Posts Tagged ‘deliberate practice’

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

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

Figure 1. Basic Flame Indicators

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

Size and Location

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

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

Figure 2. Fire Showing from a Single Family Dwelling

Note: Photo by Marc Caron, Gatineau, Québec Canada

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

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

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

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

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

Flame Color

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

Figure 3. Fire Showing

Note: Photo courtesy of Mercer County Fire Protection District

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

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

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

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

Duration

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

Work in Progress

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

Figure 4. Flame Indicators Concept Map v5.2.2.1

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

Ed Hartin, MS, EFO, MIFireE, CFO

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

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

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

The Case

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

Figure 1. Cross Section of 3146 Cherry Road NE

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

Building Information

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

Figure 2. Parallel Chord Truss Construction

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

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

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

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

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

Figure 4. Side A 3146 Cherry Road NE

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

Figure5. Side C 3146 Cherry Road NE

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

The Fire

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

Questions

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

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

More to Follow

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

Ed Hartin, MS, EFO, MIFireE, CFO

References

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

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

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

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

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

• Building Factors
• Building Factors Part 2
• Building Factors Part 3
• Smoke Indicators
• Smoke Indicators Part 2
• Air Track Indicators
• Air Track Indicators Part 2
• Heat Indicators
• Heat Indicators Part 2
• Heat Indicators Part 3

Focus Question

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

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

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

Caution!

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

Figure 1. Flame Showing!

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

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

Flames

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

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

Figure 2. Diffusion and Pre-Mixed Flames

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

Getting Started

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

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

Figure 3. Basic Flame Indicators

Developing the Detail

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

Next Steps

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

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

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

Ed Hartin, MS, EFO, MIFireE, CFO

Reading the Fire Heat Indicators briefly examined energy, temperature, and heat in thermodynamic systems, and introduced the two major categories of heat related fire behavior indicators: those that we can see (visual) and others that can be felt (tactile) as illustrated in Figure 1.

Figure 1. Basic Heat Indicator Categories

Heat Indicators Part 2 elaborated on tactile effects. This post will examine visual effects and provide an expanded heat indicators concept map.

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

Visual Effects

Air track often provides an early heat indicator. Observation of turbulent smoke pushing from the building at high velocity is a reliable indicator of a tremendous amount of heat energy and high temperatures inside the structure.

Figure 2. Air Track as a Heat Indicator

Note: Photo by Terry Moody, Ranlo NC.

Some visual indicators can be observed from the exterior such as bubbling paint, melting or softening roofing material, crazing glass, and condensation of pyrolyzate on windows. High temperature (and in some cases, not so high temperature) can have a more dramatic effect (see Figure 3). This vinyl frame window failed due to heat resulting from a fully developed fire inside the compartment.

Figure 3. Temperature Effects on Building Materials

Note: Photo by Ed Hartin

Fire stream effects such as evaporation of water from a hot surface (such as a door) or lack of return from a temperature check (brief application of water fog into the hot gas layer to check overhead temperature) also provide an indication of temperature (Figure 4)

Figure 4. Checking the Door and Temperature Check

Note: Photo by John McDonough

A thermal imaging camera (TIC) provides a highly effective means for visualizing temperature differences (see Figure 5). Use of a TIC should begin on the exterior and continue during interior operations.

Figure 5. Thermal Image

Note: Photo provided by Stefan Svensson

Despite the tremendous advantage provided by use of a TIC, it is essential to be mindful of the limitations of this technology. Thermal images only identify the temperature differences that are in direct line-of-sight. Insulating materials such as compartment linings can prevent the TIC from identifying fire conditions outside the compartment (e.g., floor below, ceiling void). In tests of floor and roof assemblies conducted by the Underwriters Laboratory (UL), thermal imaging cameras were unable to detect a fully developed fire below a typical wood floor (see Figure 6). The floor in Figure 6 consisted of an engineered system of I-joists, sub-floor, finished floor, carpet padding, and carpet. The floor system was being tested over a 14′ x 17′ (4.27 m x 5.18 m) gas fired furnace in accordance with ASTM E119. While the temperature indicated by the TIC is 80.1o F (27^o C), the highest temperature measured by thermocouples on the structural members was in excess of 1341o F (727^o C). It is essential to integrate thermal image data with direct visual observations to obtain a more complete picture of temperature conditions.

Figure 6. UL Floor Systems Test

Adapted from Underwriters Laboratory Structural Stability of Engineered Lumber in Fire Conditions [on-line training program]

The tests of engineered lumber systems and training program developed by UL provide excellent information on performance of these structural materials under fire conditions. This program as well as on-line training on fire behavior in single family dwellings and fire modeling are available free of charge from UL University.

Technological advancements also include temperature sensing integrated into breathing apparatus, personal alert safety systems (PASS), and even protective clothing (see Figure 7) to assist firefighters in recognizing dangerous elevated temperatures and in some cases telemetry to transmit this information to others, outside the hazardous environment. This could be viewed as a visual indicator (based on visual display of the information) or as augmentation of tactile indicators.

Figure 7. Smart Clothing by Viking Industries

Work in Progress

Hopefully we have been working on this project together and you have been developing or refining the air track segment of your fire behavior indicators concept map. My current map is illustrated in Figure 8.

Figure 8. Heat Indicators Concept Map v5.2.2.1

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

Ed Hartin, MS, EFO, MIFireE, CFO

References

Underwriters Laboratory. (2009). Structural Stability of Engineered Lumber in Fire Conditions [on-line training program]. Retrieved August 27, 2009 from http://www.ul.com/global/eng/pages/offerings/industries/buildingmaterials/fire/courses/structural/

As discussed in prior Reading the Fire posts and the ongoing series examining fire behavior indicators (FBI) using the B-SAHF (Building, Smoke, Air Track, Heat, and Flame) organizing scheme, developing proficiency requires practice. This post provides an opportunity to exercise your skills using three video segments shot during a commercial fire. In addition to practicing your skill in reading the fire, use these video clips to help develop or refine your smoke indicators concept map (see Reading the Fire: Smoke Indicators).

Commercial Fire

The Lake Station (IN) Fire Department was dispatched to a reported structure fire in the vicinity of the American Legion Hall on Central Avenue. Responding companies found a commercial building with fire and smoke showing at the intersection of Central Avenue and Howard Street.

Download and the B-SAHF Worksheet.

While the video clip of this incident does not allow you to walk around the building and observe fire conditions, Google maps street view allows you to view all sides of the building. If you haven’t used street view, have a look at the following Google Street View Tutorial.

Perform a “walkaround” by clicking on the following link to view the building involved at this incident: 1691 Central Ave, Lake Station, IN. Note: Radio communication in the video clip identifies the Incident Commander as “Howard Command”. However, for this activity, I have identified Central Avenue as the A Side of the involved building. Click on the arrows to move east on Central Avenue and move and adjust the compass rose to look at Side D. Move back along Central Avenue and then go down Howard Street, again adjusting the compass rose to look at Sides B and C. After your “walk around”, complete the Building Factors segment of the B-SAHF Worksheet.

The video clip of this incident begins with the view of Side B from the A/B Corner prior to the arrival of the first engine company. Watch the first 60 seconds of Video Segment 1. Consider the information provided in this segment of the video clip. First, describe what you observe in terms of the Building (add to what you have done so far), Smoke, Air Track, Heat, and Flame Indicators and then answer the following five standard questions:

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

Watch the next three minutes of the video and identify if, and how conditions change from the beginning of the clip until the first line is placed in operation (at approximately 04:00).

Watch the next 2 minutes 30 seconds until the firefighters make entry through the door on Side A (at approximately 06:30).

1. What conditions would you expect to find inside this part of the building?
2. How would you expect the fire to develop over the next two to three minutes?

Watch the remainder of the video clip.

Important: While not related to Reading the Fire, you likely heard the Personal Alert Safety System (PASS) device sounding through much of the incident. While PASS devices can (and often are) accidentally activated, continuous sounding of a PASS indicates a firefighter in distress. While this was not the case in this incident, failure to silence PASS devices that are accidentally activated desensitizes firefighters to this important audible signal.

Remember the Past

August 1994 saw the loss of two company officers and a firefighter in three separate incidents involving extreme fire behavior. Rapidly changing fire conditions are a threat to firefighters working in career staffed, urban fire departments and volunteer departments serving small communities.

August 7, 1994
Captain Wayne Smith
Fire Department of the City of New York, New York

On August 7, Captain Wayne Smith of the New York City Fire Department was critically injured while conducting search and rescue operations on an upper floor of a building when he was trapped by high heat and heavy smoke conditions. Captain Smith was burned over 40 percent of his body and received severe smoke inhalation injuries to his lungs. He died on October 4 from his injuries. Fourteen other firefighters were injured in the blaze. Initial operations were hampered by a faulty fire hydrant across the street from the building.

August 8, 1994
Sergeant Craig Drury
Highview Fire District, Kentucky

On August 8, Sergeant Craig Drury of the Highview (KY) Fire District was caught in a flashover while making entry into a single story house. Sgt. Drury suffered severe burns to his lungs that eventually caused his death. The fire was started by an arsonist.

August 27, 1994
Firefighter Paul MacMurray
Hudson Falls Volunteer Fire Department, New York

On August 27, Firefighter Paul MacMurray of the Hudson Falls (NY) Volunteer Fire Department responded as part of an engine company to a fire on the first floor of in a three story hotel. Assigned to search for and rescue occupants on the second floor, MacMurray and another firefighter successfully evacuated several victims while attempts to extinguish the fire were initiated below them. Upon their return to continue the search, conditions quickly changed from a light haze of smoke to black smoke with high heat conditions. MacMurray and his partner became separated in their attempt to locate the stairwell and get out of the building. The other firefighter made several efforts to locate MacMurray, but was forced to retreat due to untenable conditions. Several rescue efforts were made but heavy fire conditions eventually forced the evacuation of all fire personnel to defensive positions as the entire structure burned. MacMurray’s body was recovered the following day. The fire was of incendiary origin.

Ed Hartin, MS, EFO, MIFIreE, CFO

Reading the Fire Heat Indicators briefly examined energy, temperature, and heat in thermodynamic systems, and introduced the two major categories of heat related fire behavior indicators: those that we can see (visual) and others that can be felt (tactile) as illustrated in Figure 1.

Figure 1. Basic Heat Indicator Categories

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

The Thermal Environment

The thermal environment that firefighters encounter can be complex, but involves one or more of the following scenarios (Bryner, Madrzykowski, & Stroup, 2005):

• Immersion in a relatively static layer of hot gases (i.e., crawling or crouching in a room full of hot combustion products and smoke)
• Contact with a moving layer of hot gases (i.e., entry through a door or moving down a hallway with a strong air track)
• Exposure to radiant heat (i.e., working in proximity to flames or below a layer of hot gases)

Figure 2 illustrates the variations in temperature that firefighters may encounter during operations in a highly compartmentalized, multi-level structure. It is important to note that temperature varies from compartment to compartment and at different levels within each compartment.

Figure 2. Smokeview Slice

Note: Adapted from National Institute of Standards and Technology (NIST) Visualization techniques, Slice animation of a townhouse kitchen fire.

Firefighters’ personal protective equipment insulates them from the thermal environment. This layer of insulation makes it difficult to accurately assess temperature and heat flux (amount of heat transfer) that they are exposed to during firefighting operations. The thermal insulation provided by personal protective equipment slows, but does not stop heat transfer from the fire environment to the firefighter. Thermal exposure is dependent on gas temperature and radiant heat flux (heat transfer due to radiation)./

Thermal exposure can be divided into four categories: Ordinary, Hazardous, Extreme, and Critical (Foster & Roberts, 1995; Donnelly, Davis, Lawson, J., Selpak, 2006). As illustrated in Figure 3.

Figure 3. Thermal Exposure Limits in the Firefighting Environment

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

Several challenges confront firefighters in assessing the thermal environment during firefighting operations. These include:

• Of necessity, firefighters are insulated from their environment, delaying tactile perception of changes in temperature and heat flux.
• Perception of temperature is influenced by a wide range of factors and varies considerably from individual to individual.
• Firefighters focused on the task at hand may not notice subtle changes in temperature and heat flux.
• Temperature and heat flux do not always present obvious visual indicators.
• Conditions can change extremely rapidly, particularly as the fire approaches flashover.
• Firefighters may ignore warning signs of worsening conditions, believing that it is part of the job to tolerate extreme conditions.

Firefighters must have a sound understanding of the thermal environment encountered during firefighting operations and the, at times, subtle indicators of changing thermal conditions.

Tactile Effects

Tactile effects include sensing temperature or temperature change. Firefighters may sense temperature and changes in temperature, but as noted earlier, this is limited by the extent of thermal protection provided by their protective clothing and focus on the task at hand. Firefighters’ protective clothing effectively insulates them from the thermal hazards typically encountered in firefighting. The multiple layers of insulation in the protective ensemble slows (but does not stop) heat transfer. This time lag makes it difficult for the firefighter to appreciate their thermal exposure (Bryner, Madrzykowski, & Stroup, 2005).

Firefighter’s personal alert safety system (PASS) devices may be equipped with a temperature sensing function that provides warning at a specified exposure value when the specified temperature is exceeded for a specified time period (Figure 4). However, National Fire Protection Association 1982 Standard on Personal Alert Safety Systems (PASS) (NFPA, 2007) does not address thermal sensing and there is not standardized test protocol for these types of devices (Bryner, Madrzykowski, & Stroup, 2005). Thermal sensing devices use a temperature response curve to provide warning for long duration exposure to lower temperature and short duration exposure to higher temperature. However, during rapid increases in temperature such as those encountered in flashover or other forms of rapid fire development, adequate early warning to permit egress is unlikely due to limited sensitivity of the sensors (Bryner, Madrzykowski, & Stroup, 2005). While firefighters must be attentive to heat level and temperature change, it is often difficult to perceive these changes quickly enough to react to rapidly developing fire conditions. This reinforces the importance of integrating all the fire behavior indicators in your ongoing size-up and dynamic risk assessment.

Figure 4. PASS Device Temperature Sensor

Next Steps

The next post will conclude this look at Heat Indicators with examination of visual effects. While temperature and heat transfer cannot be observed directly, there are a number of ways in which firefighters can see the effects of temperature and heat.

Ed Hartin, MS, EFO, MIFireE, CFO

References

Bryner, N., Madrzykowski, D., Stroup, D. (2005). Performance of thermal exposure sensors in personal alert safety system (PASS) devices, NISTR 7294. Retrieved August 19, 2009 from http://www.fire.nist.gov/bfrlpubs/NIST_IR_7294.pdf.

Donnelly, M., Davis, W., Lawson, J., & Selpak, M. (2006). Thermal environment for electronic equipment used by first responders, NIST Technical Note 1474. Retrieved August 19, 2009 from http://www.fire.nist.gov/bfrlpubs/fire06/PDF/f06001.pdf

National Institute of Standards and Technology (NIST) Visualization techniques, Slice animation of a townhouse kitchen fire, [digital video file]. Retrieved August 19, 2009 from http://www.fire.nist.gov/fds4/refs/thouse3/thouse3_slice.avi

In Reading the Fire: How to Improve Your Skills, I discussed building a concept map of fire behavior indicators as a method to increase competence in reading the fire. Construction of a concept map increases awareness of key indicators and understanding their interrelationships. I am working through this process along with you, with the latest revision to my concept map. Thus far, I have examined Building Factors, Smoke Indicators, and Air Track Indicators, the first three categories in the B-SAHF (Building, Smoke, Air Track, Heat, and Flame) organizing scheme. For review of the discussion of the work done so far, see the following Reading the Fire posts:

• Building Factors
• Building Factors Part 2
• Building Factors Part 3
• Smoke Indicators
• Smoke Indicators Part 2
• Air Track Indicators
• Air Track Indicators Part 2

Focus Question

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

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

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

Heat and Temperature

Firefighters, like everyone else, have a commonsense understanding of heat and temperature. This is likely where many of our challenges in really understanding thermodynamics begins. The way in which we use the concepts of heat and temperature on a daily basis are likely to be considerably different than they are used in science.

Thermodynamics is a branch of physics that describes processes that involve changes in temperature, transformation of energy, and the relationships between heat and work. Fires and firefighting also involves changes in temperature, transformation of energy, heat and work. “Thermodynamics, like much of the rest of science, takes terms with an everyday meaning and sharpens them – some would say, hijacks them – so that they take on an exact an unambiguous meaning” (Atkins, 2007, p. 3).

Thermodynamics deals with systems. A thermodynamic system is one that interacts and exchanges energy with the area around it. A system could be as simple as a block of metal or as complex as a compartment fire. Outside the system are its surroundings. The system and its surroundings comprise the universe. For example we might consider a burning fuel package as the system and the compartment as the surroundings. On a larger scale we might consider the building containing the fire as the system and the exterior environment as the surroundings.

Figure 1. Thermodynamic Systems

In a compartment fire, energy is exchanged within the thermodynamic system and between the system and its surroundings.

Energy is the ability to do mechanical work or transfer thermal energy from one object to another. Energy can only be measured on the basis of its effects. There are basically two kinds of energy, kinetic and potential. Potential energy is that which is stored and may be released at a later time. The chemical energy contained in fuel that can be released during combustion is one example of potential energy. Kinetic energy is associated with motion of an object. Movement of molecules when heated during combustion is a good example of kinetic energy. Temperature is a measure of average kinetic energy.

The word flow is often used in discussing heat transfer (e.g., energy flows from materials with higher temperature to those with lower temperature). This helps visualize patterns of movement, but it is important to remember that neither energy nor heat is a fluid. Heat is the process of energy transfer due to temperature differences.

It is important to remember that we cannot see energy, temperature, or heat. However, we can see and feel the impact of increases in temperature as a result of heat (energy transfer). Use of the word heat to describe this category of indicators is appropriate as these indicators are all related to transfer of energy within and out of the compartment fires thermodynamic system.

Getting Started

When reading the fire it is important not to focus on a single indicator or category of indicators. In the case of heat, there are many interrelationships with air track and flame indicators. In some cases, it is arguable whether an indicator belongs in one category or the other (likely it is not important as long as you recognize the interrelationships).

As always in developing a concept map it is important to move from general concepts to those that are more specific. Heat Indicators can be divided into two basic categories, those that you can see (visual effects) and those that you can feel (tactile effects) as illustrated in Figure 2. However, you may choose to approach this somewhat differently.

Figure 2. Basic Heat Indicators

Developing the Detail

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

Next Steps

Remember that the process of contracting your own map is likely as important as the (never quite) finished product. The following steps may help you expand and refine the 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.
• Have a look at the following video clip using your partially completed map and notes as a guide to identifying important heat indicators. While this video clip is of conditions inside a compartment, also think about how this fire would present if viewed from the exterior.

The following video clip illustrates a recreation of the Station Night Club Fire that occurred in Rhode Island in 2003 that was conducted at the National Institute of Standards and Technology (NIST) laboratory in Gaithersburg, MD

The next post in this series will discuss visual and tactile heat indicators in greater depth and examine the increasing influence of technology in our perception (and misperception) of developing fire conditions.

Ed Hartin, MS, EFO, MIFireE, CFO

References

Atkins, P. (2000). Four laws that drive the universe. Oxford, UK: Oxford University Press

Just over a year ago I had the idea to develop a blog focused on compartment fire behavior and firefighting. A bit of work on the technology side and I made my introductory post on 8 August 2008. That month the CFBT-US web site had 2900 page views, this past July the page view count was in excess of 24,000 with 4400 unique readers. While this is not a huge readership in terms of the total number of firefighters in the world who have English as a language, it shows significant growth.

Accomplishments

At the start of this adventure, I set a goal to post twice weekly (Monday and Thursday mornings) and for the most part have managed to keep this schedule. Dominant themes have included:

• Reviews of books, training programs, magazine/journal articles, and conference presentations
• Case studies based on National Institute for Occupational Safety and Health (NIOSH) and agency reports on significant incidents, injuries, and fatalities
• An ongoing series of posts examining the B-SAHF (building, smoke, air track, heat, and flame) organizing scheme for fire behavior indicators and reading the fire
• B-SAHF video and photo based exercises in reading and interpreting B-SAHF indicators to predict likely fire behavior and the impact of tactical operations
• Examination of extreme fire behavior phenomena such as flashover, backdraft, smoke explosion, and flash fire with an emphasis on understanding the underlying causes and influence of tactical operations on fire dynamics
• Discussion of research on positive pressure ventilation and wind driven fires conducted by the National Institute for Standards and Technology
• Identification of the potential learning opportunity presented by systematic investigation of near miss, injury, and fatality incidents
• Discussion of the importance of deliberate practice and the concept of the need for 10,000 hours to master your craft

Hopefully you have found these posts useful in developing your understanding of compartment fire behavior or have motivated you to take action and share your knowledge of our profession with others. I have benefited greatly from the thought process and effort of writing on a regular and systematic basis.

As a reference, I have prepared a printer friendly Compartment Fire Behavior Blog Index in portable document format (PDF) which includes the date, title, URL, and brief synopsis of post content.

I Need Your Help

Your comments and feedback are important to making the Compartment Fire Behavior Blog better. If I write something that you do not agree with or think that a concept could be expressed more clearly, please comment or question!

The Way Forward

I am currently working on a loose editorial calendar to help guide my writing over the next year. Several important themes will continue:

• Case studies and lessons learned
• Reading the fire and B-SAHF exercises
• Practical fire dynamics
• Review of books, magazine/journal articles
• Fire control and tactical ventilation

If there are topics you think should be on the list, please provide your input as a comment on this post.

My next several posts will get back to study of the B-SAHF scheme with a look at Heat Indicators and continuing examination of flashover. As I have been looking back over the last year, I find that I have taken two distinctly different approaches to sequencing posts. Some topics have been addressed in successive posts (e.g., case studies and discussion of wind driven fires) and others have alternated between several different topics (e.g., B-SAHF and flashover). From my perspective, each has its advantages and disadvantages. If you have a preference or opinion, please let me know!

Thanks for your readership and participation,

Ed Hartin, MS, EFO, MIFireE, CFO

Air track includes factors related to the movement of smoke out of the compartment or building and the movement of air into the fire. Air track is caused by pressure differentials inside and outside the compartment and by gravity current (differences in density between the hot smoke and cooler air). Air track indicators include velocity, turbulence, direction, and movement of the hot gas layer.

My prior post, Reading the Fire: Air Track Indicators began the process of developing or refining an existing concept map of air track indicators. It is important to evaluate air track at openings and on the interior of the structure. As a starting point, I have identified direction, velocity & flow, and wind as basic air track indicator categories (see Figure 1). However, you may choose to approach this somewhat differently.

Figure 1. Basic Air Track Indicators

Air track indicators provide critical cues related to stages of fire development, burning regime, and potential for fire spread. However, it is essential that assessment of air track be integrated with other categories of indicators in the B-SAHF scheme to gain a clearer sense of fire conditions and likely fire behavior. Remember that looking at air track alone may be misleading.

Air Track at Openings and on the Interior

Discharge of smoke at openings and potential openings (Building Factors) is likely the most obvious indicator of air track while lack of smoke discharge may be a less obvious, but potentially important sign of inward movement of air.

Observation and interpretation of smoke and air movement at openings is an essential part of air track assessment, but it must not stop there. Movement of smoke and air on the interior can also provide important information regarding fire behavior.

The path taken by the air track will define the direction of fire spread and may present a significant hazard to firefighters operating between inlet and exhaust openings. This necessitates ongoing assessment of air track from both the exterior and interior of the building.

Figure 2. Air Track

Direction

Consider the following observations. You arrive at a fire in a commercial building and observe smoke showing from a door on floor 1 (Figure 2).

The smoke discharge fills the upper half of the door while it appears that air is moving in the bottom half of the door. What can you infer from this? What would you infer if the smoke discharge completely filled the door?

The direction of the air track can also provide valuable cues to fire behavior. When air moves in an opening (inlet) without any smoke discharge, it is likely that smoke is exiting from another opening (exhaust). When this condition is reversed, and smoke comes out with not inward movement of air, it is likely that another opening is serving as an inlet. When the air track is bi-directional and air moves in at the bottom and smoke moves out at the top, this may be the only opening in the compartment or ventilation from other exhaust openings may be inadequate. In any case where smoke is discharging through an opening, the fire is likely moving in that direction.

Mixing of smoke and air occurs at the interface between the hot gas layer and cooler air below. This is a critical factor in creating the conditions required for backdraft and many types of fire gas ignitions. Pulsing air track, outward movement of smoke followed by an inward movement of air is indicative of an underventlated fire and potential backdraft conditions (consider other indicators in determining if backdraft conditions are likely to exist). It is critical to remember that these pulsations can vary in duration and that backdraft does not generally occur immediately upon making an opening. The time between making an opening and occurrence of a backdraft is dependent on many factors including distance of the compartment with backdraft conditions from the opening. Air track is an extremely useful indicator, but it must be integrated with a big picture evaluation of fire behavior indicators.

Location of inlet and exhaust openings (particularly if they are on different levels or if impacted by wind) is an important Building Factor that directly impacts air track. This is an excellent example of why each of the categories of fire behavior indicators (FBI) must be considered together when reading the fire.

Velocity & Flow

Velocity and flow are two interrelated air track factors. Velocity refers to the speed of smoke and air movement. However, the speed with which smoke is traveling (either out of an opening in the compartment or building or within a compartment) must be considered in relation to the size of an opening or conduit. Flow may be either smooth (laminar) or turbulent. This is dependent to a large extent on velocity. High velocity generally results in turbulent flow through a compartment (such as a hallway) or out an opening (e.g., doorway or window). For a given volume, velocity and turbulence will be higher through smaller openings). High velocity smoke discharge and turbulent flow is generally indicative of high temperature within the compartment (another connection, in this case between air track and heat).

Wind

Wind can influence smoke movement on the exterior of a building (in some cases masking exterior air track indicators) or it can have a more direct influence on air track. As discussed in a number of earlier posts, wind can have a significant influence on compartment fire behavior.

• Wind Driven Fires
• NIST Wind Driven Fire Experiments: Establishing a Baseline
• NIST Wind Driven Fire Experiments: Anti-Ventilation Wind-Control Devices
• NIST Wind Driven Fire Experiments: Wind-Control Devices and Fire Suppression
• Wind Driven Fires: Tactical Problem

Understanding the potential influence of wind on fire behavior, provides a basis to read and interpret air track indicators. Wind exerts pressure on structural surfaces (see Figure 3), which under fire conditions can have a significant influence on movement of both smoke and air.

Figure 3. Distribution of Pressure due to Wind

Note. Adapted from Fire Ventilation (p. 34-35) by Stefan Svensson, 2000, Karlstad,Sweden: Räddnings Verket. Copyright 2000 by Stefan Svensson & Räddnings Verket.

Wind on an inlet opening can act much the same as a supercharger, dramatically increasing heat release rate, fire intensity, and rate of spread (see Figure 4).

Figure 4. Wind Effects

Movement of the Hot Gas Layer

Horizontal movement of the hot gas layer and turbulence at the interface between smoke and clear air below indicate air track direction. As discussed in Reading the Fire: Smoke Indicators height of the hot gas layer is a significant indicator of fire conditions. Even more important than the height of the hot gas layer, are changes in height. A sudden rise could indicate that ventilation has occurred (either performed by firefighters or caused by the fire). Gradual lowering of the hot gas layer could indicate worsening conditions and increased potential for flashover. However, inappropriate or excessive application of water can also cause lowering of the hot gas layer. Sudden lowering could indicate worsening conditions caused by flashover in an adjacent compartment. While not commonly known as a backdraft indicator, raising and lowing of the hot gas layer is similar to a pulsing air track observed at an opening (however in this case the compartment is not fully smoke logged, so the expanding and contracting gases cause the bottom of the hot gas layer to move up and down).

Height and more importantly vertical movement of the hot gas layer may be considered as Smoke or Air Track Indicators (a good argument can be made in either case). For now, I have chosen to position these two types of indicator under Smoke, but with linkage to Air Track, but I am considering moving them to Air Track (while maintaining linkage to Smoke Indicators).

Work in Progress

Hopefully we have been working on this project together and you have been developing or refining the air track segment of your fire behavior indicators concept map. My current map is illustrated in Figure 5.

Figure 5. Air Track Indicators Concept Map v5.2.2.1

You can also download a printer friendly version of the Air Track Indicators Concept Map v5.2.2.1 (including notes made during development). As indicated by the significant number of notes in the Staging Area of the printer friendly version, a bit more work remains to be done before integrating the Smoke and Air Track indicators in the complete version of the Fire Behavior Indicators Concept Map. Should you have any suggestions or feedback, please post a comment!

Ed Hartin, MS, EFO, MIFireE, CFO

References

Svensson, S. (2000). Fire ventilation. Karlstad, Sweden: Räddnings Verket.