Posts Tagged ‘burning regime’

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

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 66^o F (19^o 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

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

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.

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

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

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

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:

• Hazard of Ventilation Controlled Fires
• Smoke Explosion or Backdraft?
• Language & Understanding: Extreme Fire Behavior
• 15 Years Ago: Backdraft at 62 Watts Street
• 62 Watts Street: Modeling the Backdraft
• Extreme Fire Behavior: An Organizational Scheme (Ontology)
• Gas Explosions
• Gas Explosions Part 2

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.

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

This is the fourth in a series of posts dealing with flashover, to review prior posts see:

• Understanding Flashover: Myths and Misconceptions
• Understanding Flashover: Myths and Misconceptions: Part 2
• The Ventilation Paradox

As previously discussed flashover requires sufficient heat release rate for the temperature of fuel packages within a compartment to increase sufficiently to ignite and the fire to rapidly transition to the fully developed stage. However, during fire development in a compartment the fire often becomes ventilation controlled, with fire growth and heat release rate limited by the available air supply. In some cases, the fire generates sufficient heat release rate despite being ventilation controlled. In others, there is insufficient oxygen in the air supplied for the fire to reach flashover (unless ventilation is increased). All of this is fairly simple and straightforward if we are examining fire in a single compartment. This simple explanation of flashover is based on fire development in a single compartment, such as that described in the ISO 9705 Fire Tests-Full Scale Room Fire Tests for Surface Products6American Society for Testing and Materials (ASTM) Standard E 603-6 (Figure 1)

Figure 1. Full Scale (Six Sided) Room Fire Test Compartment

Note: Underwriters Laboratory (UL) fire test photo adapted from Fire Behavior in Single Family Dwellings, [PowerPoint Presentation], National Fire Academy.

Things get a bit more complex when a fire occurs in a multi-compartment building as individual compartments are interconnected smoke and flames may extend from compartment to compartment throughout the building.

Ventilation and Air Track

Contrary to the common fire service definition of ventilation as “[planned and] systematic removal of heated air, smoke, and fire gases and replacing them with cooler air (IFSTA, 2008), ventilation is simply the exchange of the atmosphere inside the building with that which is outside. This process is ongoing under normal, non-fire conditions. However, under fire conditions, ventilation also involves movement of smoke and air between compartments as well as discharge of smoke from the building and intake of air from outside the structure.

Remember! If you can see smoke coming from the building, ventilation is occurring (but not necessarily the type or amount of ventilation that you need to effectively control the fire environment and the fire).

The term air track is used to describe the characteristics of air and smoke movement (e.g., direction, velocity). The movement of both air and smoke are important, but the direction and path of smoke movement is particularly significant for several reasons:

• Smoke is fuel
• Hot smoke has energy

Through convection, smoke carries energy away from the fire compartment and transfers this energy to objects having lower temperature (such as other fuel packages or firefighters working inside the building). The rate of heat transfer is substantially dependent on temperature difference and in the case of convection on the velocity of the hot gases. Higher velocity and turbulence results in a higher rate of convective heat transfer (much the same as the increase in wind chill as wind speed increases in a cold environment).

Air Track on a Single Level

Examination of air track on a single level provides a simple way to illustrate the influence of air track on the movement of smoke (think fuel and energy) from compartment to compartment, fire extension, and multi-compartment flashover.

With no significant ventilation (with the exception of slight building leakage) smoke will fill the fire compartment and extend through openings such as doorways to adjacent compartments (see Figure 2). If insufficient oxygen is available from the air within the compartments the fire will become ventilation controlled and growth may slow and the fire may decay (heat release rate lessens)

Figure 2. Limited Ventilation

Note: Unless the building is tightly sealed, there is likely to be some leakage resulting in smoke discharge and inward movement of air.

If an opening is made in the presently uninvolved compartment, smoke will move from the fire to the opening, exiting out the upper area of the opening while cool air moves inward through the bottom of the opening and towards the fire (see Figure 3). This is a bi-directional air track.

Figure 3: Single Opening with Bi-Directional Air Track

As pointed out in The Myth of the Self-Vented Fire and The Ventilation Paradox, providing additional oxygen to a ventilation controlled fire results in increased heat release rate and may result in ventilation induced flashover. However, it is important to consider how this impacts adjacent compartments as well.

Increased heat release rate in a still ventilation controlled fire results in higher hot gas layer temperatures and increased smoke production. Increasing temperature and volume of the hot gas layer will cause it to lower and velocity to increase as the smoke moves through adjacent compartments and out ventilation openings. This increases both radiant and convective heat transfer and potentially speeds progression to flashover in adjacent compartments.

Horizontal tactical ventilation can be accomplished rapidly and may, under some conditions, be a useful approach to improving interior conditions. Increasing the number and size of horizontal openings can raise the level of the hot gas layer (by providing additional exhaust). However, when dealing with a ventilation controlled fire the increased oxygen supplied to the fire will increase heat release rate. In addition, in the absence of wind or application of positive pressure at the entry point, two openings at the same level will result in a bi-directional air track at both openings as illustrated in Figure 4.

Figure 4. Two Openings with a Bi-Directional Air Track

If heat release rate is sufficient, this may result in vent induced flashover in the compartments between the fire and the exhaust openings as illustrated in the following video clip.

Important! Horizontal ventilation is not a bad tactic. However, it is essential to recognize and manage the air track as well as ensuring that ventilation is coordinated with fire attack.

More to Follow

Examination of the flashover phenomenon will continue with a case study involving a 1999 fire in a Washington, DC townhouse that resulted in the line of duty deaths of two firefighters. This incident is particularly important as it is one of the first times that the National Institute of Standards and Technology (NIST) Fire Dynamics Simulator (FDS) and Smokeview were used for forensic fire scene reconstruction. This data, in conjunction with the District of Columbia Fire and EMS Reconstruction Report and National Institute for Occupational Safety and Health (NIOSH) Death in the Line of Duty Report provides a solid basis for understanding the impact of burning regime and air track in multi-compartment, ventilation induced flashover.

Ed Hartin, MS, EFO, MIFireE, CFO

References

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

A Quick Review

The first post in this series, Understanding Flashover: Myths & Misconceptions provided a definition of flashover and examined this extreme fire behavior phenomenon in the context of fire development in a compartment.

Flashover is the sudden transition to fully developed fire. This phenomenon involves a rapid transition to a state of total surface involvement of all combustible material within the compartment….Flashover may occur as the fire develops in a compartment or additional air is provided to a ventilation-controlled fire (that has insufficient fuel in the gas phase and/or temperature to backdraft).

Burning Regime

In the incipient and early growth stages of a compartment fire, the speed of fire growth is fuel controlled as fire development substantially influenced by the chemical and physical characteristics of the fuel. However, oxygen is required for the fuel to burn and release thermal energy. As a compartment fire develops, the available air supply for combustion becomes a more important factor. Increased combustion requires more oxygen and as smoke fills the compartment while the lowering neutral plane at compartment openings restricts the introduction of air into the compartment (see Figure 1).

The neutral plane is the level at a compartment opening where the difference in pressure exerted by expansion and buoyancy of hot smoke flowing out of the opening and the inward pressure of cooler, ambient temperature air flowing in through the opening is equal (Karlsson & Quintiere, 2000).

Figure 1. Lowering Neutral Plane

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

The distinction between fuel controlled and ventilation controlled is critical to understanding compartment fire behavior. Compartment fires are generally fuel controlled while in the incipient and early growth stage and again as the fire decays and the demand for oxygen is reduced (see Figure 2).

Figure 3. Fire Development with Limited Ventilation

While a fire is fuel controlled, the rate of heat release and speed of development is limited by fuel characteristics as air within the compartment and the existing ventilation profile provide sufficient oxygen for fire development. However, as the fire grows the demand for oxygen increases, and at some point (based on the vent profile) will exceed what is available. At this point the fire transitions to ventilation control. As illustrated in Figure 1, a ventilation controlled fire may reach flashover, all that is necessary is that sufficient oxygen be available for the fire to achieve a sufficient heat release rate for flashover to occur.

Heat Release and Oxygen

Combustion, as an oxidation reaction requires sufficient oxygen to react with the available fuel. Heat of combustion (energy released) and oxygen required for complete combustion are directly related (Thornton, 1917).The energy released per gram of oxygen consumed during complete combustion of natural and synthetic organic fuels is fairly consistent, averaging 13.1 kJ/g (±0.5%) (Huggett, 1980).

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

In the early 1900s, British scientist W.M. Thornton (1917) discovered that the amount of oxygen required per unit of energy released from many common hydrocarbons and hydrocarbon derivatives is fairly constant. In the 1970’s, researchers at the National Bureau of Standards independently discovered the same thing and extended this work to include many other types of organic materials and examined both complete and incomplete combustion (Huggett, 1980; Parker, 1977).

Each kilogram of oxygen used in the combustion of common organic materials results in release of 13.1 MJ of energy. This is referred to as Thornton’s Rule. See Fuel and Ventilation for a more detailed discussion of the application of Thornton’s Rule to compartment fires and ventilation.

Failure to Reach Flashover

Ventilation controlled compartment fires may reach flashover and fully developed compartment fires are generally ventilation controlled (IAAI, 2009). However, lack of ventilation may prevent a compartment fire from generating sufficient heat release rate to reach flashover. In some cases, ventilation controlled fires to not become fully developed, but decay and self-extinguish due to lack of oxygen.

In late 2007 an engine and truck company responded to a report of an odor of smoke in a three-story, wood-frame, apartment building. They discovered a ground floor apartment was smoke logged. They requested a first alarm assignment, forced entry, and initiated fire attack and primary search. Smoke was cool and to the floor, the fire was confined to an upholstered chair and miscellaneous items in the living room and at the time of entry was simply smoldering (see Figure 3). A rapid search discovered a deceased occupant in a bedroom remote from the fire.

Figure 3. Self-Extinguished Compartment Fire

Note: Gresham Fire & Emergency Services Photo

While a fire involving an upholstered chair typically results in sufficient heat release rate for the fire to extend to other nearby fuel packages and ultimately reach flashover, this fire did not as evidenced by the condition of the Christmas tree on the opposite side of the living room from the point of origin (see Figure 4). The Christmas tree, like many other fuel packages in the apartment showed evidence of pyrolysis, but did not ignite.

Figure 4. Condition of Other Fuel Packages

Note: Gresham Fire & Emergency Services Photo

Why didn’t this fire reach flashover? The fire occurred in early winter and the apartment’s energy efficient windows and doors were tightly closed. The developing fire consumed the oxygen available within the apartment and absent significant ventilation, decayed, and the temperature inside the apartment which had been increasing as the fire developed, dropped to a temperature slightly higher than would normally be expected inside an occupied apartment.

How might the development of this fire been different if it had been discovered earlier? What if a neighbor had opened a door or window in an effort to rescue the occupant? What if the fire department had opened the door without recognizing that the fire was significantly ventilation controlled?

When fire development is limited by the ventilation profile of the compartment, changes in ventilation will directly influence fire behavior. Reducing ventilation (i.e. by closing a door) will reduce the rate of heat release and slow fire development. Increasing ventilation (i.e. by opening a door or window) will increase the rate of heat release and speed fire development. Changes in ventilation profile may be fire caused (failure of glass in a window), occupants (leaving a door open), or tactical action by firefighters; but all will have an influence on fire behavior!

Figure 5. Ventilation Induced Flashover

For many years firefighters have been taught that ventilation reduces the potential for flashover. While this is sometimes true, it is only part of the story. Increasing ventilation to a fuel controlled fire will allow hot gases to exit, transferring thermal energy out of the compartment and replacing the hot gases with cooler air (which increases heat release rate). The combined influence of these two factors slows progression towards flashover and increases the heat release rate required to reach flashover. The bathtub analogy presented in Understanding Flashover: Myths and Misconceptions [LINK], does not apply in this case, because when a fire is ventilation controlled, heat release rate is limited by the available oxygen. Under ventilation controlled conditions; increasing air supply by creating opening results in increased heat release rate. This increased heat release rate may result in flashover (see Figure 5). For more information see Hazards of Ventilation Controlled Fires.

Two Paths to Flashover

With adequate fuel and oxygen, a growth stage compartment fire may flashover and rapidly transition to the fully developed stage. Given adequate fuel, but lacking adequate oxygen (due to limited ventilation), a growth stage compartment fire may begin to decay before becoming fully developed. However, this can quickly change if ventilation is increased, potentially resulting in ventilation induced flashover.

Understanding these two paths to flashover is essential, but still does not provide a complete picture of the flashover phenomena. The next post in this series will will use several case studies to examine the influence of air track on flashover in multiple compartments the threat that rapid fire progression presents to firefighters.

Ed Hartin, MS, EFO, MIFIreE, CFO

References

Karlsson, B. & Quintiere, J. (2000). Enclosure fire dynamics. New York: CRC Press.

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

Thornton, W. (1917). The relation of oxygen to the heat of combustion of organic compounds. The Philosophical Magazine,33(6), 196-203.

Parker, W. (1977). An investigation of the Fire Environment in the ASTM E 84 Tunnel Test, NBS Technical Note945. Gaithersburg, MD: U.S. Department of Commerce/National Bureau of Standards.

International Association of Arson Investigators (IAAI). (2009). Post flashover fires. On-Line Training Program, Downloaded August 6, 2009 from http://www.cfitrainer.net.

Fire Behavior Indicators – A Quick Review

The B-SAHF (Building, Smoke, Air Track, Heat, & Flame) organizing scheme for fire behavior indicators provides a sound method for assessment of current and potential fire behavior in compartment fires. The following provides a quick review of each of these indicator types.

Figure 1. B-SAHF

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

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

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

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

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

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

Getting Started

Considering the wide range of different building types and occupancies, developing a concept map of the factors and interrelationships that influence fire behavior is no simple task. As you begin this process, keep in mind that it is important to move from general concepts to more specific details. For example, you might select construction type, contents, size, ventilation profile, and fire protection systems as the fundamental factors as illustrated in Figure 2. (However, you also might choose to approach this differently!).

Figure 2. Basic Building Factors

Remember that this is simply a draft (as will each successive version of your map)! Don’t get hung up on getting it “right”. The key is to get started and give some thought to what might be important. After adding some detail, you may come back and reorganize the map, identifying another basic element. For example, early versions of this map listed Fire Suppression Systems (e.g., automatic sprinklers) as one of the core concepts. However, after adding some detail, this concept was broadened to Fire Protection Systems (e.g., automatic sprinklers, fire detection, and other types of inbuilt fire protection).

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. For example, area and height are important concepts related to size. However, compartmentation may be related to size or it may be a construction factor. If you are unsure of where this should appear on the map, place it in the Staging Area for now.

Figure 3. Expanding the Map

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 building factors segment of the map:

• Look at each of the subcategories individually and brainstorm additional detail. This works best if you collaborate with others.
• Take your partially completed map and notes and visit several different types of buildings. Visualize how a fire might develop and what building features would influence this process.
• Examine the incident profiled in the Remember the Past segment of this post and give some thought to how building factors may have influenced fire behavior and the outcome of this incident.

In addition, I am still posing questions related to B-SAHF using Twitter. Have a look [http://twitter.com/edhartin] and join in by responding to the questions. While this is not a familiar tool to most firefighters, I think that it has great potential.

Thanks

I would also like to thank Senior Instructor Jason Collits of the New South Wales (Australia) Fire Brigades and Lieutenant Matt Leech of Tualatin Valley Fire and Rescue (also an Instructor Trainer with CFBT-US, LLC) for their collaborative efforts on extending and refining our collective understanding of the B-SAHF indicators. Jason and Matt have been using Bubbl.us to develop and share their respective maps and I will be integrating their work into future posts on Fire Behavior Indicators.

Figure 4 Jason Collits and Matt Leech

Remember the Past

Yesterday was the eighth anniversary of a tragic fire in New York City that claimed the lives of three members of FDNY as a result of a backdraft in the basement of a hardware store.

June 17, 2001
Firefighter First Grade John J. Downing, Ladder 163
Firefighter First Grade Brian D. Fahey, Rescue 4
Firefighter First Grade Harry S. Ford, Rescue 3
Fire Department City of New York

Fire companies were dispatched to a report of a fire in a hardware store. The first- arriving engine company, which had been flagged down by civilians in the area prior to the dispatch, reported a working fire with smoke venting from a second-story window.

A bystander brought the company officer from the first-arriving engine company to the rear of the building where smoke was observed venting from around a steel basement door. The first-arriving command officer was also shown the door and ordered an engine company to stretch a line to the rear of the building. A ladder company was ordered to the rear to assist in opening the door; Firefighter Downing was a member of this company. The first-due rescue company, including Firefighters Fahey and Ford, searched the first floor of the hardware store and assisted with forcible entry on the exterior.

The incident commander directed firefighters at the rear of the building to open the rear door and attack the basement fire. Firefighters on the first floor were directed to keep the interior basement stairwell door closed and prevent the fire from extending. The rear basement door was reinforced, and a hydraulic rescue tool was employed to open it. Once the first door was opened, a steel gate was found inside, further delaying fire attack.

Firefighters Downing and Ford were attempting to open basement windows on the side of the building, and Firefighter Fahey was inside of the structure on the first floor.

An explosion occurred and caused major structural damage to the hardware store. Three fire-fighters were trapped under debris from a wall that collapsed on the side of the hardware store; several firefighters were trapped on the second floor; firefighters who were on the roof prior to the explosion were blown upwards with several firefighters riding debris to the street below; and fire-fighters on the street were knocked over by the force of the explosion.

The explosion trapped and killed Firefighters Downing and Ford under the collapsed wall; their deaths were immediate. Firefighter Fahey was blown into the basement of the structure. He called for help on his radio, but firefighters were unable to reach him in time.

The cause of death for Firefighters Downing and Ford was internal trauma, and the cause of death for Firefighter Fahey was listed as asphyxiation. Firefighter Fahey’s carboxyhemoglobin level was found to be 63%.

In addition to the three fatalities, 99 firefighters were injured at this incident. The fire was caused when children – two boys, ages 13 and 15 – knocked over a gasoline can at the rear of the hard-ware store. The gasoline flowed under the rear doorway and was eventually ignited by the pilot flame on a hot water heater.

For additional information on this incident, see the following:

NIOSH Death in the Line of Duty Report F2001-23,

Simulation of the Dynamics of a Fire in the Basement of a Hardware Store

Incident Photos by Steve Spak

Ed Hartin, MS, EFO, MIFireE, CFO

References

Grimwood, P., Hartin, E., McDonough, J., & Raffel, S. (2005). 3D firefighting: Training, techniques, & tactics. Stillwater, OK: Fire Protection Publications.

Hartin, E. (2007) Fire behavior indicators: Building expertise. Retrieved June 17, 2009 from www.firehouse.com.

Hartin, E. (2007) Reading the fire: Building factors. Retrieved June 17, 2009 from www.firehouse.com.

National Institute for Occupational Safety and Health (NIOSH). (2003) Death in the line of duty report F2001-23. Retrieved June 18, 2009 from http://www.cdc.gov/niosh/fire/pdfs/face200123.pdf

Bryner, N. & Kerber, S (2004) Simulation of the dynamics of a fire in the basement of a hardware store – New York, June 17, 2001 NISTR 7137. Retrieved June 18, 2009 from http://www.fire.nist.gov/bfrlpubs/fire06/PDF/f06006.pdf

United States Fire Administration (USFA) Firefighter fatalities in 2001. Retrieved June 18, 2009 from http://www.usfa.dhs.gov/downloads/pdf/publications/fa-237.pdf

As discussed in my last post, lack of an adequate exhaust opening is a common factor when use of positive pressure ventilation causes or increases the severity of extreme fire behavior. Unfortunately there has not been a great deal of research examining why this is the case. Part of the challenge in conducting a scientific investigation of this issue is the tremendous variability in building configuration and fire conditions. Control of these variables becomes more difficult as building configuration becomes more complex and multiple fire scenarios are considered. However, this does not preclude improvement of our understanding of this important issue.

Burning Regime

How an increase in ventilation influences fire behavior is largely (but not entirely) dependent on burning regime. If the fire is fuel controlled, fire development is dependent on the characteristics, configuration and amount of fuel. When a compartment fire becomes ventilation controlled, fire development is limited by the available oxygen. In the ventilation controlled burning regime, increased ventilation results in increased heat release rate. See my earlier post Fuel and Ventilation for additional information on burning regime.

In most ventilation controlled fires, the concentration of gas phase fuel (i.e., unburned pyrolyzate and flammable products of incomplete combustion) is not sufficient to present threat of backdraft. In these cases, increased ventilation will generally result in one of the following outcomes:

• Increase in heat release rate that is not sufficient to result in a rapid transition to a fully developed fire (flashover)
• Rapid increase in heat release rate that results in flashover and a fully developed fire.
• Intervention by firefighters to control the fire before ventilation induced flashover can occur.

If the concentration of gas phase fuel is sufficient to present threat of backdraft, increased ventilation may result in a backdraft…or not (depending on the extent of mixing of air and smoke, presence of an adequate ignition source, etc.).

The greater the extent to which the fire is ventilation controlled and the higher the concentration of gas phase fuel, the greater the potential for extreme fire behavior following increases in ventilation. Positive pressure ventilation influences this process in several ways, if effective, gas phase fuel is removed from the structure (often burning outside the exhaust opening). If PPV is not effective, increased air flow is accompanied with turbulence and resultant mixing of fuel an air which increases the probability of ignition and rapid fire progression. In addition, pressure applied at the outlet increases confinement which may increase the violence of extreme fire behavior phenomena such as backdraft.

Fluid Dynamics

Movement of fluids (liquids and gases) should be of significant interest to firefighters. Both fireground hydraulics and tactical ventilation require an understanding of fluid dynamics. In examining the influence of inadequate exhaust opening size on the effectiveness of PPV and potential for extreme fire behavior, I found some parallels with fireground hydraulics.

Laminar Flow: Smooth movement of a fluid in parallel layers with little disruption between the layers. The following video clip illustrates laminar flow in a pipe.

Turbulent Flow: Fluid flow characterized by eddies and vortexes disrupting smooth movement. The following video clip illustrates turbulent flow in a pipe.

A number of characteristics influence flow characteristics when a fluid moves through a conduit such as a pipe, hoseline, or even a building. These include fluid characteristics such as viscosity and density, the roughness of the conduit, restrictions to flow, and velocity of the fluid.

For example, friction loss in 1-1/2″ (38 mm) hose is higher than that in 1-3/4″ (45 mm) hose at the same flow rate. Why? Velocity must be higher to move the same flow rate through the smaller hose. This results in increased turbulence and resulting loss in pressure. If a discharge gate is partially closed, this obstructs the waterway, creating turbulence and increasing friction loss. As illustrated in this example, increased velocity and the presence of obstructions both increase turbulence. How does this apply to PPV?

The extent of turbulence as air and fire effluent (smoke and fire gases) move through a building is influenced by the configuration of the building (e.g., walls, doorways), obstructions (e.g., furniture), and velocity. Turbulence increases mixing of fire effluent and air. If the concentration of unburned pyrolizate and flammable products of incomplete combustion is high, turbulence increases the potential of a flammable mixture. In addition, increased oxygen concentration and air movement across surfaces can result in transition from surface to flaming combustion, providing a source of ignition for the flammable mixture of fire effluent and air.

Outlet/Inlet Ratio

When using natural ventilation, the size of the inlet opening(s) should be larger than the exhaust opening(s). However, with positive pressure ventilation this is reversed. When using PPV. exhaust opening(s) should be at least as large and preferably two to three times as large as the inlet opening as illustrated in Figure 1.

Figure 1. PPV Efficiency Curve

Note: Adapted from Fire Ventilation (Svensson, 2000, p. 71)

For a detailed examination of the physics and mathematical explanation of how the positive pressure ventilation efficiency curve is derived, see Stefan Svensson’s excellent text Fire Ventilation.

If the outlet size is adequate, a unidirectional ventilation flow from inlet to outlet is created. If opening size is inadequate, turbulence is increased as fire effluent and air seeks an exit path. If no opening is made or if the opening is extremely small, fire effluent may push back out the inlet opening.

Watch the following video clip and focus your attention on the exhaust opening on Side B (at approximately 0:19) and fire behavior indicators immediately after the blower is placed at the door on Side A and started (at approximately 3:00)

Find more videos like this on firevideo.net

Even though there was an exhaust opening, it was of inadequate size. While this fire was likely progressing towards a ventilation induced flashover due to the effects of natural horizontal ventilation, increased airflow and turbulence caused by ineffective PPV  likely was a contributing factor in the way that this extreme fire behavior phenomena occurred.

Important: Implementation of PPV after entry and before the fire has been located and controlled presents a significant risk to firefighters. Risk can be minimized by either using positive pressure attack (implementing PPV prior to entry) or locating and controlling the fire before implementing PPV.

Next Steps

In the Education vs. Training in Fire Space Control, Kris Garcia (2008) wrote that we need to increase our focus on ventilation education, rather than simply training on ventilation skills. Effective use of PPV to support fire attack or following fire control requires an understanding of fire and fluid dynamics as well as skill in creating openings and the placement and operation of blowers.

My next post will examine review Positive Thinking, an article by Watch Manager Gary West of the Lancashire Fire Rescue Service (UK) published in the August 2008 issue of Fire Risk Management. In this article, Gary provides an excellent overview of the approach to PPV training and implementation taken by the UK fire service.

References

Svensson, S. (2005). Fire ventilation. Karlstad, Sweden: Swedish Rescue Services Agency.

Garcia, K. (2008, September). Education vs. training in fire space sontrol. Fire Engineering. Retrieved May 21, 2009 from http://positivepressureattack.com/images/pdfs/EdVsTng-GarciaFESept08.pdf

West, G. (2008, August). Positive thinking. Fire Risk Management, 46-49.

This post continues examination of the incident that took the lives of Captain Matthew Burton and Engineer Scott Desmond early on the morning of July 21, 2007. Captain Burton and Engineer Desmond died while conducting primary search in a small, one-story, wood frame dwelling with an attached garage at 149 Michele Drive in San Pablo (Contra Costa County), California.

This post focuses on firefighting operations, key fire behavior indicators, and firefighter rescue operations implemented after Captain Burton and Engineer Desmond were discovered after rapid fire progression in the area in which they were searching.

Firefighting Operations

Based on the report of trapped occupants, E70 immediately placed a 150′ preconnected 1-3/4″ (45 m 45 mm) line into service using apparatus tank water. The officer of E70, seeing what he believed to be E74 arriving he passed command to the E74 officer. Unfortunately, the second arriving engine was E73 (using apparatus normally assigned to Station 74 and marked E74).

Note: This incomplete passing of command resulted in loss of command, control, and coordination of tactical operations until the arrival of BC7 at 0202 and formally assumed command at 0205. All tactical operations prior to 0205 were the result of independent action by first alarm companies.

The crew of E70 (officer and firefighter) initiated fire attack through the door on Side A and advanced 3′-5′ (0.9-1.5 m) through the door and quickly knocked down flaming combustion in the living room and through dispatch, requested the first arriving truck to establish vertical ventilation. Retrieving a thermal imaging camera (TIC) from the apparatus, the crew of E70 began a left hand search (towards the bedrooms), but left the hoseline just inside the door on Side A (see Figure 1)

Figure 1. Floor Plan-149 Michelle Drive

E73 hand stretched 200′ of 5″ (127 mm) supply line to a nearby hydrant. As he returned from the hydrant the firefighter from E73 observed a large volume of smoke from Side B. E73 officer tasked E70 engineer with placing a blower at the door on Side A. E73 (officer and firefighter) entered through the door on Side A and began a right hand search (taking the opposite direction from E70). E73 encountered poor visibility, but moderate temperature. While E73 conducted the search, E73 engineer shut off the natural gas service to the house.

E69 arrived at 0157 and prepared to perform vertical ventilation. The officer performed a size-up while the engineer obtained a chain saw and the firefighter placed a 14 ladder to provide access to the roof at the A/D corner. E70 engineer, asked the E69 officer about placing a blower to the front door (as previously ordered by the officer of E73) and he answered in the affirmative. The engineers from E70 and E73 placed a blower into operation 3′ (0.9 m) from the front door due to a half wall that partially enclosed the porch.

Note: No information is provided in the report regarding air track prior to or following pressurization of the building. The only substantive exhaust opening at the time the blower was placed into operation was the window in the living room immediately adjacent to the door on Side A.

E73 located the first civilian casualty, a female occupant in the kitchen (see Figures 2 and 5). As they removed the victim, both visibility and temperature increased dramatically. As they move the victim through the living room, they observed rollover coming from the hallway leading to the bedrooms (see Figures 2 and 5). The E73 officer briefly operated the hoseline left in the living room by E70 to control flaming combustion in the upper layer. The blower was turned 90^o to permit removal of the victim, but was then returned to its original operating position. E69 officer assigned the E69 firefighter to assist E73 with patient care on Side A.

The E69 officer and engineer proceeded to the roof and began making a vertical ventilation opening on Side A roof, over the hallway. At 0159 Q76 arrived and while the officer was donning his breathing apparatus (BA), the window in Bedroom 1 failed suddenly followed by a significant increase in flaming combustion from the windows in Bedroom 1 and 2 on Sides A and B.

The firefighter from E73 who was providing emergency medical care to the civilian fire victim observed that the window in Bedroom 1 which had been cracked with some discharge of smoke, failed violently with glass blowing out onto the lawn and a large volume of flames venting from the window for a period of 10 to 15 seconds (see Figure 2).

Figure 2. Extreme Fire Behavior

Note: Adapted from eight seconds of video was shot by Q76 firefighter from in front of Exposure D, looking towards the A/D corner of the fire building.

Figure 3. Post Fire Photo from in Front of Exposure D

Note: This screenshot from Google Maps Street View is from a similar angle as the video taken by Q76 firefighter and is provided to provide a point of reference and perspective for the video.

The E73 officer reentered the building and initiated fire attack using the hoseline left in the living room. E70 engineer stretched a second 150′ 1-3/4″ (45 m 45 mm) line to the front door. The second line was stretched into the building by Q76. Immediately after entering through the door on Side A, the Q76 met E73 officer who was exiting with low air alarm activation. Q76 took over the initial hoseline and worked their way down the hallway leading to the bedrooms, leaving the second line in the living room (see Figure 2) Q76 encountered poor visibility and high temperature with flames extending out of Bedrooms 1 and 2 and rollover in the hallway.

Shortly after exiting the building E73 officer advised E73 engineer that he was “out of air” [he was likely in a low air condition with low air alarm sounding rather than completely out of air] and expressed concern regarding E70’s air status.

Battalion 7 (BC7) arrived at 0202 and attempted to make face-to-face contact with Command (E70) as he had not heard E70 attempt to pass command to E74. At 0203, BC7 confirmed that a medic unit was responding and requested that the medic upgrade from Code 2 to Code 3. (Code 2 is a non-life threatening medical emergency requiring immediate response without the use of red lights or siren. Code 3 is a a medical emergency requiring immediate response with red lights and siren.) BC7 then attempted to contact E70 on the tactical channel and asked other crews operating at the incident about the status of E70. At 0205, BC7 ordered a second alarm and attempted to contact E70 on non-assigned tactical channels (in the event that their radios were inadvertently on the wrong channel). The second alarm added three engines (E74, E75, and E73) and a battalion chief (BC71) to the incident.

While BC7 was attempting to locate E70, Q76 was operating in the hallway and bedrooms in an effort to control the fire. They knocked the fire down in Bedroom 2 and controlled the rollover extending from Bedroom 1 down the hall. Q76 officer scanned Bedroom 2 with a TIC, but did not observe any victims. Q76 then advanced to Bedroom 1.

E69 completed a 6′ x 6′ (1.8 m x 1.8 m) ventilation opening in the roof on Side A, two thirds of the way from their access point at the A/D corner to Side B. Immediately after making the opening, they observed minimal smoke discharge (and were able to see items stored in the attic and the attic floor (original roof). They attempted to breach the attic floor, but were unable to do so (as it was constructed of 2″ x 6″ (51 mm x 152 mm) tongue and groove planks).

At 0206, after repeated unsuccessful attempts to contact E70, BC7 transmitted a report of a missing firefighter and assumed Command. Command requested an additional engine (E68) be added to the second alarm assignment. Battalion 64 (BC64) added himself to the incident and advised dispatch.

As E69 exited the roof they heard a loud pop and observed flames exiting the roof ventilation opening a distance of 8′-10′ (2.4-3.0 m). After knocking down the fire in Bedroom 1 Q76 moved back to Bedroom 2. Failure of the gypsum board on the wall between Bedrooms 1 and 2 allowed operation of the stream from their hoseline into both bedrooms.

While at the doorway of Bedroom 2, Q76 observed a substantial volume of fire in the attic through a small hole in the hallway ceiling (see Figure 4) and attempted to apply water into the attic. However, their stream was ineffective.

Figure 4. Hallway Ceiling.

Note: Adapted from Contra Costa Fire Protection District Photos, Investigation Report: Michele Drive Line of Duty Deaths. Brightness and contrast adjusted to increase clarity.

After exiting the roof, E69 proceeded counter clockwise around the building to Side C where they removed window screens and broke out several panes of glass, but did not observe an appreciable discharge of smoke. Continuing around the B/C corner, E69 observed flames from the window of Bedroom 2 and the attic.

At 0208 Command (BC7) repeatedly attempted to contact E70 by radio on the tactical channel. Unsuccessful, he requested an additional Code 3 ambulance and advised that the status of the missing firefighters was unknown.

E69 met with Command (BC7) and was assigned to continue primary search for the second reported occupant. E69 firefighter and engineer began the search while the officer replaced his SCBA cylinder. As they entered, they picked up a hoseline (second 1-3/4″ (45 mm) hoseline) and used it to extinguish small areas of fire as they moved towards the kitchen. Q76 handed off their TIC to E69 as they exited the building with low air alarms sounding.

Q76 replaced SCBA cylinders and was tasked with search for E70 on the exterior. While conducting this search, they observed flames 10′-15′ (3.0-4.6 m) in length issuing from the gable vent on Side B.

After E69 officer rejoined his crew in the kitchen, they located the second civilian casualty who was determined to be diseased (see Figure 2). Command (BC7) ordered E69 to defer removing the victim and continue searching for E70.

Firefighter Rescue Operations

E69 walked through the interior of the dwelling looking for E70 and used a hoseline to knock down fire still burning in the closet of Bedroom 2. E69 advised command that E70 was not inside, but was instructed to conduct a second search of the interior.

At 0127, Command (BC7) asked dispatch to conduct a “head count” [personnel accountability report (PAR)]. Second alarm resources arrived between 0218 and 0221.

E69 reentered the building and conducted a thorough search for E70. At 0221, Command (BC7) ordered companies to “evacuate” [withdraw from] the building. Based on the urgency of his assignment to locate E70, E69 officer decided to continue the search into Bedroom 2. At approximately 0222, E69 located Captain Burton (fire service casualty 1) under debris on the right side of the bed (see Figure 2). His facepiece was still in place and his low air alarm was ringing slowly. E69 attempted to remove the Captain, but were only able to move him to the doorway to Bedroom 2 before smoke conditions worsened and visibility decreased. Near exhaustion, one member of the crew experience low air alarm activation and became disoriented requiring assistance to exit to the door on Side A.

Command (BC7) assigned Q76 to assist with the search. As E69 exited, they advised Q76 that they had located one member of E70 in the bedroom. After exiting, E69 advised Command (BC7) that they had located one member of E70 and that he appeared to be diseased and that they were having difficulty in removing him. Q76 quickly located Captain Burton inside the doorway of Bedroom 2 and removed him to Side A at 0228. E73 attempted resuscitation, but quickly determined that the Captain’s injuries were fatal.

BC64 and E76 officer continued the search in Bedroom 2 and located Engineer Desmond (fire service casualty 2) on the left side of the bed (see Figure 2). E72 assisted in controlling the fire in Bedroom 2 and the removal of the second member of E70 on a backboard. Engineer Desmond was removed from the building at approximately 0224. After both members of E70 were removed, crews removed the deceased civilian occupant.

Timeline

Review the Michelle Drive Timeline (PDF format) to gain perspective of sequence and the relationship between tactical operations and fire behavior.

Questions

The following questions focus on fire behavior, influence of tactical operations, and related factors involved in this incident.

1. The E73 officer tasked E70 engineer with placement of a blower at the door on Side A (use of this tactic was reaffirmed by the E69 officer). What air track did this use of positive pressure create and what effect did this have on 1) conditions in the living room and kitchen and 2) in the hallway and bedrooms? Why do you think that this was the case?
2. What type of extreme fire behavior phenomena occurred in this incident? Do you agree with the Contra Costa County Fire Protection District report conclusion that this was a fire gas ignition or do you suspect that some other phenomenon was involved?
3. How did the conditions necessary for this extreme fire behavior event develop (address both the fuel and ventilation sides of the equation)?
4. What was the initiating event(s) that lead to the occurrence of the extreme fire behavior that trapped Captain Burton and Engineer Desmond? How did the use of positive pressure ventilation influence the occurrence of the extreme fire behavior (if in fact it did)?
5. What action could have been taken to reduce the potential for extreme fire behavior and maintain tenable conditions during primary search operations?
6. How did building design and construction impact on fire behavior and tactical operations during this incident?

Ed Hartin, MS, EFO, MIFireE, CFO

References

Contra Costa County Fire Protection District.  (2008). Investigation Report: Michele Drive Line of Duty Deaths. Retrieved February 13, 2009 from http://www.cccfpd.org/press/documents/MICHELE%20LODD%20REPORT%207.17.08.pdf

National Institute for Occupational Safety and Health (2009).  Death in the Line of Duty Report 2007-28. Retrieved May 5, 2009 from http://www.cdc.gov/niosh/fire/pdfs/face200728.pdf.