Posts Tagged ‘reading the fire’

This post continues examination of key indicators used to recognize stages of fire development (i.e., incipient, growth, fully developed, and decay), burning regimes (i.e., fuel and ventilation controlled) with a look at indicators of the fully developed stage of fire development. Most buildings are comprised of multiple, interconnected compartments and fire conditions can vary widely from compartment to compartment. Fire in the compartment of origin may have reached the fully developed stage, while adjacent compartments may have just entered the growth stage.

Figure 1. Fully Developed Fire

National Institute for Occupational Safety and Health (NIOSH) Death in the Line of Duty Report F2007-02 (2009) recommends that fire service agencies: “Train fire fighters to recognize the conditions that forewarn of a flashover/flameover [rollover] and communicate fire conditions to the incident commander as soon as possible” (p. 2). Note: flameover and Rollover are synonyms.

Flameover (Rollover): The condition where unburned fuel (pyrolyzate) from the originating fire has accumulated in the ceiling layer to a sufficient concentration (i.e., at or above the lower flammable limit) that it ignites and burns; can occur without ignition of, or prior to, the ignition of other fuels separate from the origin. (NFPA 921, 2008, 3.3.67 and 3.3.137)

Recognition of key fire behavior indicators is critical. However, communication of this information to the incident commander (as it may impact on strategies) alone is not sufficient. Companies working in the fire environment must proactively mitigate this threat through effective fire control and ventilation strategies and tactics.

Flashover

Flashover is the sudden transition from a growth stage to fully developed fire. When flashover occurs, there is a rapid transition to a state of total surface involvement of all combustible material within the compartment. Conditions for flashover are defined in a variety of different ways. In general, ceiling temperature in the compartment must reach 500^o-600^o C (932^o-1112^o F) or the heat flux (a measure of heat transfer) to the floor of the compartment must reach 15-20 kW/m² (1.32 Btu/s/ft²)-1.76 Btu/s/ft²). When flashover occurs, burning gases will push out openings in the compartment (such as a door leading to another room) at a substantial velocity (Karlsson & Quintiere, 2000).

It is important to remember that flashover does not always occur. There must be sufficient fuel and oxygen for the fire to reach flashover. If the initial object that is ignited does not contain sufficient energy (heat of combustion) and does not release it quickly enough (heat release rate), flashover will not occur (e.g., small trash can burning in the middle of a large room). Likewise, if the fire sufficiently depletes the available oxygen, heat release rate will drop and the fire in the compartment will not reach flashover (e.g., small room with sealed windows and the door closed). A fire that fails to reach a sufficient heat release rate for flashover to occur due to limited ventilation presents a significant hazard as increased ventilation may result in a ventilation induced flashover (see Understanding Flashover: Myths & Misconceptions Part 2 and The Ventilation Paradox).

Indicators of Flashover Potential

Recognizing flashover and understanding the mechanisms that cause this extreme fire behavior phenomenon is important. However, the ability to recognize key indicators and predict the probability of flashover is even more important. Indicators of potential or impending flashover are listed in Figure 2.

Figure 2. Indicators of Potential Flashover

If the fire in our residential scenario is nearing flashover (in the compartment of origin) what fire behavior indicators might be observed? Use the B-SAHF model to help you frame your answers.

You have responded to a fire in a one-story single family dwelling of wood frame construction. A fire which started in a bedroom on the Alpha Bravo corner of the structure is nearing flashover. A thick hot gas layer has developed in the bedroom and is flowing out the open door into the hallway. The fire has extended to the bed and flames in the plume have reached the ceiling and have begun to extend horizontally in the ceiling jet. Fuel packages below the level of the hot gas layer (e.g., furniture, carpet, and contents) are beginning to pyrolize.

• What conditions would you expect to see from the exterior of the structure?
• What indicators may be visible from the front door as you make entry?

Remember that fire conditions will vary throughout the building. While the fire is in the growth stage and nearing flashover in the bedroom, conditions may be different in other compartments within the building.

• What indicators would you anticipate observing as you traveled through the living room to the hallway leading to the bedroom?
• What conditions would you find in the hallway outside the fire compartment?
• After making entry, consider if conditions are different than you anticipated?
• Why might this be the case?
• What differences in conditions would be cause for concern?
• How might your answers to the preceding questions have differed if the bedroom door was closed and fire growth limited by ventilation?

Fully Developed Fire

At this post-flashover stage, energy release is at its greatest, but is generally limited by ventilation (more on this in a bit). Unburned gases accumulate at the ceiling level and frequently burn as they leave the compartment, resulting in flames showing from doors or windows. The average gas temperature within a compartment during a fully developed fire ranges from 700^o-1200^o C (1292^o-2192^o F)

Remember that the compartment where the fire started may reach the fully developed stage while other compartments have not yet become involved. Hot gases and flames extending from the involved compartment transfer heat to other fuel packages (e.g., contents, compartment linings, and structural materials) resulting in fire spread. Conditions can vary widely with a fully developed fire in one compartment, a growth stage fire in another, and an incipient fire in yet another. It is important to note that while a fire in an adjacent compartment may be incipient, conditions within the structure are immediately dangerous to life and health (IDLH).

Indicators of a Fully Developed Fire

Remember that a fully developed fire refers to conditions within a given compartment or compartments. It does not necessarily mean that the entire building is fully involved. Figure 3 lists indicators of fully developed fire conditions.

Figure 3. FBI-Fully Developed Stage

If the fire in our residential scenario has progressed to the fully developed stage (in the compartment of origin) what fire behavior indicators might be observed? Use the B-SAHF model to help you frame your answers.

You have responded to a fire in a one-story single family dwelling of wood frame construction. A fire which started in a bedroom on the Alpha Bravo corner of the structure has reached the fully developed stage and now involves the contents of the room and interior finish of this compartment.

• What conditions would you expect to see from the exterior of the structure?
• What indicators may be visible from the front door as you make entry?

Remember that fire conditions will vary throughout the building. While the fire is fully developed in the bedroom, conditions may be different in other compartments within the building.

• What indicators would you anticipate observing as you traveled through the living room to the hallway leading to the bedroom?
• What conditions would you find in the hallway outside the fire compartment?
• After making entry, consider if conditions are different than you anticipated?
• Why might this be the case?
• What differences in conditions would be cause for concern?

Ventilation Controlled Fires

When the fire is burning in a ventilation controlled state, any increase in the supply of oxygen to the fire will result in an increase in heat release rate. Increase in ventilation may result from firefighters making entry into the building (the access point is a ventilation opening), tactical ventilation (performed by firefighters), or unplanned ventilation (e.g., failure of window glazing due to elevated temperature).

It is essential to recognize when the fire is, or may be ventilation controlled, and the influence of planned and unplanned changes in ventilation profile on fire behavior. Most compartment fires in the late growth stage or which are fully developed are ventilation controlled when the fire department arrives. Even if the fire has not entered the decay stage due to limited ventilation, the increased oxygen provided by increases in ventilation (such as that caused by opening the door to make entry) will increase heat release rate. This is not to say that increased ventilation is a bad thing, but firefighters should be prepared to deal with this change in fire behavior.

Remember the Past

Line of duty deaths involving extreme fire behavior has a significant impact on the family of the firefighter or firefighters involved as well as their department. Department investigative reports and NIOSH Death in the Line of Duty reports point out lessons learned from these tragic events. However, as time passes, these events fade from the memory of those not intimately connected with the individuals involved. It is important that we remember the lessons of the past as we continue our study of fire behavior and work to improve firefighter safety and effectiveness on the fireground.

October 29, 2008
Firefighter Adam Cody Renfroe
Crossville Fire Department, Alabama

The Crossville Fire Department was dispatched to a fire in a single-family residence. was on the first engine to arrive on the scene to find thick, black smoke from the roof and a report that all occupants were out of the house.

Firefighter Renfroe and another firefighter advanced a hoseline to the front door of the residence. He sent the other firefighter back to the fire truck for a tool. When the firefighter returned, Firefighter Renfroe was gone and the nozzle remained by the doorway. At about the same time, the fire inside of the structure intensified. Firefighter Renfroe transmitted a distress message from the interior. Firefighters were not immediately able to enter the structure due to fire conditions.

Firefighters discovered Firefighter Renfroe about 4 feet from the home’s back door, but By the time firefighters reached him, he was deceased. The cause of death was smoke inhalation and thermal burns.

For more information on this incident, see NIOSH Death in the Line of Duty Report F2008-34.

Ed Hartin, MS, EFO, MIFireE, CFO

References

Karlson, B. & Quintiere, J. (2000) Enclosure fire dynamics. Boca Raton, FL: CRC Press.

National Institute for Occupational Safety and Health (NIOSH). (2009). Death in the Line of Duty Report F2007-02. Retrieved October 22, 2009 from http://www.cdc.gov/niosh/fire/pdfs/face200702.pdf .

Open Enrollment CFBT Level I & Instructor Courses

CFBT-US, LLC and the Northwest Association of Fire Trainers (NAFT) will be offering CFBT Level I and Instructor Courses at the Clackamas County (OR) Fire District I CFBT facility.

CFBT Level I
7-9 November 2009
Course Fee: $335

CFBT Instructor
9-13 November 2009
Course Fee: $915

Instructor course participants receive a copy of 3D Firefighting: Training, Techniques, & Tactics and an extensive 2-DVD library of CFBT resources including the CFBT Level I curriculum. For information on these courses download a NAFT CFBT Brochure and the CFBT Level I and CFBT Instructor Course Information Sheets.

CFBT Workshop in Sandö, Sweden

From 12-16 October 2009, I will be participating in a CFBT workshop in Sandö, Sweden along with a small group of instructors from around the world. We will be studying the compartment fire behavior curriculum at the Swedish Civil Contingencies Agency (Myndigheten för samhällsskydd och beredskap (MSB)) College in Sandö.

Figure 1. Fire Behavior Training in Sandö

In January of 2009 MSB replaced the Swedish Rescue Services Agency, the Swedish Emergency Management Agency, and the Swedish National Board of Psychological Defense. The MSB maintains two fire service colleges, one in Sandö (see Figure 2) and the other in Revinge.

Figure 2. MSB College in Sandö

The International Conference of Fire and Rescue, Valdivia – Chile 2010 CIFR

My brothers with Company 1 “Germania” of the Valdivia, Chile Fire Department have taken on a tremendous task with delivery of the first International Conference of Fire & Rescue in Valdivia. The conference will be held 23-27 January 2010.

Conference presenters include a diverse cadre of instructors from around the world. I will be presenting a series of seminars on fire behavior as well as a hands-on CFBT workshop. Presentations will be simultaneously translated into English and Spanish (as applicable). Have a look at the Conference Web Site for more information on this tremendous learning opportunity.

NIOSH Death in the Line of Duty F2007-02

On November 23, 2006, Firefighter Steven Solomon, a 33-year-old career fire fighter was seriously injured during a ventilation induced flashover or related fire behavior event in an abandoned single story duplex in Atlanta, GA; he died as a result of these injuries 6 days later.

NOSH Report F2007-02 provides an excellent description of fire behavior indicators observed prior to the occurrence of extreme fire behavior and correctly identifies that increased ventilation without coordinated fire attack resulted in worsening fire conditions.

Several conclusions in the report were based on computational fluid dynamics (CFD) modeling using the National Institute of Standards and Technology (NIST) Fire Dynamics Simulator software. As discussed in a previous post computer modeling is an excellent tool, but it is important to understand both its capabilities and limitations (see Townhouse Fire-Washington, DC: Computer Modeling)

It is crucial to bear in mind that fire models do not provide a reconstruction of the reality of an event. They are simplified representation of reality that will always suffer from a certain lack of accuracy and precision. Under the condition that the user is fully aware of this status and has an extensive knowledge of the principles of the models, their functioning, their limitations and the significance attributed to their results, fire modeling becomes a very powerful tool (Dele´mont & Martin, J., 2007, p. 134).

Review NIOSH Report F2007-02 and see if you agree or disagree with the conclusions regarding the type of extreme fire behavior phenomena involved in this incident.

Ed Hartin, MS, EFO, MIFireE, CFO

Chicago Dollar Store Fire

On the morning of October 1, 2009 the Chicago Fire Department (CFD) responded to a fire in the Super Dollar and Up store at 3952 West Cermak Road. CFD Senior Fire Alarm Operator and Fire Photographer Steve Redick captured early incident operations on video.

The first segment of the video was shot in the alley on Side C from the B/C Corner. The next several minutes of video are shot from positions on Side A as indicated in Figure 1.

Figure 1. Plot Plan and Approximate Video Camera Locations

Download the B-SAHF Worksheet.

Watch the first 60 seconds of Video Segment 1. Consider the information provided in this segment of the video clip. First, describe what you observe in terms of the Building, Smoke, Air Track, Heat, and Flame Indicators and then answer the following five standard questions?

1. What additional information would you like to have? How could you obtain it?
2. What stage(s) of development is the fire likely to be in (incipient, growth, fully developed, or decay)?
3. What burning regime is the fire in (fuel controlled 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?

After completing the B-SAHF worksheet and answering the five standard questions, watch the next minute and twenty seconds of the video.

1. Did you anticipate this change?
2. What factors may have influenced this change in conditions?

Visit Steve Redick’s Web Site for additional video and excellent photos of this incident.

Memphis Dollar Store LODD

The rapidly changing conditions in the Chicago incident reminded me of the fire in Memphis, Tennessee that took the lives of Lieutenant Trent Kirk and Private Charles Zachary. Similar to the fire in Chicago, this incident involved a fire in a one-story, non-combustible building containing multiple commercial occupancies. As companies arrived they observed a small volume of smoke from the roof and little smoke inside the building. Approximately nine minutes after arrival conditions worsened with a large volume of smoke pushing from the doorway on Side A. Crews became disoriented as a result of rapid fire progression, and Lieutenant Kirk and Private Zachary were trapped.

For additional information on this incident see NIOSH Death in the Line of Duty Report F2003-18 and Memphis Fire Department Director’s Review Board Family Dollar Store Fire report.

Dollar Stores as a Target Hazard

Dollar stores and similar types of commercial occupancies should be considered as a target hazard that presents a significant threat to firefighters. These types of stores are generally in an enclosed building (good access from the front, but not generally from the other sides of the building) with high ceilings and a cockloft or other ceiling void space. In addition, this type of store contains a large fuel load comprised predominantly of synthetic fuel with a high heat of combustion (think high energy) and potential for extremely rapid fire development.

Fires in this type of occupancy are not uncommon! A quick search uncovered 15 similar incidents across the United States in the last three years (and 11 in 2009). There were likely more (as the scope of this search looked for fires in “dollar stores” and stopped after the first several hundred hits with the Google search engine).

• Broadview, IL (June 9, 2009)
• Flint, MI (August 24, 2009)
• Lubbock, TX (September 15, 2009)
• Terre Haute, IN (June 29, 2009)
• New York, NY (June 9, 2009)
• Midlothian, IL (February 6, 2008)
• Highland Park, MI (October 7, 2007)
• Denver, CO (June 29, 2009)
• Sanford, FL (March 23, 2009)
• Chattanooga, TN (April 14, 2009)
• Conklin, NY (August 27, 2009)
• Muncie, IN (September 16, 2009)
• Lake Worth, TX (November 25, 2006)
• Omaha, NE (April 8, 2008)
• Bells Corner, PA (June 3, 2009)

Building Factors and Fire Behavior

Building factors include the construction, configuration, and contents of a structure. These factors are critical fire behavior indicators that must be assessed during pre-planning and in the course of size-up and incident operations. Consider how building size (particularly volume, ceiling height, and presence of ceiling, attic, or cockloft void spaces) impacts on both fire behavior and how the other B-SAHF indicators present.

Reporting on the Dollar Store fire in Chattanooga, TN in April 2009, a Chattanooga Fire Department spokesperson said:

At first, it appeared that the firefighters would be able to get the fire under control fairly quickly, but the fire got into the attic and was difficult to locate in the thick, black smoke… The firefighters made an interior attack and tried to use thermal imaging cameras to locate the fire. However, other firefighters noticed that the roof was beginning to sag, so the order was given to evacuate the building for the safety of the firefighters.

It is essential to recognize potential for worsening conditions and extreme fire behavior. This is particularly important when faced with an incident outside the norm of fires in residential structures such as one and two-family dwellings and apartments.

Posts from Sandö, Sweden

Next week I will be posting from Sandö, Sweden as 12-16 October I will be participating in a Compartment Fire Behavior Training Workshop at the Swedish Civil Contingencies Agency College. Along with representitives from Australia, Canada, Germany, and Spain, I will be studying contemporary approaches to fire behavior training as well as the evolution of Swedish fire behavior training since the 1980s. This workshop provides a tremendous opportunity to learn along with Mats Rosander, Nils Bergström, and Marcos Dominguez, poneers in the evolution of fire behavior training in Sweden and around the world.

Ed Hartin, MS, EFO, MIFIreE, CFO

This post continues study of an incident in a townhouse style apartment building in Washington, DC with examination of the extreme fire behavior that took the lives of Firefighters Anthony Phillips and Louis Mathews. As discussed in Townhouse Fire: Washington, DC-Computer Modeling Part I, this was one of the first cases where the NIST Fire Dynamics Simulator (FDS) software was used in forensic fire scene reconstruction (Madrzykowski and Vettori, 2000).

Quick Review

As discussed in prior posts, crews working on Floor 1 to locate the fire and secure the door to the stairwell were trapped and burned as a result of rapid progression of a fire in the basement up the open interior stairway after an exterior sliding glass door was opened to provide access to the basement. For detailed examination of incident operations and fire behavior, see:

• Fire Behavior Case Study Townhouse Fire: Washington, DC
• Townhouse Fire: Washington DC-What Happened
• Townhouse Fire: Washington DC-Extreme Fire Behavior
• Townhouse Fire: Washington DC-Computer Modeling

Figure 1. Conditions at Approximately 00:28

Note: From Report from the Reconstruction Committee: Fire at 3146 Cherry Road NE, Washington DC, May 30, 1999, p. 29 & 32. District of Columbia Fire & EMS, 2000.

Smokeview

Smokeview is a visualization program used to provide a graphical display of a FDS model simulation in the form of an animation or snapshot. Snapshots illustrate conditions in a specific plane or slice within the building. Three vertical slices are important to understanding the fire dynamics involved in the Cherry Road incident: 1) midline of the door on Floor 1, Side A, 2) midline of the Basement Door, Side C, and midline of the Basement Stairwell (see Figure 2). Imagine that the building is cut open along the slice and that you can observe the temperature, oxygen concentration, or velocity of gas movement within that plane.

Figure 2. Perspective View of 3146 Cherry Road and Location of Slices

Note: From Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999, NISTR 6510 (p. 15) by Dan Madrzykowski and Robert Vettori, 2000, Gaithersburg, MD: National Institute for Standards and Technology.

In addition to having an influence on heat release rate, the location and configuration of exhaust and inlet openings determines air track (movement of smoke and air) and the path of fire spread. In this incident, the patio door providing access to the basement at the rear acted as an inlet, providing additional air to the fire. The front door and windows on the first floor opened for ventilation served as exhaust openings and provided a path for fire travel when the conditions in the basement rapidly transitioned to a fully developed fire.

Figures 3-10 illustrate conditions at 200 seconds into the simulation, which relates to approximately 00:27 during the incident, the time at which the fire in the basement transitioned to a fully developed stage and rapidly extended up the basement stairway to Floor 1. Data is presented as a snapshot within a specific slice. Temperature and velocity data are provide for each slice (S1, S2, & S3 as illustrated in Figure 2).

Figure 3. Temperature Along Centerline of Basement Door Side C (S1) at 200 s

Note: From Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999, NISTR 6510 (p. 17) by Dan Madrzykowski and Robert Vettori, 2000, Gaithersburg, MD: National Institute for Standards and Technology.

Figure 4. Vector Representation of Velocity Along Centerline of Basement Door Side C (S1) at 200 s

Note: From Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999, NISTR 6510 (p. 18) by Dan Madrzykowski and Robert Vettori, 2000, Gaithersburg, MD: National Institute for Standards and Technology.

Figure 5. Oxygen Concentration Along Centerline of Basement Door Side C (S1) at 200 s

Note: From Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999, NISTR 6510 (p. 23) by Dan Madrzykowski and Robert Vettori, 2000, Gaithersburg, MD: National Institute for Standards and Technology.

Figure 6. Temperature Slice Along Centerline of Basement Stairwell (S2) at 200 s

Note: From Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999, NISTR 6510 (p. 21) by Dan Madrzykowski and Robert Vettori, 2000, Gaithersburg, MD: National Institute for Standards and Technology.

Figure 7. Vector Representation of Velocity Along Centerline of Basement Stairwell (S2) at 200 s

Note: From Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999, NISTR 6510 (p. 22) by Dan Madrzykowski and Robert Vettori, 2000, Gaithersburg, MD: National Institute for Standards and Technology.

Figure 8. Oxygen Concentration Along Centerline of Basement Stairwell (S2) at 200 s

Note: From Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999, NISTR 6510 (p. 24) by Dan Madrzykowski and Robert Vettori, 2000, Gaithersburg, MD: National Institute for Standards and Technology.

Figure 9. Temperature Slice Along Centerline of Floor 1 Door Side A (S3) at 200 s

Note: From Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999, NISTR 6510 (p. 19) by Dan Madrzykowski and Robert Vettori, 2000, Gaithersburg, MD: National Institute for Standards and Technology.

Figure 10. Vector Representation of Velocity Along Centerline of Floor 1 Door Side A (S3) at 200 s

Note: From Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999, NISTR 6510 (p. 20) by Dan Madrzykowski and Robert Vettori, 2000, Gaithersburg, MD: National Institute for Standards and Technology.

Figure 11. Perspective Cutaway, Flow/Temperature, Velocity, and O₂ Concentration

Figure 12. Thermal Exposure Limits in the Firefighting Environment

Note: Adapted from Measurements of the firefighting environment. Central Fire Brigades Advisory Council Research Report 61/1994 by J.A. Foster & G.V. Roberts, 1995. London: Department for Communities and Local Government and Thermal Environment for Electronic Equipment Used by First Responders by M.K. Donnelly, W.D. Davis, J.R. Lawson, & M.J. Selepak, 2006, Gaithersburg, MD: National Institute of Standards and Technology.

Compartment Fire Thermal Hazards

The temperature of the atmosphere (i.e., smoke and air) is a significant concern in the fire environment, and firefighters often wonder or speculate about how hot it was in a particular fire situation. However, gas temperature in the fire environment is a bit more complex than it might appear on the surface and is only part of the thermal hazard presented by compartment fire.

Tissue temperature and depth of penetration determine the severity of a thermal burn. Temperature and penetration are dependent on the amount of energy absorbed and the duration of the thermal insult as well as the properties of human tissue. In a compartment fire, firefighters absorb energy from any substance that has a temperature above 37^o C (98.6^o F), including hot compartment linings, contents, the hot gas layer, and flames. The dominant mechanisms of heat transfer involved in this process are convection and radiation (although conduction through personal protective equipment is also a factor to be considered).

The total thermal energy received is described in joules per unit area. However, the speed or rate of energy is transferred may be more important when assessing thermal hazard. Heat (thermal) flux is used to define the rate of heat transfer and is expressed in kW/m² (Btu/hr/ft²).

One way to understand the interrelated influence of radiant and convective heat transfer is to consider the following scenario. Imagine that you are standing outside in the shade on a hot, sunny day when the temperature is 38^o C (100^o F). As the ambient temperature is higher than that of your body, energy will be transferred to you from the air. If you move out of the shade, your body will receive additional energy as a result of radiant heat transfer from the sun.

Convective heat transfer is influenced by gas temperature and velocity. When hot gases are not moving or the flow of gases across a surface (such as your body or personal protective equipment) is slow, energy is transferred from the gases to the surface (lowering the temperature of the gases, while raising surface temperature). These lower temperature gases act as an insulating layer, slowing heat transfer from higher temperature gases further away from the surface. When velocity increases, cooler gases (which have already transferred energy to the surface) move away and are replaced by higher temperature gases. When velocity increases sufficiently to result in turbulent flow, hot gases remain in contact with the surface on a relatively constant basis, increasing convective heat flux.

Radiant heat transfer is influenced by proximity and temperature of the radiating body. Radiation increases by a factor of four when distance to the hot material is reduced by half. In addition, radiation increases exponentially (as a function of the fourth power) as absolute temperature increases.

Thermal hazard may be classified based on hot gas temperature and radiant heat flux (Foster & Roberts, 1995; Donnelly, Davis, Lawson, & Selpak, 2006) with temperatures above 260^o C (500^o F) and/or radiant heat flux of 10 kW/m² (3172 Btu/hr/ft²) being immediately life threatening to a firefighter wearing a structural firefighting ensemble (including breathing apparatus). National Institute of Standards and Technology (NIST) experiments in a single compartment show post flashover gas temperatures in excess of 1000^o C (1832^o F) and heat flux at the floor may exceed 170 kW/m² (Donnelly, Davis, Lawson, & Selpak, 2006). Post flashover conditions in larger buildings with more substantial fuel load may be more severe!

Figure 11 integrates temperature, velocity, and oxygen concentration data from the simulation (Figures 3-10). Detail and accuracy is sacrificed to some extent in order to provide a (somewhat) simpler view of conditions at 200 seconds into the simulation (approximately 00:27 incident time). Note that as in individual slices, data is presented as a range due to uncertainty in the computer model.

Alternative Model

In addition to modeling fire dynamics based on incident conditions and tactical operations as they occurred, NIST also modeled the incident with a slightly different ventilation profile.

The basic input for the alternate simulation was the same as the simulation of actual incident conditions. Ventilation openings and timing was the same, with one exception; the sliding glass door on Floor 1, Side C was opened at 120 s into the simulation. Conditions in the basement during the alternative simulation were similar to the first. However, on Floor 1, the increase in ventilation provided by the sliding glass door on Side C resulted in a shallower hot gas layer and cooler conditions at floor level. A side-by-side comparison of the temperature gradients in these two simulations is provided in Figure 13.

Figure 13. Comparison of Temperature Gradients Along Centerline of Basement Stairwell (S2) at 200 s

Note: Adapted from Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999, NISTR 6510 (p. 21 & 27) by Dan Madrzykowski and Robert Vettori, 2000, Gaithersburg, MD: National Institute for Standards and Technology.

The NIST Report (Madrzykowski & Vettori, 2000) identified that the significant difference between these two simulations is in the region close to the floor. In the alternative simulation (Floor 1, Side C Sliding Glass Door Open) between the doorway to the basement and the sofa, the temperatures from approximately 0.6 m (2 ft) above the floor, to floor level are in the range of 20 °C to 100 °C (68°F to 212 °F), providing at least an 80 °C (176 °F) temperature reduction.

While this is a considerable reduction in gas temperature, it is essential to also consider radiant heat flux from the hot gas layer. Given the temperature of the hot gases from the ceiling level to a depth of approximately 3′ (0.9 m), the heat flux at the floor would likely have been in the range of 15-20 kW/m² (or greater).

Questions

1. Temperatures vary widely at a given elevation above the floor. Consider the slices illustrated in Figures 3, 6, and 9, and identify factors that may have influenced these major differences in temperature.
2. How might the variations in temperature illustrated in Figures 3, 6, and9 and location of Firefighters Phillips (basement doorway), Mathews (living room, C/D corner), and Morgan (between Phillips & Mathews) have influenced their injuries?
3. Examine the velocity of gas movement illustrated in Figures 4, 7, and 10 and integrated illustration conditions in Figure 11. How does this correlate to the photos in Figure 1 illustrating incident conditions at approximately 00:28?
4. Explain how the size and configuration of ventilation openings resulted in a bi-directional air track at the basement door on Side C.
5. How did the velocity of hot gases in the stairwell and living room influence the thermal insult to Firefighters Phillips, Mathews, and Morgan? What factors caused the high velocity flow of gases from the basement stairwell doorway into the living room?
6. Rescue 1B noted that the floor in the living room was soft while conducting primary search at approximately 00:30. Why didn’t the parallel chord trusses in the basement fail sooner? Is there a potential relationship between fire behavior and performance of the engineered floor support system in this incident?
7. How might stability of the engineered floor support system have differed if the sliding glass door in the basement had failed prior to the fire departments arrival? Why?
8. How might the double pane glazing on the windows and sliding glass doors have influenced fire development in the basement? How might fire development differed if these building openings had been fitted with single pane glazing?
9. What was the likely influence of turbulence in the flow of hot gases and cooler air on combustion in the basement? What factors influenced this turbulence (examine Figures 4, 7, and 10) illustrating velocity of flow and floor plan illustrated in conjunction with the second question)?
10. How did conditions in the area in which Firefighters Phillips, Mathews, and Morgan were located correlate to the thermal exposure limits defined in Figure 12? How did this change in the alternate scenario? Remember to consider both temperature and heat flux.

Extended Learning Activity

The Cherry Road case study provides an excellent opportunity to develop an understanding of the influence of building factors, burning regime, ventilation, and tactical operations on fire behavior. These lessons can be extended by comparing and contrasting this case with other cases such as the 1999 residential fire in Keokuk, Iowa that took the lives Assistant Chief Dave McNally, Firefighter Jason Bitting, and Firefighter Nathan Tuck along with three young children. For information on this incident see NIOSH Death in the Line of Duty Report F2000-4, NIST report Simulation of the Dynamics of a Fire in a Two Story Duplex, NIST IR 6923.and video animation of Smokeview output from modeling of this incident

Ed Hartin, MS, EFO, MIFireE, CFO

References

District of Columbia (DC) Fire & EMS. (2000). Report from the reconstruction committee: Fire at 3146 Cherry Road NE, Washington DC, May 30, 1999. Washington, DC: Author.

Madrzykowski, D. & Vettori, R. (2000). Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999, NISTR 6510. August 31, 2009 from http://fire.nist.gov/CDPUBS/NISTIR_6510/6510c.pdf

National Institute for Occupational Safety and Health (NIOSH). (1999). Death in the line of duty, Report 99-21. Retrieved August 31, 2009 from http://www.cdc.gov/niosh/fire/reports/face9921.html

The last post in this series, Incipient Fires: Key Fire Behavior Indicators reviewed stages of fire development (i.e., incipient, growth, fully developed, and decay), burning regimes (i.e., fuel and ventilation controlled) and identified key indicators used to recognize incipient stage fires. This post examines key indicators to identify growth stage fires and their burning regime.

Growth Stage & Burning Regime

Like many concepts in fire dynamics there is a bit of ambiguity between where the incipient stage ends and the growth stage begins. For firefighters, this distinction is important as growth stage fires are deemed to present an Immediately Dangerous to Life and Health (IDLH) threat based on the increasing speed of fire development, toxicity and thermal environment. This triggers Occupational Safety and Health Administration (OSHA) respiratory protection regulations requirements for “two-in/two-out”. Key characteristics of a growth stage fire include increasing heat release rate (HRR), significantly increasing temperature within the compartment.

The speed of fire development in the growth stage may be limited by fuel characteristics and configuration or ventilation. Typically compartment fires in the early growth stage are fuel controlled. However, if the compartment is small and/or has limited ventilation, continued combustion will result in slowing fire development as the fire enters the ventilation controlled burning regime. Recognizing the ventilation controlled burning regime is critical as increases in ventilation will result in increased HRR. This is not necessarily a major problem unless it is unanticipated or firefighters do not have the capacity to control this additional HRR.

A Single Compartment

While most buildings have multiple, interconnected rooms, providing a complex environment for fire development, it is useful to begin by examining fire development in a single compartment (see Figure 1)

Figure 1. Fire Development in a Single Compartment.

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

As a compartment fire develops hot products of combustion and entrained air rise in a plume from the burning fuel package. When the plume reaches the ceiling, hot gases begin to move horizontally, forming a ceiling jet. As the fire progresses through the incipient stage and into growth, additional fuel will become involved and the heat release rate from the fire will increase. While thermal conditions can be considerably more complex, gas temperatures within the compartment may be described as existing in two layers: A hot layer extending down from the ceiling and a cooler layer down towards the floor. Convection resulting from plume and ceiling jet along with radiant heat from the fire and hot particulates in the smoke increases the temperature of the compartment linings and other items in the compartment.

The fire can continue to grow through flame spread or by ignition of other fuel within the compartment. As flames in the plume reach the ceiling they will bend and begin to extend horizontally. Pyrolysis products and flammable byproducts of incomplete combustion in the hot gas layer will ignite and continue this horizontal extension across the ceiling. As the fire moves further into the growth stage, the dominant heat transfer mechanism within the fire compartment shifts from convection to radiation. Radiant heat transfer increases heat flux (transfer of thermal energy) at floor level.

As gases within the compartment are heated they expand and when confined by the compartment increase in pressure. Higher pressure in this layer causes it to push down within the compartment and out through openings. The pressure of the cool gas layer is lower, resulting in inward movement of air from outside the compartment. At the point where these two layers meet, as the hot gases exit through an opening, the pressure is neutral. The interface of the hot and cool gas layers at an opening is commonly referred to as the neutral plane.

If the compartment is sealed (e.g., door closed and windows intact), the fire may become ventilation controlled, slowing the increase in HRR and temperature, and eventually moving the fire into the decay stage (defined by decreasing HRR). However, if the compartment is not sealed (e.g., open door), the fire may become ventilation controlled, but HRR can continue to increase as smoke flows out of the involved compartment and air from the remainder of the building flows in at floor level, providing the oxygen necessary for continued combustion.

In growth stage fires, fire behavior indicators are often visible from the exterior of the building. However, depending on fire location and building factors (e.g., energy efficiency, ventilation profile) these indicators may be fairly obvious or quite subtle. Growth stage indicators are listed in Figure 2

Figure 2. FBI: Growth Stage

In Incipient Fires: Key Fire Behavior Indicators you were presented with a residential fire scenario as an opportunity to give some thought to how key fire behavior indicators may present. Consider

Use the B-SAHF model to help you frame your answers.

You have responded to a fire in a one-story single family dwelling of wood frame construction. A growth stage fire is burning a bedroom on the Alpha Bravo corner of the structure. The fire involves a plastic trash can, the bed, and night stand.

• What conditions would you expect to see from the exterior of the structure?
• What indicators may be visible from the front door as you make entry?
• What indicators would you anticipate observing as you traveled through the living room and down the hallway to the bedroom where the fire is located?
• What conditions would you find in the bedroom?

As the fire moves through the growth stage, the speed at which conditions change increases rapidly. After making entry, consider if conditions are different than you anticipated?

• Why might this be the case?
• What differences in conditions would be cause for concern?

More to Follow

The next post in this series will continue examination of the relationship between the B-SAHF indicators, fire development, and burning regime by connecting to the parallel series of posts on flashover and examining fully developed fires.

Ed Hartin, MS, EFO, MIFireE, CFO

References

National Institute of Standards and Technology. (2005). ISO-room/living room flashover [digital video disk]. Gaithersburg, MD: Author.

Building Factors, Smoke, Air Track, Heat, and Flame (B-SAHF) are critical fire behavior indicators. Understanding the indicators is important, but more important is the ability to integrate these factors in the process of reading the fire as part of size-up and dynamic risk assessment.

This post reviews application of the B-SAHF organizing scheme to recognizing and identifying stages of fire development and burning regime.

Compartment Fire Development

Part of the process of reading the fire involves recognizing the stages of fire development and burning regime (e.g., fuel or ventilation controlled). Remember that fire conditions can vary considerably throughout the building with one compartment containing a fully developed fire, an adjacent compartment in the growth stage, and still other compartments yet uninvolved. Similarly, burning regime may vary from compartment to compartment. Recognizing the stages of fire development and burning regime allows firefighters to predict what is likely to happen next (if action is not taken), potential changes due to unplanned ventilation (such as failure of a window), and the likely effect of tactical action.

Compartment fire development can be described as being comprised of four stages: incipient, growth, fully developed and decay (see Figure 1). Flashover is not a stage of development, but simply a rapid transition between the growth and fully developed stages.

Figure 1. Heat Release Rate (HRR) and Fire Development

Compartment fires do not always follow the simple, idealized fire development curve illustrated in Figure 1. The speed with which the fire develops, peak heat release rate, and duration of burning are dependent on both the characteristics of the fuel involved and ventilation profile (available oxygen).

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 fire’s 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, potentially resulting in a ventilation induced flashover as illustrated in Figure 2.

Figure 2. Ventilation Induced Flashover

Incipient Stage

Going back to the basics of fire behavior, ignition requires heat, fuel, and oxygen. Once combustion begins, development of an incipient fire is largely dependent on the characteristics and configuration of the fuel involved (fuel controlled fire). Air in the compartment provides adequate oxygen to continue fire development. During this initial phase of fire development, radiant heat warms adjacent fuel and continues the process of pyrolysis. A plume of hot gases and flame rises from the fire and mixes with the cooler air within the room. This transfer of energy begins to increase the overall temperature in the room. As this plume reaches the ceiling, hot gases begin to spread horizontally across the ceiling. Transition beyond the incipient stage is difficult to define in precise terms. However, as flames near the ceiling, the layer of hot gases becomes more clearly defined and increase in volume, the fire has moved beyond its incipient phase and (given adequate oxygen) will continue to grow more quickly.

Depending on the size of the compartment and ventilation profile, there may only be a limited indication (or no indication at all) from the exterior of the building that an incipient stage fire is burning within. Incipient stage indicators are listed in Figure 3

Figure 3. B-SAHF Indicators of an Incipient Stage Fire

Application Exercise

Consider the following situation and how critical fire behavior indicators would present. Use the B-SAHF model to help you frame your answers.

You have responded to a fire in a one-story single family dwelling of wood frame construction. An incipient fire is burning in a bedroom on the Alpha Bravo corner of the structure. The fire is limited to a plastic trash can containing waste paper which is located next to the bed.

• What conditions would you expect to see from the exterior of the structure?
• What indicators may be visible from the front door as you make entry?
• What might you observe traveling through the living room and down the hallway?
• What conditions would you find in the bedroom?

It is essential to think about what you are likely to find inside when observing fire behavior indicators from the exterior and performing a risk assessment. After making entry, consider if conditions are different than you anticipated.

• Why might this be the case?
• What differences in conditions would be cause for concern?

More to Follow

The next post in this series will continue examination of the relationship between the B-SAHF indicators, fire development, and burning regime with a look at growth stage fires in both fuel and ventilation controlled burning regimes.

Ed Hartin, MS, EFO, MIFireE, CFO

This post continues study of an incident in a townhouse style apartment building in Washington, DC with examination of the extreme fire behavior that took the lives of Firefighters Anthony Phillips and Louis Mathews.

A Quick Review

Prior posts in this series, Fire Behavior Case Study of a Townhouse Fire: Washington, DC and Townhouse Fire: Washington, DC-What Happened examined the building and initial tactical operations at this incident. The fire occurred in the basement of a two-story, middle of building, townhouse style apartment with a daylight basement. This configuration provided an at grade entrance to the Floor 1 on Side A and at grade entrance to the Basement on Side C.

Engine 26, the first arriving unit reported heavy smoke showing from Side A and observed a bi-directional air track at the open front door. First alarm companies operating on Side A deployed hoselines into the first floor to locate the fire. Engine 17, the second due engine, was stretching a hoseline to Side C, but had insufficient hose and needed to extend their line. Truck 4, the second due truck, operating from Side C opened a sliding glass door to the basement to conduct search and access the upper floors (prior to Engine 17’s line being in position). When the door on Side C was opened, Truck 4 observed a strong inward air track. As Engine 17 reached Side C (shortly after Rescue 1 and a member of Truck 4 entered the basement) and asked for their line to be charged, and Engine 17 advised Command that the fire was small.

Extreme Fire Behavior

Proceeding from their entry point on Side C towards the stairway to Floor 1 on Side A, Rescue 1B and the firefighter from Truck 4 observed fire burning in the middle of the basement room. Nearing the stairs, temperature increased significantly and they observed fire gases in the upper layer igniting. Rescue 1B and the firefighter from Truck 4 escaped through the basement doorway on Side C as the basement rapidly transitioned to a fully developed fire.

Figure 1. Timeline Leading Up to the Extreme Fire Behavior Event

The timeline illustrated in Figure 1 is abbreviated and focuses on a limited number of factors. A detailed timeline, inclusive of tactical operations, fire behavior indicators, and fire behavior is provided in a subsequent section of the case.

After Engine 17’s line was charged, the Engine 17 officer asked Command for permission to initiate fire attack from Side C. Command denied this request due to lack of contact with Engines 26 and 10 and concern regarding opposing hoselines. Due to their path of travel around Side B of the building, Engine 17 had not had a clear view of Side A and thought that they were at a doorway leading to Floor 1 (rather than the Basement). At this point, neither the companies on Side C nor Command recognized that the building had three levels on Side C and two levels on Side A.

At this point crews from Engine 26 and 10 are operating on Floor 1 and conditions begin to deteriorate. Firefighter Morgan (Engine 26) observed flames at the basement door in the living room (see Figure 8 which illustrates fire conditions in the basement as seen from Side C). Firefighter Phillips (Engine 10) knocked down visible flames at the doorway, but conditions continued to deteriorate. Temperature increased rapidly while visibility dropped to zero.

As conditions deteriorated, Engine 26’s officer feels his face burning and quickly exits (without notifying his crew). In his rapid exit through the hallway on Floor 1, he knocked the officer from Engine 10 over. Confused about what was happening Engine 10’s officer exited the building as well (also without notifying his crew). Engine 26’s officer reports to Command that Firefighter Mathews was missing, but did not report that Firefighter Morgan was also missing. Appearing dazed, Engine 10’s officer did not report that Firefighter Phillips was missing.

Figure 2. Conditions on Side C at Aproximately 00:28

Note: From Report from the Reconstruction Committee: Fire at 3146 Cherry Road NE, Washington DC, May 30, 1999, p. 32. District of Columbia Fire & EMS, 2000.

Figure 3. Conditions on Side A at Aproximately 00:28

Note: From Report from the Reconstruction Committee: Fire at 3146 Cherry Road NE, Washington DC, May 30, 1999, p. 29. District of Columbia Fire & EMS, 2000.

Firefighter Rescue Operations

After the exit of the officers from Engine 26 and Engine 10, the three firefighters (Mathews, Phillips, and Morgan) remained on Floor 1. However, neither Command (Battalion 1) nor a majority of the other personnel operating at the incident recognized that the firefighters from Engines 26 and 10 had been trapped by the rapid extension of fire from the Basement to Floor 1 (see Figure 4).

While at their apparatus getting a ladder to access the roof from Side B, Truck 4B observed the rapid fire development in the basement and pulled a 350′ 1-1/2″ (107 m 38 mm) line from Engine 12 to Side C, backing up Engine 17.

Figure 4. Location of Firefighters on Floor 1

Note: Adapted from Report from the Reconstruction Committee: Fire at 3146 Cherry Road NE, Washington DC, May 30, 1999, p. 18 & 20. District of Columbia Fire & EMS, 2000 and Simulation of the Dynamics of the Fire at 3146 Cherry Road NE, Washington D.C., May 30, 1999, p. 12-13, by Daniel Madrzykowski & Robert Vettori, 2000. Gaithersburg, MD: National Institute of Standards and Technology.

Engine 17 again contacted Command (Battalion 1) and requested permission to initiate an exterior attack from Side C. However, the officer of Engine 17 mistakenly advised Command that there was no basement entrance and that his crew was in position to attack the fire on Floor 1. Unable to contact Engines 10 and 26, Command denied this request due to concern for opposing hoselines. With conditions worsening, Command (Battalion 1) requested a Task Force Alarm at 00:29, adding another two engine companies, truck company, and battalion chief to the incident.

Firefighter Phillips (E-10) attempted to retreat from his untenable position at the open basement door. He was only able to travel a short distance before he collapsed. Firefighter Morgan (E-26) heard a loud scream to his left and then a thud as if someone had fallen to the floor (possibly Firefighter Mathews (E-26)). Firefighter Morgan found the attack line and opened the nozzle on a straight stream, penciling the ceiling twice before following the hoseline out of the building (to Side A). Firefighter Morgan exited the building at approximately 00:30.

Rescue 1B entered the structure on Floor 1, Side A to perform a primary search. They crawled down the hallway on Floor 1 towards Side C until they reached the living room and attempted to close the open basement door but were unable to do so. Rescue 1 B did not see or hear Firefighters Mathews (E-26) and Phillips (E-10) while working on Floor 1. Rescue 1B noted that the floor in the living room was spongy. The Rescue 1 Officer ordered his B Team to exit, but instead they returned to the front door and then attempted to search Floor 2, but were unable to because of extremely high temperature.

Unaware that Firefighter Phillips (E-10) was missing, Command tasked Engine 10  and Rescue 1A, with conducting a search for Firefighter Mathews (E-26). The Engine 10 officer entered Floor 1 to conduct the search (alone) while instructing another of his firefighters to remain at the door. Rescue 1A followed Engine 26’s 1-1/2″ (38 mm) hoseline to Floor 1 Slide C. Rescue 1B relocated to Side B to search the basement for the missing firefighter.

The Engine 26 Officer again advised Command (Battalion 1) that Firefighter Mathews was missing. Engine 17 made a final request to attack the fire from Side C. Given that a firefighter was missing and believing that the fire had extended to Floor 1, Command instructed Engine 17 to attack the fire with a straight stream (to avoid pushing the fire onto crews working on Floor 1). At approximately 00:33, Battalion 2 reported (from Side C) that the fire was darkening down. Engine 14 arrived and staged on Bladensburg Road.

Command ordered a second alarm assignment at 00:34 hours. At 00:36, Command ordered Battalion 2 (on Side C) to have Engine 17 and Truck 4 search for Firefighter Mathews in the Basement. Engine 10’s officer heard a shrill sound from a personal alert safety system (PASS) and quickly located Firefighter Phillips (E-10). Firefighter Phillips was unconscious, lying on the floor (see Figure 4) with his facepiece and hood removed. Unable to remove Firefighter Phillips by himself, the officer from Engine 10 unsuccessfully attempted to contact Command (Battalion 1) and then returned to Side A to request assistance.

Command received a priority traffic message at 00:37, possibly attempting to report the location of a missing firefighter. However, the message was unreadable.

The Hazmat Unit and Engine 6 arrived and staged on Bladensburg Road and a short time later were tasked by Command to assist with rescue of the downed firefighter on Floor 1. Firefighter Phillips (E-10) was removed from the building by the Engine 10 officer, Rescue 1A, Engine 6, and the Hazardous Materials Unit at 00:45. After Firefighter Phillips was removed to Side A, Command discovered that Firefighter Mathews (E-26) was still missing and ordered the incident safety officer to conduct an accountability check. Safety attempted to conduct a personnel accountability report (PAR) by radio, but none of the companies acknowledged his transmission.

The Deputy Chief of the Firefighting Division arrived at 00:43 and assumed Command, establishing a fixed command post at the Engine 26 apparatus. Battalion 4 arrived a short time later and was assigned to assist with rescue operations along with Engines 4 and 14.

Firefighter Mathews was located simultaneously by several firefighters. He was unconscious leaning over a couch on Side C of the living room (see Figure 4). Firefighter Mathews breathing apparatus was operational, but he had not activated his (non-integrated) personal alert safety system (PASS). Firefighter Mathews was removed from the building by Engine 4, Engine 14, and Hazardous Materials Unit at 00:49.

Command (Deputy Chief) ordered Battalions 2 and 4 to conduct a face-to-face personnel accountability report on Sides A and C at 00:53.

Questions

1. Based on the information provided in the case to this point, answer the following questions:
2. National Institute for Occupational Safety and Health (NIOSH) Death in the Line of Duty Reports examining incidents involving extreme fire behavior often recommend close coordination of fire attack and ventilation.
3. Did the fire behavior in this incident match the prediction you made after reading the previous post (Towhouse Fire: Washington DC-What Happened)?
4. What type of extreme fire behavior occurred? Justify your answer?
5. What event or action initiated the extreme fire behavior? Why do you believe that this is the case?
6. How did building design and construction impact on fire behavior and tactical operations during this incident?
7. How might a building pre-plan and/or 360^o reconnaissance have impacted the outcome of this incident? Note that 360^o reconnaissance does not necessarily mean one individual walking completely around the building, but requires communication and knowledge of conditions on all sides of the structure (e.g., two stories on Side A and three stories on Side C).
8. How might the outcome of this incident have changed if Engine 17 had been in position and attacked the fire in the basement prior to Engines 26 and 10 committing to Floor 1?
9. What strategies and tactics might have been used to mitigate the risk of extreme fire behavior during this incident?

More to Follow

This incident was one of the first instances where the National Institute of Standards and Technology (NIST) Fire Dynamics Simulator (FDS) was used in forensic fire scene reconstruction (Madrzykowski & Vettori, 2000). Modeling of the fire behavior in this incident helps illustrate what was likely to have happened in this incident. The next post in this series will examine and expand on the information provided by modeling of this incident.

Ed Hartin, MS, EFO, MIFireE, CFO

References

District of Columbia (DC) Fire & EMS. (2000). Report from the reconstruction committee: Fire at 3146 Cherry Road NE, Washington DC, May 30, 1999. Washington, DC: Author.

Madrzykowski, D. & Vettori, R. (2000). Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999, NISTR 6510. August 31, 2009 from http://fire.nist.gov/CDPUBS/NISTIR_6510/6510c.pdf

National Institute for Occupational Safety and Health (NIOSH). (1999). Death in the line of duty, Report 99-21. Retrieved August 31, 2009 from http://www.cdc.gov/niosh/fire/reports/face9921.html

The first post in this series, Reading the Fire: How to Improve Your Skills, I discussed building a concept map of fire behavior indicators as a method to increase competence in reading the fire. In the 12 posts that followed, we have explored each of the categories of the B-SHAF organizing scheme by developing a concept map for each type of indicator.

• How to Improve Your Skills
• Building Factors
• Building Factors Part 2
• Building Factors Part 3
• Smoke Indicators
• Smoke Indicators Part 2
• Air Track Indicators
• Air Track Indicators Part 2
• Heat Indicators
• Heat Indicators Part 2
• Heat Indicators Part 3
• Flame Indicators
• Flame Indicators Part 2

I have been working through this process as well in an effort to expand and refine my personal B-SAHF concept map. This post will review the work accomplished so far and lay the foundation for moving to the next step in the process; applying B-SAHF to recognize key indicators and predict likely fire behavior.

This review will be graphic, using the current version (5.2.2.1) of each of the concept maps developed in this series of posts.

Building Factors

Unlike the other elements of the B-SAHF organizing scheme for fire behavior indicators, Building Factors are present before the fire. Frank Brannigan was fond of saying “the building is the enemy” (Brannigan & Corbett, 2008, p. 81). The term enemy (2009) can be used to describe one who is antagonistic or seeking to injure or harm another. In this sense the building is not our enemy as it has no intent. However, it may also be used to describe something that is potentially harmful (Enemy, 2009). From this perspective Frank could be correct. However, I find that in the use of warfare as a metaphor for firefighting, I find it more useful to consider the building as the terrain that we fight on, rather than the enemy.

Building factors (such as use of lightweight or engineered wood support systems) present a significant hazard, but only under fire conditions. Fire dynamics and building performance under fire conditions are interrelated and should be key considerations in the pre-planning process.

In many respects, Building Factors is the most complex category of the fire behavior indicators. Figure 1 illustrates my current concept map capturing many (but likely not all) of the key building factors that influence fire behavior.

Figure 1. Building Factors

Consider what other building factors might be of interest or concern as well as how these factors may be interrelated with the other elements of the B-SAHF scheme.

Smoke Indicators

There are a significant number of interrelationships between smoke indicators and the other elements of the B-SAHF model, particularly Building Factors, Air Track, and Heat. These relationships reinforce the importance of looking at fire behavior indicators holistically, rather than simply as individual elements.

Figure 2. Smoke Indicators

Are there other indicators related to smoke that may be useful in identifying or assessing the stage of fire development, burning regime, or other important aspects of fire behavior? What additional interrelationships exist with the other elements of B-SAHF?

Air Track Indicators

Air track is the movement of both smoke (generally out from the fire area) and air (generally in towards the fire area). Air track is caused by pressure differentials inside and outside the compartment and by gravity current (differences in density between the hot smoke and cooler air). Air track indicators include velocity, turbulence, direction, and movement of the hot gas layer. As in the case of smoke, air track is closely interrelated with Building Factors, Smoke, and Heat Indicators.

Figure 3. Air Track Indicators

Are there other air track indicators that might be useful in assessing conditions and making predictions about likely fire behavior? What other interrelationships exist between air track and the other elements of B-SAHF?

Heat Indicators

In considering heat indicators, it is important to distinguish between energy, temperature, and heat. While this category is titled heat indicators, much of what we observe and feel is based on increased temperature due to transfer of energy (energy in transit is heat). To review the discussion of energy, temperature and heat, see Reading the Fire: Heat Indicators.

Figure 4. Heat Indicators

What other heat indicators may be useful in assessing conditions, the risk to firefighters, and impact of tactical operations on fire behavior? Are there additional interrelationships with other elements of B-SAHF?

Flame Indicators

Flames are the visible, light emitting product of combustion. In compartment fires, flames are the result of glowing particulate material (predominantly carbon). While extremely useful, information from flame indicators must be considered in conjunction with the other elements of B-SAHF.

Figure 5. Flame Indicators

Are there other flame related indicators that might be useful? Are there additional interrelationships with other elements of B-SAHF?

Applying B-SAHF

Developing your skill in reading the fire requires ongoing deliberate practice. What does this look like? In the following video clip, Tiger Woods is described as “just a pro who wants his game to get better, every day”

Are we professionals who want our skill at reading the fire to get better, every day? What does will it take for us to accomplish this task? It takes more than just talking about it or attending a class. Developing this level of skill requires ongoing, deliberate practice. Building a concept map of the B-SAHF indicators is an early step in this process as it gives you a way to think about information provided by the building and fire that will allow you to recognize important conditions and what is likely to happen next. Developing this understanding is necessary, but not sufficient. You also need to work on your skill at recognition and developing the ability to interpret this information in the context of the situation.

Using video is a great way to practice your skill in recognizing key indicators. On the fireground, you may only see a particular indicator for a few seconds. There is no instant replay. However, with video you can watch a particular clip again and again to practice your skill and develop the ability to separate critical indicators from the noise of extraneous information.

Practice Your Craft!

Reading the fire and recognizing likely and potential fire development is a critical part of initial size-up and action planning. However, this process needs to continue throughout incident operations as you evaluate the impact of tactical operations (the responsibility of everyone on the fireground, not just officers or the incident commander). Use the following two video clips of tactical operations to practice your skill (and maybe discover a few additional indicators to add to your B-SAHF concept maps).

Video Clip1-Roof Operations: Watch this video clip of vertical ventilation operations and identify the key B-SAHF Indicators. What information do the building, smoke, air track, heat, and flame indicators provide about current conditions? How is fire behavior likely to change?

Video Clip 2-Fire Attack: Watch this video clip of initial attack operations at a commercial fire. What building, smoke, air track, heat, and flame indicators can you observe in this clip? What information do these indicators provide? How do the indicators change based on application of water? What can you determine based these changes?

More to Follow

The next post in this series will begin to examine application of the B-SAHF scheme to recognizing stages of fire development and burning regime as part of initial and ongoing size-up and situation assessment.

Ed Hartin, MS, EFO, MIFireE, CFO

References

Brannigan, F. & Corbett, G. (2008). Building construction for the fire service. Sudbury, MA: Jones & Bartlett.

Enemy. (2009). In Merriam-Webster Online Dictionary. Retrieved September 17, 2009, from http://www.merriam-webster.com/dictionary/enemy

The previous post in this series, Reading the Fire: Flame Indicators briefly looked at flames, the visible, light-emitting product of combustion and identified several basic categories of flame related fire behavior indicators as illustrated in Figure 1.

Figure 1. Basic Flame Indicators

As with each of the B-SAHF (building, smoke, air track, heat, and flame) indicators, it is essential that assessment of flame related indicators is integrated with other elements of the B-SAHF scheme to gain a clearer sense of fire conditions and likely fire behavior.

Size and Location

Location of the flames may provide important information. If flames are visible from outside the structure, where are they coming from? It is important to connect this information with building factors such as compartmentation. Is fire showing from a single window due to compartmentation or simply because that is the only window that has failed? Are the flames pushing from inside a compartment or is smoke igniting and burning outside?

Given the conditions depicted in Figure 2, the size and location of flames make it obvious that the fire involves multiple compartments of this single family dwelling. However, it is important not to be distracted or deceived by conditions observed from one location!

Figure 2. Fire Showing from a Single Family Dwelling

Note: Photo by Marc Caron, Gatineau, Québec Canada

Early on the morning of July 21, 2007; Contra Costa County Engine 70 responded to a residential fire with persons reported at 149 Michelle Drive. On arrival, Engine 70 observed fire showing from the door and large picture window on Side A. From this limited view of the building, the fire appeared to be in the living room with potential for trapped occupants in the bedrooms. Engine 70 went to work knocking down the fire from the doorway and initiating a primary search of the bedrooms. However, conditions were not as simple as they seemed. The fire, which had originated in one of the bedrooms on Side B was burning in a ventilation controlled state with a substantial accumulation of gas phase fuel in the bedrooms and hallway. As Engine 70 conducted their search, increased ventilation returned the fire to flaming combustion, igniting the gas phase fuel (smoke) in a flash fire that killed Captain Matthew Burton and Engineer Scott Desmond (for more information on this incident see: Contra Costa LODD, Contra Costa LODD: Part 2, Contra Costa LODD: What Happened?).

It is absolutely critical that observation of flames be integrated with all of the B-SAHF indicators from more than one perspective. The first arriving officer should conduct a 360^o reconnaissance whenever possible. However, this is not always possible. If the first arriving company cannot accomplish this task, it does not diminish the importance of determining conditions on other sides of the building and another company should be assigned to complete this task as soon as possible.

While working inside the building, what is the flame height? Are the flames impinging on the ceiling and bending to travel horizontally? Do you observe flames in the hot gas layer (i.e., ghosting, rollover)? Fire development speeds considerably after flames in the plume of hot gases reach the ceiling and begin to travel horizontally in the ceiling jet. Isolated flames in the hot gas layer are a strong indicator of a ventilation controlled fire. Flames in the hot gas layer or development of rollover are an important indicator of imminent flashover.

With flame indicators, it is not just what you see that is important. What you do not see is equally important. Remember that the low oxygen concentration in backdraft conditions may preclude flaming combustion (at least in that compartment). However, conditions can vary widely from compartment to compartment (void spaces are compartments too!) and you may have visible flames from the exterior, but quite different conditions inside the building.

As with other fire behavior indicators, change over time is an important indication of fire development or progress towards control. This is particularly true with flaming combustion. Once fire control operations have started, firefighters and fire officers must evaluate the effect of fire streams. Failure of water application to reduce the size of the fire indicates that either the flow rate is inadequate, the application point is ineffective, or both.

Flame Color

Flame color is largely dependent on the type of fuel involved and the extent to which the fuel and oxygen are mixed (see the previous post Reading the Fire: Flame Indicators, Figure 2-Diffusion and Premixed Flames). Because there are several influences on flame color, it is important to interpret this information in context with other fire behavior indicators. Organic materials (natural or synthetic) will tend to burn with light yellow to reddish orange color depending on oxygen concentration as illustrated in Figure 3.

Figure 3. Fire Showing

Note: Photo courtesy of Mercer County Fire Protection District

While flame color can often be observed from the exterior as illustrated in Figure 3, it is also important while working inside as observed by Captain James Mendoza of the San Jose Fire Department.

The coloration of diffusion flames commonly encountered in structure fires runs from red to orange to yellow to almost white. This scale tells you something about the energy of the fire, with the redder the flame, the less temperature and radiant heat it is releasing. Often the lower energy red flames are due to combustion occurring with limited air, and if ventilation is increased, the energy released increases, temperature increases, and color changes from red to orange to yellow to white. So, if you are feeling extreme heat as you move towards dark orange flames, realize the air you just let in by opening the door can make the conditions worse, and you may be able to see that visually by a lighter flame color.

If organic fuel gas or vapor is premixed with air, flame color will be bluish. In compartment fires, a lazy bluish flame moving through the hot gas layer is an indication of a substantially ventilation controlled fire. However, it is important to remember that flame contact with other materials may influence color. For example, flame impinging on copper will have a blue green color.

Less commonly encountered in compartment fires, a bright white flame is usually indicative of high temperature such as that generated by burning metal (i.e., magnesium).

Duration

Given adequate fuel and oxygen, flaming combustion is likely to be continuous. However, when a compartment fire is burning in a ventilation controlled regime, flames may be intermittent as fuel and oxygen concentration varies. Watch the following video and observe the difference in flaming combustion from the window on Side B in the first 45 seconds (0:00 to 0:45) and from the window on Side A the next 30 seconds (00:46 to 1:16). How are the flames different? Why do you think that this is the case?

Work in Progress

Hopefully we have been working on this project together and you have been developing or refining the flame segment of your fire behavior indicators concept map. My current map is illustrated in Figure 4.

Figure 4. Flame Indicators Concept Map v5.2.2.1

You can also download a printer friendly version of the Flame Indicators Concept Map v5.2.2.1 As always, should you have any suggestions or feedback, please post a comment!

Ed Hartin, MS, EFO, MIFireE, CFO

This series of posts focused on Understanding Flashover has provided a definition of flashover; examined flashover in the context of fire development in both fuel and ventilation controlled fires; and looked at the importance of air track on rapid fire progression through multiple compartments. To review prior posts see:

• Myths and Misconceptions
• Myths and Misconceptions: Part 2
• The Ventilation Paradox
• The Importance of Air Track

This post begins study of an incident that resulted in two line-of-duty deaths as a result of extreme fire behavior in a townhouse style apartment building in Washington, DC. This case study provides an excellent learning opportunity as it was one of the first times that the National Institute of Standards and Technology (NIST) Fire Dynamics Simulator (FDS) and Smokeview were used in forensic fire scene reconstruction to investigate fire dynamics involved in a line-of-duty death. Data development of this case study was obtained from Death in the line of duty, Report 99-21 (NIOSH, 1999), Report from the reconstruction committee: Fire at 3146 Cherry Road NE, Washington DC, May 30, 1999 (District of Columbia (DC Fire & EMS, 2000), and Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999 (Madrzykowski & Vettori, 2000).

The Case

In 1999, two firefighters in Washington, DC died and two others were severely injured as a result of being trapped and injured by rapid fire progress. The fire occurred in the basement of a two-story, middle of building, townhouse apartment with a daylight basement (two stories on Side A, three stories on Side C).

Figure 1. Cross Section of 3146 Cherry Road NE

The first arriving crews entered Floor 1 from Side A to search for the location of the fire. Another crew approached from the rear and made entry to the basement through a patio door on Side C. Due to some confusion about the configuration of the building and Command’s belief that the crews were operating on the same level, the crew at the rear was directed not to attack the fire. During fireground operations, the fire in the basement intensified and rapidly extended to the first floor via the open, interior stairway.

Building Information

The unit involved in this incident was a middle of row 18′ x 33′ (5.6 m x 10.1 m) two-story townhouse with a daylight basement (see Figures 1 and 3). The building was of wood frame construction with brick veneer exterior and non-combustible masonry firewalls separating six individual dwelling units. Floors were supported by lightweight, parallel chord wood trusses. This type of engineered floor support system provides substantial strength, but has been demonstrated to fail quickly under fire conditions (NIOSH, 2005). In addition, the design of this type of engineered system results in a substantial interstitial void space between the ceiling and floor as illustrated in Figure 2.

Figure 2. Parallel Chord Truss Construction

Note: This is not an illustration of the floor assembly in the Cherry Road Townhouse. It is provided to illustrate the characteristics of wood, parallel chord truss construction.

The trusses ran from the walls on Sides A and C and were supported by steel beams and columns at the center of the unit (See Figure 3). The basement ceiling consisted of wood fiber ceiling tiles on wood furring strips which were attached to the bottom chord of the floor trusses. Basement walls were covered with gypsum board (sheetrock) and the floor was carpeted. A double glazed sliding glass door protected by metal security bars was located on Side C of the basement, providing access from the exterior. Side C of the structure (see Figure 3) was enclosed by a six-foot wood and masonry fence. The finished basement was used as a family room and was furnished with a mix of upholstered and wood furniture.

The first floor of the townhouse was divided into the living room, dining room, and kitchen. The basement was accessed from the interior via a stairway leading from the living room to the basement. The door to this stairway was open at the time of the fire (see Figures 1 and 3). The walls and ceilings on the first floor were covered with gypsum board (sheetrock) and the floor was carpeted. Contents of the first floor were typical of a residential living room and kitchen. A double glazed sliding glass door protected by metal security bars similar to that in the basement was located on Side C of the first floor. An entry door and double glazed kitchen window were located on Side A (see Figure 3). A stairway led to the second floor from the front entry. The second floor contained bedrooms (but was not substantively involved in this incident). There were double glazed windows on Sides A and C of Floor 2.

Figure 3. Plot and Floor Plan-3146 Cherry Road NE

Note: Adapted from Report from the Reconstruction Committee: Fire at 3146 Cherry Road NE, Washington DC, May 30, 1999, p. 18 & 20. District of Columbia Fire & EMS, 2000; Simulation of the Dynamics of the Fire at 3146 Cherry Road NE, Washington D.C., May 30, 1999, p. 12-13, by Daniel Madrzykowski & Robert Vettori, 2000. Gaithersburg, MD: National Institute of Standards and Technology, and NIOSH Death in the Line of Duty Report 99 F-21, 1999, p. 19.

Figure 4. Side A 3146 Cherry Road NE

Note: Adapted from Report from the Reconstruction Committee: Fire at 3146 Cherry Road NE, Washington DC, May 30, 1999, p. 17. District of Columbia Fire & EMS, 2000 and Simulation of the Dynamics of the Fire at 3146 Cherry Road NE, Washington D.C., May 30, 1999, p. 5, by Daniel Madrzykowski & Robert Vettori, 2000. Gaithersburg, MD: National Institute of Standards and Technology.

Figure5. Side C 3146 Cherry Road NE

Note: Adapted from Report from the Reconstruction Committee: Fire at 3146 Cherry Road NE, Washington DC, May 30, 1999, p. 19. District of Columbia Fire & EMS, 2000 and Simulation of the Dynamics of the Fire at 3146 Cherry Road NE, Washington D.C., May 30, 1999, p. 5, by Daniel Madrzykowski & Robert Vettori, 2000. Gaithersburg, MD: National Institute of Standards and Technology.

The Fire

The fire originated in an electrical junction box attached to a fluorescent light fixture in the basement ceiling (see Figures 1 and 3). The occupants of the unit were awakened by a smoke detector. The female occupant noticed smoke coming from the floor vents on Floor 2. She proceeded downstairs and opened the front door and then proceeded down the first floor hallway towards Side C, but encountered thick smoke and high temperature. The female and male occupants exited the structure, leaving the front door open, and made contact with the occupant of an adjacent unit who notified the DC Fire & EMS Department at 0017 hours.

Questions

It is important to remember that consideration of how a fire may develop and the relationship between fire behavior and your strategies and tactical operations must begin prior to the time of alarm. Assessment of building factors and fire behavior prediction should be integrated with pre-planning.

1. Based on the information provided about the fire and building conditions, how would you anticipate that this fire would develop?
2. What concerns would you have if you were the first arriving company at this incident?

More to Follow

My next post will examine dispatch information and initial tactical operations by first alarm companies.

Ed Hartin, MS, EFO, MIFireE, CFO

References

District of Columbia (DC) Fire & EMS. (2000). Report from the reconstruction committee: Fire at 3146 Cherry Road NE, Washington DC, May 30, 1999. Washington, DC: Author.

Madrzykowski, D. & Vettori, R. (2000). Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999, NISTR 6510. August 31, 2009 from http://fire.nist.gov/CDPUBS/NISTIR_6510/6510c.pdf

National Institute for Occupational Safety and Health (NIOSH). (1999). Death in the line of duty, Report 99-21. Retrieved August 31, 2009 from http://www.cdc.gov/niosh/fire/reports/face9921.html

National Institute for Occupational Safety and Health (NIOSH). (2005). NIOSH Alert: Preventing Injuries and Deaths of Fire Fighters Due to Truss System Failures. Retrieved August 31, 2009 from http://www.cdc.gov/niosh/fire/reports/face9921.html