinyl, and volatile coatings, we are now experiencing fires with higher rates of release than ever before.
• Because of the high cost of energy, more homes and businesses have improved insulation. In a fire, this seals that increased heat inside the structure.
• As a result of more effective fire prevention programs, we arrive on-scene much sooner than in years past, in large part thanks to inexpensive smoke detectors.

What this adds up to is that we are getting on-scene sooner to hotter, more aggressive fires, often just before flashover conditions or self-ventilation. To fight the beast, today we need a bigger gun with bigger bullets (i.e., proving the greater gpm and thus more water faster at the start of our interior attacks). The gpm not the pressure and not the steam kill the beast.

LT Shovald’s argument for high flow handlines sounds reasonable. However, there are a few problems once you look past the surface.

Fire Power vs. Firefighting Power

LT Shovald correctly makes the connection between heat release rate and flow rate necessary for fire control. All too often, firefighters think that it takes “gpm to overcome Btu”�. However, British thermal units (Btu) like Joules (J), are a measure of energy, not its release rate. Heat release rate is expressed in units of energy per unit of time, such as Btu/minute or watts (J/s).

Heat release rate is the most critical factor compartment fire development. If heat release rate is insufficient (e.g., a small fire in a metal trash can) the fire will not flashover or reach the fully developed stage. On the other hand, if the fire involves a recliner or couch, heat release rate is likely to be sufficient for the fire to grow and rapidly transition through flashover to the fully developed stage.

However, there is another critical factor in this scenario. Oxygen is required for the fire to release the chemical potential energy in the fuel. If doors are closed and windows are intact, the fire may quickly consume much of the available oxygen. If this occurs, heat release rate is limited by ventilation and fire growth slows.

LT Shovald states that “it’s the gpm,� not the pressure, and not the steam” that extinguishes the fire. Flow rate is critical, but this is not entirely correct. Water is an excellent extinguishing agent because it has a high specific heat (energy required to raise its temperature) and high latent heat of vaporization (energy required to change it from water to steam). Of these two factors, conversion of water to steam is most significant as it absorbs 7.5 times more energy than heating water from 20^o C ( 68^o F) to its boiling point. The firefighters power is not simply related to flow rate, but flow rate effectively applied to transfer heat from hot gases and surfaces by changing its phase from liquid (water) to gas (steam). Extinguishing a compartment fire generally involves converting a sufficient flow (gpm or lpm) of water to steam. So while the “steam”� itself does not generally extinguish the fire, the energy absorbed in turning the water to steam has the greatest impact on fire extinguishment.

Changes in the Built Environment

LT Shovald is correct that many of the synthetic fuels used in today’s buildings have a higher heat of combustion (potential chemical energy) and given sufficient ventilation have a higher heat release rate when compared to materials such as wood and paper. True to their design, modern, energy efficient buildings retain energy during fire development, speeding the process. However, this type of building also controls normal ventilation (the building is not as “leaky” as older structures) and energy efficient windows are far less likely to fail and change the ventilation profile. As a consequence, the fire department is likely to encounter ventilation controlled fires where heat release rate is limited by the available oxygen. Early detection may also influence fire conditions as firefighters may arrive to find a pre-flashover growth stage fire when heat release has not yet peaked.

The key here is that flow rate must be sufficient to meet or exceed the fires heat release rate. Arriving earlier in the fires growth and building characteristics leading to a ventilation controlled fire, do not necessarily lead to the need for a higher flow rate, on the contrary, the required flow rate during the growth stage is actually lower than that for a fully developed fire (when heat release rate is at its maximum). However, firefighters must also consider potential increase in heat release rate that result from tactical ventilation or unplanned changes in the ventilation profile (e.g., failure of a window).

One excellent point in supporting the argument for high flow handlines that LT Shovald did not raise is the large volume (floor area and ceiling height) and limited compartmentation encountered in many contemporary homes. Older homes generally had smaller rooms and were more highly compartmented. Many new homes have spacious and open floor plans, in some cases with multi-level atriums and high ceilings. In addition to frequently having open floor plans, many of these buildings are also have an extremely large floor area. This type of structure presents a significantly different fire problem and often requires a much higher flow rate than a more traditional, highly compartmented residence.

Tactical Flow Rate

While I agree with LT Shovald regarding the value of high flow handlines, his statement that 95 and 125 gpm are “outdated and dangerous” is unsupported. Safe, effective and efficient fire control requires:

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

A flow rate of 95 or 125 gpm is only dangerous if firefighters attempt to use it to control a fire which requires (or has the potential to require) a higher flow rate. While a high flow rate will quickly extinguish a small fire, this generally results in use of considerably more water as illustrated below.

Effective and efficient fire control requires that we match the flow rate to the task at hand. At the simplest level this means using 1 �”� (38 mm) or 1 �”� (45 mm) handlines for smaller fires and 2″� (50 mm) or 2 �”� (64 mm) handlines for larger fires. It may also mean placing control of flow rate in the nozzle operators hands by using a variable flow or automatic nozzle and letting the firefighter select the flow rate based on the tactical situation.

Ed Hartin, MS, EFO, MIFireE, CFO

Second only to the great solid stream versus fog debate, ventilation strategies seem to create the most discussion and disagreement among fire service practitioners. Vertical or horizontal; natural, negative, or positive pressure; vent before, during or after fire control? These are all good questions (many of which have more than one answer).

The Importance of Why

BC Kriss Garcia recently published an interesting article titled Education vs. Training in Fire Space Control (Fire Engineering, September 2008) examining the difference between training and education, in particular as it relates to ventilation strategies. Kriss emphasized that we train to improve performance and efficiency, but use education to develop our ability to think and understand not only how, but when, why, and why not. Both are critical to today’s firefighters and fire officers.

Space Control

Firefighters sometimes perform ventilation operations by routine, executing tactics simply based on common practice without thought to the influence of these actions on the fire environment and fire behavior. Kriss emphasizes the importance of understanding the effect of changing the ventilation profile and its relationship to fire control, stating:

Absolute control of the space you are opening is necessary for a safe and effective fire attack. If firefighters cannot control the space with enough direct application of [British thermal unit] Btu -quenching water, they should not be opening the space, encouraging additional free burning.

The concepts included in this brief statement are critical, but could be expanded and clarified a bit.

• Developing and maintaining control of the space is critical to offensive firefighting operations and the survival of civilian fire victims who may be trapped in the building.
• Increasing the air supply to a ventilation controlled fire will increase the heat release rate. Heat release rate is measured in kilowatts (kW) or British thermal units (Btu)/m.
• Water application in liters or gallons per minute (lpm or gpm) must exceed the critical rate of flow based on the heat release rate (kW or Btu/min) developed by the fire.

There are two key differences in this expanded outline of the importance of understanding the influence of changing the ventilation profile: 1) Recognizing and understanding the dominant influence on current fire development, fuel or ventilation. Heat release rate from a fire burning in the ventilation controlled burning regime will increase if the fire receives additional air. 2) Water application (lpm or gpm) must be sufficient to overcome the heat release rate from the fire. While it is common to hear firefighters say that gpm must overcome Btu, this is not completely correct. Btu is a measure of energy much the same as liters or gallons is a measure of the volume of water. Kilowatts (1000 joules/second) or Btu/minute are a measure of heat release rate as lpm or gpm are a measure of water application rate.

Tactical ventilation is the other element of space control. Smoke contains unburned pyrolizate and flammable products of incomplete combustion, and as such is fuel. Hot fuel gases overhead can be cooled, providing a buffer zone around the nozzle team, but only when smoke is removed through tactical ventilation is this hazard fully mitigated.

Understanding is Critical

The difficulty that some firefighters have in accepting positive pressure ventilation or positive pressure attack is frequently rooted in a lack of understanding. In some cases, this based on dogmatic attachment to other tactical approaches. In other cases, it is a result of too much training (how to do it) and not enough education (why, why not, and when). Kriss emphasizes the value of positive pressure ventilation and the need to balance training and education to develop both skills proficiency and understanding.

Friendly Criticism

The concluding paragraph of Kriss’s article Education vs. Training in Fire Space Control (Fire Engineering, September 2008) makes two strong statements.

Regardless of the approach we use to safely control fires, we must maintain as the basis of all discussions our ability to control the fire space prior to opening it. The most dramatic means of accomplishing this is through control of the interior environment with [positive pressure attack] PPA and direct water application.

I am fully in agreement with the first sentence. Maintaining control of the fire space is absolutely critical to safe and effective offensive operations. However, the second sentence, which so emphatically supports PPA integrated with direct attack without qualifying the conditions under which this tactic should or should not be used, could be a bit misleading. Under many conditions, PPA and direct attack will be extremely effective. In other circumstances, these tactics are not appropriate. For example, Positive Pressure Attack for Ventilation and Firefighting by Garcia, Kauffmann, and Schelble, identifies several contraindications to use of PPA, inclusive of victims in the exhaust opening or other area which may be threatened and extremely ventilation controlled fire conditions which may present risk of backdraft.

The metaphor of the silver bullet applies to any straightforward solution perceived to have extreme effectiveness. The phrase typically appears with an expectation that some new technology or practice will easily cure a major prevailing problem. (Wikipedia)

In firefighting there are no silver bullets. Increased understanding of the theoretical foundations of fire behavior and the influence of ventilation and applied research such as that done by the National Institute for Standards and Technology are the key to effective use of ventilation strategies and improving the safety and effectiveness of fireground operations.

Firefighters should not uncritically accept current practice. Neither should firefighters accept new or different approaches without the same thoughtful and critical examination. Not just what and how, but why! Kriss’s Positive Pressure Attack website has a wide range of resources related to positive pressure ventilation and positive pressure attack. As Kris advises, both education and training are critical to safe and effective firefighting. Positive pressure attack is an extremely powerful tool when used correctly, be a student of your craft and learn not just what and how, but why!

Kris also published an article titled The Power of Negative Thinking in October issue of FireRescue magazine. This article takes a look at how pressure differences inside and outside the fire building influence ventilation. This interesting article will be the focus of a future post.

Ed Hartin, MS, EFO, MIFireE, CFO

In the Grading the Fireground on a Curve, published in the September issue of Firehouse magazine, Battalion Chief Mark Emery warned of the hazards of assuming that limited volume and velocity of visible smoke indicates a growth stage fire. He correctly identified that compartment fires may enter the decay phase as fuel is consumed or due to a lack of oxygen.

Emery cites National Institute for Occupational Safety and Health (NIOSH) Death in the Line of Duty reports 98-F07 and F2004-14, in which firefighters initiated offensive fire attack in commercial buildings and encountered rapidly deteriorating fire conditions due to changes in the ventilation profile. Concluding the introduction to his article, Emery observes “Unless you know which side of the fire growth curve you are entering, advancing into zero-visibility conditions is really a bad idea”.

I agree with BC Emery’s basic premise that appearances can be deceiving. However, this article points to two interrelated issues. The hazards presented by ventilation controlled fires and the dangerous conditions presented by enclosed buildings. In Smoke Burns,originally published on Firehouse.com I discussed the hazards of ventilation controlled fire and the relationship of burning regime to extreme fire behavior phenomena such as flashover and backdraft. The hazards presented by ventilation controlled fires are compounded when the fire occurs in an enclosed structure (a building with limited means of access and egress). Captain Willie Mora has written extensively on Enclosed Structure Disorientation on Firehouse.com.

BC Emery illustrated how appearances can be deceiving using data and still images from a full scale fire test in a warehouse in Phoenix, Arizona conducted by the National Institute for Standards and Technology (NIST). NIST conducted these tests as part of a research project on structural collapse. However, the video footage and temperature data from this test is extremely useful in studying the influence of ventilation on fire behavior and fire behavior indicators (Building, Smoke, Air Track, Heat, and Flame (B-SAHF)). The full report and video from this test is available on-line from the NIST Building Fire Research Laboratory (BFRL).

As an oxidation reaction, combustion requires oxygen to transform the chemical potential energy in fuel to thermal energy. If a developing compartment fire becomes ventilation controlled, with heat release rate limited by the oxygen available in the compartment, pyrolysis will continue as long as temperature in the compartment is above several hundred degrees Celsius. Pyrolysis products in smoke are gas phase fuel ready to burn. Increased ventilation at this point, may cause the fire to quickly transition to the fully developed stage (ventilation induced flashover). However, if the fire continues to burn in a ventilation controlled state and the concentration of gas phase fuel (pyrolysis products and flammable products of incomplete combustion) increases sufficiently, increased ventilation may result in a backdraft.

I take issue with BC Emery’s illustration of the growth side of the fire development curve as the value side of the cure and the decay side of the curve as the no value side of the curve. Depending on resources, a fire on the growth side of the curve may exceed the offensive fire control capability of the fire department. Conversely, a fire on the decay side of the curve which is limited to a single compartment or series of compartments may be effectively controlled using an appropriate tactics in an offensive strategic mode. However, Emery’s discussion of the more subtle indicators of burning regime that may warn firefighters of a ventilation controlled fire is right on track. For more information on fire behavior indicators and fire development, see Fire Behavior Indicators and Fire Development Parts I and II on Firehouse.com.

Ed Hartin, MS, EFO, MIFireE, CFO

Many firefighters consider Positive Pressure Ventilation (PPV) to be a new tactical approach, despite practical application in the United States since the 1980s. Since its inception, PPV has strong advocates and equally strong opponents. In many cases these opinions sprang from observation of inappropriate application of PPV without a sound understanding of how this tactic actually works. Early on there was little scientific research integrated with practical application of PPV tactics.

However, over the last six years the National Institute of Standards and Technology (NIST) has been conducting an ongoing program of research to identify how PPC works, factors influencing effectiveness in varied applications, and best practices in the application of this tactic. Steve Kerber served as principal investigator on this project. Steve is a fire protection engineer (who also serves as a volunteer Chief Officer in Prince Georges County, Maryland). Steve authored an excellent article titled NIST Goes Back to School published in the September/October issue of NFPA Journal.

This article provides a brief overview of the NIST research on PPV to date and outlines a series of tests conducted in a two-story, 300,000 ft²(27,871 m²) retired high school in Toledo, Ohio, to examine the ability of PPV fans to limit smoke spread or to remove smoke from desired areas in a large low-rise structure.
Steve pointed out the effectiveness of appropriate use of PPV as demonstrated in this series of tests, observing:

In this limited series of experiments the pressure was increased sufficiently to: reduce temperatures, giving potential occupants a more survivable environment and increase fire fighter safety, limit smoke spread, keeping additional parts of the structure safe for occupants and undamaged and reducing the scale of the emergency for the fire fighters, and increase visibility, allowing occupants a better chance to self evacuate and providing fire fighters with an easier atmosphere to operate in. Positive pressure ventilation is a tool the fire service can utilize to make their job safer and more efficient.

However, Steve also provided the following cautionary advice:

Ventilation of oxygen limited or fuel rich fires, either naturally or mechanically, can cause rapid fire growth. Ventilation is not synonymous with cooling. Venting was most effective when coordinated with other operations on the fire ground.

Strong advocates of PPV and positive pressure attack (PPA) such as Battalion Chiefs Kris Garcia and Reinhard Kauffmann, authors of Positive Pressure Attack for Ventilation and Firefighting also caution against use of positive pressure ventilation under extremely ventilation controlled/fuel rich conditions due to backdraft potential.

However, there is no clear line defining when fire conditions are sufficiently ventilation controlled to preclude safe and effective use of positive pressure as a ventilation tactic. Safe and effective use of this tactic requires a sound understanding of practical fire dynamics and the potential influence of tactical operations. This reinforces the ongoing need for scientific research and integration of theory and practical fireground experience in defining best practices in tactical ventilation.

NIST Technical Note 1498, Evaluating Positive Pressure Ventilation in Large Structures: School Pressure and Fire Experiments as well as reports related to NIST’s prior PPV research are available at the Fire.Gov web site. Downloadable video footage is also available for each of these NIST PPV tests.

Ed Hartin, MS, EFO, MIFireE, CFO

Previous posts examined key factors and initial company operations at a residential fire involving flashover that resulted in multiple firefighter injuries at a residential fire in Loudoun County, Virginia. This post will examine the action taken by the trapped firefighters and crews on the exterior.

Reserve Engine 6 was performing fire attack on Floor 2 and Tower 6 had just completed searching the second floor when they experienced a rapid increase in temperature and thickening smoke conditions. Flames were extending from the first floor, up the open foyer and staircase, trapping the two crews on Floor 2.

When the firefighter from Reserve Engine 6 opened the nozzle, the line immediately lost pressure. The engine company officer attempted to diagnose the problem without success. Unknown to the engine crew, the hoseline had partially failed approximately 10′ from the nozzle, drastically reducing the available flow. Lacking an effective stream, the engine crew moved down the hallway towards Bedroom 2 in an attempt to find an alternate means of egress.

Partial collapse of the ceiling separated the Tower 6 firefighter and officer. The firefighter joined up with the crew from Reserve Engine 6 in Bedroom 2. The Tower 6 firefighter partially closed the bedroom door, providing some relief from the increasing temperature. The two firefighters and officer trapped in Bedroom 2 were able to escape over a ladder placed on Side Charlie by the apparatus operator of Reserve Engine 6. It is likely that this quick action by the tower firefighter in closing the door had a significant impact on the tenability of Bedroom 2 for the time required for these three individuals to escape.

Trapped in the Master Bedroom, the officer from Tower 6 attempted to break a window to escape the increasing temperature and thick smoke, but was unable to do so. He exited the master bedroom and eventually escaped through an unspecified window on Floor 2, Side Charlie.

Several factors contributed to the survival of the crews working on floor 2:

• Proper use of personal protective equipment
• Recognition of rapidly deteriorating conditions
• Immediate action to locate an alternate means of egress
• Availability of a secondary egress route provided by the ladders placed by the apparatus operators of the tower and engine
• Closing of the door to Bedroom 2 to increase tenability during emergency egress

Read the report for additional detail on this incident.

The crews of Reserve Engine 6 and Tower 6 who were on Floor 2 had completed survival skills and flashover training. Training and quick reactions contributed to their survival, but increased situational awareness, earlier recognition of developing fire conditions, and control of the fire environment would likely have prevented this accident.

The next post will examine key issues in training focused on “reading smoke” as well as flashover and survival skills training.

Ed Hartin, MS, EFO, MIFireE, CFO

My last post provided an overview of the factors influencing the occurrence of flashover and multiple firefighter injuries at a residential fire in Loudoun County Virginia identified in the report released by Loudoun County Fire, Rescue, and Emergency Management. Let’s look at the events that occurred from the time of dispatch until flashover occurred.

Loudoun County Emergency Communications Center (ECC) dispatched four engines, a truck, rescue, ambulance and two chief officers were dispatched to a reported house fire at 43238 Meadowood Court. The caller reported a fire in the area of the sunroom on the first floor of the home at this address with smoke coming from the roof. Subsequent callers reported heavy smoke in the area. While the call taker received information about the location of the fire in the building, the dispatcher did not pass this information to responding companies.

The first arriving company, Reserve Engine 6 reported that the building was a two-story, single-family dwelling with a fire in the attic or running Side Charlie. Uncertain of the status of building occupants, the engine company officer assigned the truck to perform primary search.

As part of his size-up, the engine company officer walked from Side Alpha around Side Delta to the Charlie/Delta corner to assess conditions. Unfortunately, from this position, he was unable to observe the fire in the area of the sunroom on Floor 1; this factor would become extremely significant over the next seven minutes.

Reserve Engine 6 was staffed with a crew of three, and the firefighter and officer extended a 200′ 1-3/4″ (60.96 M 45 mm) preconnected hoseline to the door on Side Alpha. As the hoseline was being deployed Tower 6, also with a crew of three, arrived on scene and the tower officer and firefighter joined the engine crew at the front door.

When they entered the building, the crews of Reserve Engine 6 and Tower 6 encountered moderately thick smoke and no significant increase in temperature in the two-story (open) foyer. The smoke was thick enough that they had some difficulty in locating the interior staircase. There is no indication that either crew picked up on the presence of significant smoke on Floor 1 as a violation of their expectation of a fire on Floor 2 or in the attic or a potential indicator that there may be a fire on Floor 1.

As they proceeded up the stairs, the crews of Reserve Engine 6 and Tower 6 did not encounter an appreciable change in conditions. Smoke remained moderate, with no significant increase in temperature. Reaching the top of the stairs, the engine crew turned right towards the Master Bedroom. The crew from Tower 6 went left into Bedroom 1 and conducted primary search, venting a window on Side Alpha. The report does not mention if the crew of Tower 6 closed the door to the bedroom while conducting their search or the position of the door when they completed their search of this room and continued to Bedroom 2.

Computer modeling of fire development in this incident has not yet been completed and the report does not indicate that this change in ventilation profile was a significant factor in the occurrence of flashover or extension of flames to Floor 2. However, presence or creation of an air track with crews working between the fire and exhaust opening has been a factor in other incidents. For example, see NIOSH Report 99-F21 and F2000-04 as well as NIST Reports 6854 and 6510.

Entering the master bedroom, the crew of Reserve Engine 6 encountered thick smoke, an increase in temperature, and observed flames on the opposite side of the room (Side Charlie). The officer directed the firefighter to attack the fire while he opened a window on Side Charlie. Tower 6 completed the primary search of Bedroom 2 (no mention of the tower crew making any ventilation openings in Bedroom 2) and then completed a search of Bedroom 3. After finishing the search of Floor 2, the Tower determined the need to pull ceilings for Reserve Engine 6, but doe to the height of the ceiling, did not have tools long enough to accomplish this task.

While crews were working on the interior, the apparatus operator of Tower 6 placed a ladder on Side Alpha to a window in Bedroom 3, removing approximately 2/3 of the glass from the opening. The apparatus operator of Reserve Engine 6 placed a ladder on Side Charlie to a window in Bedroom 2, which broke, but did not remove the glass.

A chief officer arrived and assumed Command on Side Alpha. Command assigned the second chief, who arrived a short time later to perform reconnaissance on Side Charlie. In his transfer of command radio report, the officer of Reserve Engine 6 indicated that the fire was in the attic. Command confirmed that there were flames visible from the attic ridge vents and flames were visible from both sides.

On the interior, the crews of Reserve Engine 6 and Tower 6 experienced a rapid increase in temperature and thickening smoke conditions. The crew of Tower 6, who were exiting to obtain longer tools, encountered flames coming up the open foyer and staircase from the first floor.

MAYDAY, MAYDAY, MAYDAY! Due to a problem with his radio, the tower officer, directed his firefighter to transmit a Mayday message. Concurrently, second arriving chief reported a collapse on Side Charlie.

As with many other incidents resulting in serious injuries or fatalities, this “appeared to be a routine incident”. Companies initiated standard firefighting tactics based on their assessment of incident conditions and the problems presented. The following three events contributed significantly to limited situational awareness:

1. Limited information provided by dispatch
2. Completing a 180^oreconnaissance rather than viewing all sides of the structure
3. Not recognizing key smoke indicators (location, thickness) on Floor 1

While not identified in the report, changing the ventilation profile by opening windows on Floor 2 (possibly based on the assumption that the fire was on Floor 2 or in the attic and the placement of a hoseline by Reserve Engine 6) may have had a negative influence on fire behavior. On the other hand, the placement of ladders to second floor windows by the apparatus operators of the engine and tower provided alternate means of egress for the crews trapped on Floor 2.

Read the report for additional detail on this incident.

The next post will examine the actions taken by Reserve Engine 6 and Tower 6 that aided in their escape from the extreme conditions encountered on Floor 2.

Ed Hartin, MS, EFO, MIFireE, CFO