Archive for September, 2009

Townhouse Fire: Washington, DC:
Computer Modeling

Monday, September 28th, 2009

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, Townhouse Fire: Washington, DC-What Happened,and Townhouse Fire: Washington, DC-Extreme Fire Behavior examined the building and initial tactical operations at this incident. The fire occurred in the basement of a two-story, middle of building, townhouse apartment with a daylight basement. This configuration provided at grade entrances to Floor 1 on Side A and 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. Engines 26 and 10 operating from 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. Engine 17 advised Command that the fire was small.

Conditions changed quickly after the door on Side C was opened, as conditions in the basement rapidly transitioned to a fully developed fire with hot gases and flames extending up the interior stairway trapping Firefighters Phillips, Mathews, and Morgan. Confusion about building configuration (particularly the number of floors and location of entry points on Side A and C) delayed fire attack due to concern for opposing hoselines.

Modeling of the Cherry Road Incident

National Institute for Standards and Technology (NIST) performed a computer model of fire dynamics in the fire at 3146 Cherry Road (Madrzykowski and Vettori, 2000) using the NIST Fire Dynamics Simulator (FDS) software. This is one of the first cases where FDS was used in forensic fire scene reconstruction.

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Fire modeling is a useful tool in research, engineering, fire investigation, and learning about fire dynamics. However, effective use of this tool and the information it provides requires understanding of its capabilities and limitations.

Models, such as the National Institute of Standards and Technology (NIST) Fire Dynamics Simulator (FDS) relay on computational fluid dynamics (CFD). CFD models define the fire environment by dividing it into small, rectangular cells. The model simultaneously solves mathematical equations for combustion, heat transfer, and mass transport within and between cells. When used with a graphical interface such as NIST Smokeview, output can be displayed in a three-dimensional (3D) visual format.

Models must be validated to determine how closely they match reality. In large part this requires comparison of model output to full scale fire tests under controlled conditions. When used for forensic fire scene reconstruction, it may not be feasible to recreate the fire to test the model. In these situations, model output is compared to physical evidence and interview data to determine how closely key aspects of model output matched events as they occurred. If model output reasonably matches events as they occurred, it is likely to be useful in understanding the fire dynamics involved in the incident.

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).

FDS output included data on heat release rate, temperature, oxygen concentration, and velocity of gas (smoke and air) movement within the townhouse. As indicated above, model output is an approximation of actual incident conditions.

In large scale fire tests (McGrattan, Hamins, & Stroup, 1998, as cited in Madrzykowski and Vettori, 2000), FDS temperature predictions were found to be within 15% of the measured temperatures and FDS heat release rates were predicted to within 20% of the measured values. For relatively simple fire driven flows such as buoyant plumes and flows through doorways, FDS predictions are within experimental uncertancies (McGrattan, Baum, & Rehm, 1998, as cited in Madrzykowski and Vettori, 2000).

Results presented in the NIST report on the fire at 3146 Cherry Road were presented as ranges to account for potential variation between model output and actual incident conditions.

Heat release rate is dependent on the characteristics and configuration of the fuel packages involved and available oxygen. In a compartment fire, available oxygen is dependent on the ventilation profile (i.e., size and location of compartment openings). The ventilation profile can change over time due to the effects of the fire (e.g., failure of window glazing) as well as human action (i.e., doors left open by exiting occupants, tactical ventilation, and tactical anti-ventilation)

In this incident there were a number of changes to the ventilation profile. Most significant of which were, 1) the occupant opened the second floor windows on Side C (see Figure 3), 2) the occupant left the front door open as they exited (see Figures 1 &2 ), 3) tactical ventilation of the first floor window on Side A, and opening of the sliding glass door in the basement on Side C (see Figures 1-3). In addition, the open door in the basement stairwell and open stairwell between the Floors 1 and 2 also influenced the ventilation profile (see Figure 1).

Figure 1. Cross Section of 3146 Cherry Road NE

cherry_road_cross_section

Figure 2. Side A 3146 Cherry Road NE

side_a_post_fire

Figure 3. Side C 3146 Cherry Road NE

side_c_post_fire

Figure 4 illustrates the timing of changes to the ventilation profile and resulting influence on heat release rate in modeling this incident. A small fire with a specific heat release rate (HRR) was used to start fire growth in the FDS simulation. In the actual incident it may have taken hours for the fire to develop flaming combustion and progression into the growth stage. Direct comparison between the simulation and incident conditions began at 100 seconds into the simulation which corresponds to approximately 00:25 during the incident.

Figure 4. FDS Heat Release Rate Curve

cherry_road_hrr_curve

Note: Adapted from Simulation of the Dynamics of the Fire at 3146 Cherry Road NE Washington D.C., May 30, 1999, NISTR 6510 (p. 14) by Dan Madrzykowski and Robert Vettori, 2000, Gaithersburg, MD: National Institute for Standards and Technology.

Questions

The following questions are based on heat release rate data from the FDS model presented in Figure 4.

  1. What was the relationship between changes in ventilation profile and heat release rate?
  2. What would explain the rapid increase in heat release rate after the right side of the basement sliding glass door is opened?
  3. Why might the heat release rate have dropped slightly prior to opening of the left side of the basement sliding glass door?
  4. Why did the heat release rate again increase rapidly to in excess of 10 MW after the left side of the basement sliding glass door was opened?
  5. How does data from the FDS model correlate to the narrative description of events presented in prior posts about this incident (Fire Behavior Case Study of a Townhouse Fire: Washington, DC, Townhouse Fire: Washington, DC-What Happened,and Townhouse Fire: Washington, DC-Extreme Fire Behavior)?

More to Follow

In addition to heat release rate data the computer modeling of this incident provided data on temperature, oxygen concentration, and gas velocity. Visual presentation of this data provides a more detailed look at potential conditions inside the townhouse during the fire. The next post in this series will present and examine graphic output from Smokeview to aid in understanding the fire dynamics and thermal environment encountered during this incident.

Master Your Craft

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

Incipient Stage Fires:
Key Fire Behavior Indicators

Thursday, September 24th, 2009

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

fire_development_curve_basic

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

vent_induced_flashover_curve

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

incipient_indicators

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?

Master Your Craft

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

Townhouse Fire: Washington, DC
Extreme Fire Behavior

Monday, September 21st, 2009

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

short_timeline_sr

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

fire_side_c_sr

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

fire_side_a_sr

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

location_of_ffs_sr

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 360o reconnaissance have impacted the outcome of this incident? Note that 360o 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.

Master Your Craft

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

Reading the Fire:
Putting it all Together

Thursday, September 17th, 2009

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.

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

building_factors_5-2-2-1

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

smoke_indicators_5-2-2-1

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

air_track_indicators_5-2-2-1

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

heat_indicators_5-2-2-1

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

flame_indicators_5-2-2-1

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.

Master Your Craft

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

Townhouse Fire: Washington, DC
What Happened

Monday, September 14th, 2009

This post continues 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.

A Quick Review

The previous post in this series, Fire Behavior Case Study of a Townhouse Fire: Washington, DC examined building construction and configuration that had a significant impact on the outcome of 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 an at grade entrance to the Basement on Side C.

The fire originated in an electrical junction box attached to a fluorescent light fixture in the basement ceiling (see Figures 1 and 2). 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.

Dispatch Information

At 00:17, DC Fire & EMS Communications Division dispatched a first alarm assignment consisting of Engines 26, 17, 10, 12, Trucks 15, 4, Rescue Squad 1, and Battalion 1 to 3150 Cherry Road NE. At 0019 Communications received a second call, reporting a fire in the basement of 3146 Cherry Road NE. Communications transmitted the update with the change of address and report of smoke coming from the basement. However, only one of the responding companies (Engine 26) acknowledged the updated information.

Weather Conditions

Temperature was approximately 66o F (19o C) with south to southwest winds at 5-10 mi/hr (8-16 km/h), mostly clear with no precipitation.

Conditions on Arrival

Approaching the incident, Engine 26 observed smoke blowing across Bladensburg Road. Engine 26 arrived at a hydrant at the corner of Banneker Drive and Cherry Road at 00:22 hours and reported smoke showing. A short time later, Engine 26 provided an updated size-up with heavy smoke showing from Side A of a two story row house. Based on this report, Battalion 1 ordered a working fire dispatch and a special call for the Hazmat Unit at 00:23. This added Engine 14, Battalion 2, Medic 17 and EMS Supervisor, Air Unit, Duty Safety Officer, and Hazmat Unit.

Firefighting Operations

DC Fire and EMS Department standard operating procedures (SOP) specify apparatus placement and company assignments based on dispatch (anticipated arrival) order. Note that dispatch order (i.e., first due, second due) may de different than order of arrival if companies are delayed by traffic or are out of quarters.

Standard Operating Procedures

Operations from Side A

The first due engine lays a supply line to Side A, and in the case of basement fires, the first line is positioned to protect companies performing primary search on upper floors by placing a line to cover the interior stairway to the basement. The first due engine is backed up by the third due engine. The apparatus operator of the third due engine takes over the hydrant and pumps supply line(s) laid by the first due engine, while the crew advances a backup line to support protection of interior exposures and fire attack from Side A.

The first due truck takes a position on Side A and is responsible for utility control and placement of ladders for access, egress, and rescue on Side A. If not needed for rescue, the aerial is raised to the roof to provide access for ventilation.

The rescue squad positions on Side A (unless otherwise ordered by Command) and is assigned to primary search using two teams of two. One team searches the fire floor, the other searches above the fire floor. The apparatus operator assists by performing forcible entry, exterior ventilation, monitoring search progress, and providing emergency medical care as necessary.

Operations from Side C

The second due engine lays a supply line to the rear of the building (Side C), and in the case of basement fires, is assigned to fire attack if exterior access to the basement is available and if it is determined that the first and third due engines are in a tenable position on Floor 1. The second due engine is responsible for checking conditions in the basement, control of utilities (on Side C), and notifying Command of conditions on Side C. Command must verify that the first and third due engines can maintain tenable positions before directing the second due engine to attack basement fires from the exterior access on Side C.

The second due truck takes a position on Side C and is responsible for placement of ladders for access, egress, and rescue on Side C. The aerial is raised to the roof to provide secondary access for ventilation (unless other tasks take priority).

Command and Control

The battalion chief positions to have an unobstructed view of the incident (if possible) and uses his vehicle as the command post. On greater alarms, the command post is moved to the field command unit.

Notes: This summary of DC Fire & EMS standard operating procedures for structure fires is based on information provided in the reconstruction report and reflects procedures in place at the time of the incident. DC Fire & EMS did not use alpha designations for the sides of a building at the time of this incident. However, this approach is used here (and throughout the case) to provide consistency in terminology.

First due, Engine 26 laid a 3″ (76 mm) supply line from a hydrant at the intersection of Banneker Drive and Cherry Road NE, positioned in the parking lot on Side A, and advanced a 200′ 1-1/2″ ( 61 m 38 mm) pre-connected hoseline to the first floor doorway of the fire unit on Side A (see Figures 1 and 2). A bi-directional air track was evident at the door on Floor 1, Side A , with thick (optically dense) black smoke from the upper area of the open doorway. Engine 26’s entry was delayed due to a breathing apparatus facepiece malfunction. The crew of Engine 26 (Firefighters Mathews and Morgan and the Engine 26 Officer) made at approximately 00:24.

Figure 1. Plot and Floor Plan-3146 Cherry Road NE

plot_and_floor

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.

Engine 10, the third due engine arrived shortly after Engine 26, took the hydrant at the intersection of Banneker Drive and Cherry Road, NE, and pumped Engine 26’s supply line. After Engine 10 arrived at the hydrant, the firefighter from Engine 26 who had remained at the hydrant proceeded to the fire unit and rejoined his crew. Engine 10, advanced a 400′ 1-1/2″ (122 m 38 mm) line from their own apparatus as a backup line. Firefighter Phillips and the Engine 10 officer entered through the door on Floor 1, Side A (see Figure 2) while the other member of their crew remained at the door to assist in advancing the line.

Truck 15, the first due truck arrived at 00:23 and positioned on Side A in the parking lot behind Engine 26. The crew of Truck 15 began laddering Floor 2, Side A, and removed kitchen window on Floor 1, Side A (see Figure 2). Due to security bars on the window, one member of Truck 15 entered the building and removed glass from the window from the interior. After establishing horizontal ventilation, Truck 15 accessed the roof via a portable ladder and began vertical ventilation operations.

Engine 17, the second due engine, arrived at 00:24, laid a 3″ (76 mm) supply line from the intersection of Banneker Drive and Cherry Road NE, to a position on Cherry Road NE just past the parking lot, and in accordance with department procedure, stretched a 350′ 1-1/2″ (107 m 38 mm) line to Side C (see Figure 2).

Approaching Cherry Road from Banneker Drive, Battalion 1 observed a small amount of fire showing in the basement and assigned Truck 4 to Side C. Battalion 1 parked on Cherry Road at the entrance to the parking lot, but was unable to see the building, and proceeded to Side A and assumed a mobile command position.

Second due, Truck 4 proceeded to Side C and observed what appeared to be a number of small fires in the basement at floor level (this was actually flaming pieces of ceiling tile which had dropped to the floor). The officer of Truck 4 did not provide a size-up report to Command regarding conditions on Side C. Truck 4, removed the security bars from the basement sliding glass door using a gasoline powered rotary saw and sledgehammer. After clearing the security grate Truck 4, broke the right side of the sliding glass door to ventilate and access the basement (at approximately 00:27) and then removed the left side of the sliding glass door. The basement door on Side C was opened prior to Engine 17 getting a hoseline in place and charged. After opening the sliding glass door in the basement, Truck 4 attempted to ventilate windows on Floor 2 Side C using the tip of a ladder. They did not hear the glass break and believing that they had been unsuccessful; they left the ladder in place at one of the second floor windows and continued with other tasks.

Figure 2. Location of First Alarm Companies and Hoselines

app_position

Note: Adapted from Report from the Reconstruction Committee: Fire at 3146 Cherry Road NE, Washington DC, May 30, 1999, p. 27. District of Columbia Fire & EMS, 2000.

Unknown to Truck 4, these windows had been left open by the exiting occupants. Truck 4B (two person team from Truck 4) returned to their apparatus for a ladder to access the roof from Side C. Rescue 1 arrived at 00:26 and reported to Side C after being advised by the male occupant that everyone was out of the involved unit (this information was not reported to Command). Rescue 1 and Truck 4 observed inward air track (smoke and air) at the exterior basement doorway on Side C and an increase in the size of the flames from burning material on the floor.

Engines 26 and 10 encountered thick smoke and moderate temperature as they advanced their charged 1-1/2″ (38 mm) hoselines from the door on Side A towards Side C in an attempt to locate the fire. As they extended their hoselines into the living room, the temperature was high, but tolerable and the floor felt solid. It is important to note that engineered, lightweight floor support systems such as parallel chord wood trusses do not provide reliable warning of impending failure (e.g., sponginess, sagging), failure is often sudden and catastrophic (NIOSH, 2005; UL, 2009).

Prior to reaching Side C of the involved unit, Engine 17 found that their 350′ 1-1/2″ (107 m 38 mm) hoseline was of insufficient length and needed to extend the line with additional hose.

Engine 12, the fourth arriving engine, picked up Engine 17’s line, completed the hoselay to a hydrant on Banneker Drive (see Figure 2). The crew of Engine 12 then advanced a 200′ 1-1/2″ (61 m 38 mm) hoseline from Engine 26 through the front door of the involved unit on Side A and held in position approximately 3′ (1 m) inside the doorway. This tactical action was contrary to department procedure, as the fourth due engine has a standing assignment to stretch a backup line to Side C.

Rescue 1’s B Team (Rescue 1B) and a firefighter from Truck 4 entered the basement without a hoseline in an effort to conduct primary search and access the upper floors via the interior stairway. Engine 17 reported that the fire was small and requested that Engine 17 apparatus charge their line.

Questions

Consider the following questions related to the interrelationship between strategies, tactics, and fire behavior:

  1. Based on the information provided to this point, what was the stage of fire development and burning regime in the basement when Engine 26 entered through the door on Floor 1, Side A? What leads you to this conclusion?
  2. What impact do you believe Truck 4’s actions to open the Basement door on Side C will have on the fire burning in the basement? Why?
  3. What is indicated by the strong inward flow of air after the Basement door on Side C is opened? How will this change in ventilation profile impact on air track within the structure?
  4. Did the companies at this incident operate consistently with DC Fire & EMS SOP? If not, how might this have influenced the effectiveness of operations?
  5. Committing companies with hoselines to the first floor when a fire is located in the basement may be able to protect crews conducting search (as outlined in the DC Fire & EMS SOP). However, what building factors increased the level of risk of this practice in this incident?

More to Follow

My next post will examine the extreme fire behavior phenomena that trapped Firefighters Phillips, Mathews, and Morgan and efforts to rescue them.

Master Your Craft

Remember the Past

This week marked the anniversary of the largest loss of life in a line-of-duty death incident in the history of the American fire service. Each September, we stop and remember the sacrifice made by those 343 firefighters. However, it is also important to remember and learn from events that take the lives of individual firefighters. In an effort to encourage us to remember the lessons of the past and continue our study of fire behavior, each month I include brief narratives and links to NIOSH Death in the Line of Duty reports and other documentation in my posts.

September 9, 2006
Acting CAPT Vincent R. Neglia
North Hudson Regional Fire & Rescue Department, NJ

Captain Neglia and other firefighters were dispatched to a report of fire in a three-story apartment building in Union City. Upon their arrival at the scene, firefighters found light smoke and no visible fire. Based on reports that the structure had not been evacuated, Captain Neglia and other firefighters entered the building to perform a search. Due to the light smoke conditions, Captain Neglia was not wearing his facepiece.

Captain Neglia was the first firefighter to enter an apartment. Conditions deteriorated rapidly as fire in the cockloft broke through a ceiling . Captain Neglia was trapped by rapid fire progress and subsequent collapse. Other firefighters came to his aid and removed him from the building. Captain Neglia was transported to the hospital but later died of a combination of smoke inhalation and burns.

NIOSH did not investigate and prepare a report on the incident that took the life of Captain Neglia.

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

Reading the Fire: Flame Indicators Part 2

Thursday, September 10th, 2009

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

flame_indicators_5-2-2

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

gatineau_fire

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 360o 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

flame_color_door

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

flame_indicators_5-2-2-1

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

Real Backdraft?

Wednesday, September 9th, 2009

I had intended to continue discussion of flame indicators in this post, but was motivated to address a common fire service myth based on information presented in an article in the New Canaan (Connecticut) Advertiser’s on-line newspaper titled Real ‘Backdraft’.

Figure 1. Backdraft Demonstration

revinge_backdraft_quad

Note: Photos of backdraft demonstration at the Swedish Civil Contingencies Agency College in Revinge, Sweden by Ed Hartin

The Question

The article was written by a fire officer in response to the question” “is there really such a thing as a backdraft as depicted in the 1991 Ron Howard movie by the same name?” His response to the question:

I found the movie very entertaining; however, I was completely distracted by the unrealistic depiction of fire and how it behaved compared to real life. . . . A backdraft occurs when a fire, in a confined space (room or building), has used up the available air and begins to starve for oxygen. When this occurs, great quantities of carbon monoxide (CO) are produced.

We all know that CO is the odorless, colorless and tasteless gas that can kill us. Another lesser known fact is that it is also highly flammable – like propane or natural gas.

This last characteristic is the catalyst for a backdraft. If a door or window is opened and a fresh supply of oxygen is introduced at the right (wrong) time, all of the built up CO will explode with devastating results.

Most action adventure films fail to depict fires and firefighting accurately, fueling (no pun intended) the public’s misperception of the hazards presented in the fire environment. While not likely the result of watching Backdraft and Ladder 49, many fire behavior myths and misperceptions persist in the fire service as well.

Fire Service Myth

The response to the question about backdraft is partially correct, this phenomenon involves introduction of air to a ventilation controlled fire. However, presumption that carbon monoxide is the predominant fuel in backdraft is a common fire service myth that is not supported by scientific research.

As observed by Gorbett and Hopkins (2007), there is considerable misunderstanding about extreme fire behavior such as flashover and backdraft. For example, many fire service texts and standards (e.g., National Fire Protection Association (NFPA) 402 Guide for Aircraft Rescue and Fire-Fighting Operations) continue to perpetuate the misconception that carbon monoxide concentration is a major determinant in the occurrence of backdraft.

Scientific Evidence

A substantial number of scientific studies have demonstrated that the major component of gas phase fuel involved in backdraft phenomenon is unburned, excess pyrolizate from solid fuel (Gottuk, 1999; Gojkovic, 2000; Sutherland, 1999; Fleischmann, 1993; Fleischmann & Pagni, 1993; and Weng & Fan, 2003). While backdraft conditions develop under ventilation controlled conditions with lower than normal (21%) oxygen concentration, the concentration of total hydrocarbons is the primary determinant of backdraft potential (Fleischmann, 1992 Weng & Fan, 2003).

As illustrated in Figure 2, smoke from incomplete combustion of organic materials includes a substantial concentration of unburned pyrolysis products. containing considerable potential (chemical) energy. If this gas phase fuel accumulates in sufficient concentration while the fire is in decay due to limited oxygen, an increase in ventilation may result in a backdraft.

Figure 2. Multi-Compartment Doll’s House Demonstration, Klana Croatia

smoke_is_fuel

Note: Photo by Nikola Tramontana, Vatrogasci Opatija, Croatia.

As actor and author Will Rogers said “It’s not what we don’t know that hurts, it’s what we know that ain’t so.” What I learned about fire behavior as a recruit firefighter was incomplete and in some cases inaccurate. I don’t fault the instructors or the textbook that was used as both were the best available at the time. However, it is important that we continue to push at the edges of our understanding of fire behavior and recognize that what we recognize as fact today may not be so tomorrow.

For more information on the backdraft phenomenon, see:

Barring another target of opportunity, my next post will return to Reading the Fire and revision and extension of the Flame Indicators concept map.

Ed Hartin, MS,EFO, MIFireE, CFO

References

Fleischmann, C. & Pagni, P. (1993) Exploratory backdraft experiments.” Fire Technology, 29(4), 298-316

Fleischmann, C. (1993) Backdraft phenomena, National Institute for Standards and Technology NIST-CGR-94-646). Retrieved March 26, 2009 from http://fire.nist.gov/bfrlpubs/fire94/PDF/f94008.pdf

Gojkovic, D. (2000) Initial backdraft experiments, Lund University. Sweden

Gorbett, G. & Hopkins, R. (2007). The Current Knowledge and Training Regarding Flashover, Backdraft, and Other Rapid Fire Progression Phenomenon. Retrieved March 19, 2009 from http://www.kennedy-fire.com/backdraft%20paper.pdfGottuk, D., Peatross, M., Farley, J. Williams, F. (1999) The development and mitigation of backdraft: A real-scale shipboard study. Fire Technology 33(4), 261-282.

Sutherland, B. (1999) Smoke sxplosions. University of Canterbury: Department of Engineering. Christchurch, New Zealand

Weng, W. & Fan, W. (2003). Critical condition of backdraft in compartment fires: A reduced scale experimental study. Journal of Loss Prevention in the Process Industries, 16, 19-26.

Fire Behavior Case Study
Townhouse Fire: Washington, DC

Monday, September 7th, 2009

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:

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

cherry_road_cross_section

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

paralell_chord_truss

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

plot_and_floor

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

side_a_post_fire

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

side_c_post_fire

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.

Master Your Craft

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

Reading the Fire: Flame Indicators

Thursday, September 3rd, 2009

In 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. Construction of a concept map increases awareness of key indicators and understanding their interrelationships. I am working through this process along with you, with the latest revision to my concept map. Thus far, I have examined Building Factors, Smoke Indicators, Air Track, and Heat Indicators the first fourcategories in the B-SAHF (Building, Smoke, Air Track, Heat, and Flame) organizing scheme. For review of the discussion of the work done so far, see the following Reading the Fire posts:

Focus Question

The process of developing or refining a concept map identifying fire behavior indicators (FBI) and their interrelationships starts with the following focus question:

What building, smoke, air track, heat, and flame indicators
provide clues to current and potential fire behavior?

As you develop the flame indicators concept map it is likely that you will uncover potential additions to the Building Factors, Smoke, Air Track or Heat Indicators concept maps. You may also identify interrelationships that you may not have thought of previously. Don’t forget to go back and capture these thoughts by adding them to your other maps or placing them in a staging area for further consideration.

Caution!

Flames get quite a bit of attention. Flames showing are sure to increase a firefighter’s pulse.

Figure 1. Flame Showing!

flame_showing

Note: Photo by Captain Jacob Brod, Pineville-Morrow Volunteer Fire Department

It is important to remember that while flames are an important fire behavior indicator, they provide only part of the picture. There is also a reason why they are last in the B-SAHF organizing scheme. Flame indicators must be integrated with Building, Smoke, Air Track, and Heat indicators to gain a more complete picture of incident conditions.

Flames

Flames are the visible, light emitting product of combustion. In compartment fires, flames are the result of glowing particulate material (predominantly carbon).

There are several distinctly different types of flames. Pre-mixed flames result when fuel vapor is mixed prior to combustion. The flame from a gas stove or heating appliance would be a good example of a pre-mixed flame. However, most of the flames encountered in a compartment fire are diffusion flames. In a diffusion flame, fuel defuses in the air to form a reaction zone containing fuel, air, and heat in the correct proportion to support combustion. Diffusion flames result from less efficient combustion (resulting in the presence of an increased percentage of unburned particulate material). The difference in appearance of pre-mixed and diffusion flames is illustrated in Figure 2.

Figure 2. Diffusion and Pre-Mixed Flames

bunsen_burner

Note: Each of these flames is being produced by the same fuel (Methane, CH4). The difference in appearance results from where the fuel and oxygen are mixed and the resulting efficiency of combustion.

Getting Started

Firefighters’ attention is often drawn to flames like a moth to a candle. However, this is only one of many fire behavior indicators. Visible flames may provide an indication of the size of the fire (i.e., fire showing from one window vs. fire showing from all windows on the floor). The size or extent of the fire may also be indicated by the effect (or lack of effect) of fire streams on flaming combustion.

As always in developing a concept map it is important to move from general concepts to those that are more specific. Flame Indicators can be divided into several categories as illustrated in Figure 3. However, you may choose to approach this somewhat differently.

Figure 3. Basic Flame Indicators

flame_indicators_5-2-2

Developing the Detail

Expanding the map requires identification of additional detail for each of the fundamental concepts. If an idea appears to be obviously related to one of the concepts already on the map, go ahead and add it. If you are unsure of where it might go, but it seems important, list it off to the side in a staging area for possible additions. Download a printer friendly version of Flame Indicators to use as a starting point for this process.

Next Steps

Remember that the process of contracting your own map is likely as important as the (never quite) finished product. The following steps may help you expand and refine the flame indicators segment of the map:

  • Look at each of the subcategories individually and brainstorm additional detail. This works best if you collaborate with others.
  • Have a look at the following video clip using your partially completed map and notes as a guide to identifying important flame indicators. While this video clip is of conditions on the exterior, also think about how this fire would present if viewed from the interior.

The next post in this series will discuss flame indicators in greater depth.

Ed Hartin, MS, EFO, MIFireE, CFO