Posts Tagged ‘fire behavior indicators’

While I have not had much input (via Twitter or post comments), I have been working on the Building Factors map to include factors related to the surrounding environment and to revise fire protection systems, construction, fuel, size, and ventilation profile.

Surrounding Environment

Previous versions of the fire behavior indicators (FBI) concept map considered wind effects as a component of air track (which it influences significantly), but did not consider other environmental influences on fire behavior. After considerable thought, I recognized that building factors (and to some extent all of the FBI) can be viewed like Matryoshka Dolls (nested Russian dolls) when used to think about a single compartment, the building, or the building in its surrounding environment.

Environmental factors include exposures (which fire can extend from or to), ambient weather conditions, and terrain. Weather and terrain likely deserve a bit of explanation. While these factors are recognized as major players in wildland fire behavior, their influence is often not as quickly recognized in the built environment. Wind is likely the greatest meteorological concern when dealing with compartment fires. As discussed in prior posts (Wind Driven Fires, NIST Wind Driven Fire Experiments: Establishing a Baseline, Evaluating Firefighting Tactics Under Wind Driven Conditions), wind driven fires present a significant threat to firefighters. However, while buildings are generally designed to minimize the impact of temperature, humidity, and precipitation on their occupants, these factors can influence fire behavior directly or indirectly. For example, combustible exterior surfaces (e.g., wood shingle or shake roofs) present an increased hazard if humidity is low and ambient temperature is high. The influence of terrain may not be quite as obvious. In some cases, terrain may influence wind effects and in others slope may result in differences in elevation on each side of the building. When unrecognized, this has been a factor in a number of firefighter fatalities due to the resulting air track and path of fire spread from lower, to upper floors. For example see NIOSH (1999) Death in the Line of Duty Report F99-21 and Simulation of the Dynamics of the Fire at 3146 Cherry Road NE, Washington D.C. (NIST, 2000).

Fire Protection Systems

Fire suppression systems such as automatic sprinklers can obviously have a direct influence on fire development in a protected compartment. Similarly, fire detection may reduce the time between ignition and intervention by the fire department. However, prior versions of the FBI concept map did not include passive fire protection such as fire rated separations (other than generically as compartmentation).

Construction & Fuel

Prior versions of the FBI map linked Building to Contents and Construction. I have changed this to consider both contents and construction as fuel, while maintaining a link between building factors and construction as there are other facets of construction that can influence fire behavior. However, this area of the map remains a bit tentative (with more work to be done). Other changes to this part of the map include the addition of fire load density (kJ/m2) and increasing clarity of the concepts related to flow rate requirements for fire control.

Size

The concept of size can be a bit confusing as it applies to individual compartments (habitable or void spaces), interconnected compartments, and the entire building. Refinements include the addition of void spaces and normal door position to the concept of compartmentation.

Ventilation Profile

Thermal performance of potential openings has been added to ventilation profile, recognizing that single pane windows perform considerably different than multi-pane, energy efficient windows under fire conditions. In addition, a note was added to clarify that ventilation may be from compartment to compartment or from the building to the external environment.

Figure 1. Building Factors Concept Map v5.2.2.1

You can also download a larger, printer friendly version of the Building Factors Concept Map v5.2.2.1 (including notes made during development). Several colleagues who have had a look at this map observed that it is extremely complicated. While this is true, if you take the time to examine each of the factors and give some thought to the interrelated influences on fire behavior, it becomes a bit clearer. Remember that this is my representation of the concepts, yours will likely be a bit different! As always, feedback is greatly appreciated.

Subsequent posts will examine the rest of the B-SAHF (Building, Smoke, Air Track, Heat, & Flame) organizing scheme for fire behavior indicators.

Ed Hartin, MS, EFO, MIFireE, CFO

References

National Institute for Occupational Safety and Health (NIOSH) (1999) Death in the line of duty report F99-21. Retrieved July 2, 2009 from http://www.cdc.gov/niosh/fire/pdfs/face9921.pdf

National Insitute for Standards and Technology (NIST). Simulation of the Dynamics of the Fire at 3146 Cherry Road NE, Washington D.C. Retrieved July 2, 2009 from http://www.fire.nist.gov/CDPUBS/NISTIR_6510/6510c.pdf

In Reading the Fire: How to Improve Your Skills and Fire Behavior Indicators: Building Factors we started the process of developing a personal fire behavior indicators (FBI) concept map. I am working along with you to expand and refine my FBI Concept Map (Version 5.2.1).

Reading the Fire

I regularly post B-SAHF (Building, Smoke, Air Track, Heat, and Flame) Exercises to provide the opportunity to practice reading the fire. However, photos and video clips can also provide a great opportunity to focus in on a single type of indicator (such as building factors). Dig out the work in progress on your FBI concept map and have a look at the following video clips and focus your attention on building factors.

1. What type of construction was involved? How (or did) this factor influence fire behavior?
2. What other building and occupancy characteristics may have had an impact on fire behavior?
3. Are the factors you identified on your concept map? If not, add them to the map or list them in a staging area until you have determined where they might go on the map.

Los Angeles County Commercial Fire

Vancouver BC Apartment Fire

Los Angeles City Commercial Fire

What additions have you made to your FBI concept map? If you found this useful, poke around on YouTube and continue to apply this method to help you develop and refine the building factors (and other elements) of your map.

Step Back and Look at the Entire Picture

I would not want to waste the opportunity to engage with the rest of the B-SAHF indicators. Download and print three copies of the B-SAHF Worksheet. Consider the information provided in each of the short video clips and complete the worksheet for each. First, describe what you observe in terms of the Building, Smoke, Air Track, Heat, and Flame Indicators and then answer the following five standard questions?

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

Next Post

I have spent the last several days attending the Florida State Fire College Live Fire Training Instructor (LFTI) course being delivered at the Oregon Public Safety Academy in Salem, Oregon. My next post will provide an overview and critique of this excellent course.

Ed Hartin, MS, EFO, MIFireE, CFO

Unanticipated smoke explosion and building collapse nearly kills three firefighters.

Portsmouth, VA Near-Miss Incident

Firefighter Eric Kirk gives a firsthand account of a near-miss incident involving a smoke explosion in the June 2009 issue of FireRescue magazine. On a December morning in 2007, firefighters in Portsmouth, Virginia responded to a fire in a church. On arrival, the building was well involved and defensive operations were initiated to protect exposures and confine the fire. Over the course of the fire, smoke extended into an attached, three-story, brick building and formed a flammable fuel/air mixture. Subsequent extension of flames from the church to the interior of the exposure resulted in ignition and explosive combustion of this fuel (smoke)/air mixture.

Incident Photos from PilotOnline.com

Smoke Explosion

This post expands on Smoke is Fuel (Hartin, 2009), a sidebar that I wrote for FireRescue that accompanies Eric’s article examining the Portsmouth, VA smoke explosion incident.

Smoke explosions have resulted in three firefighter fatalities in the United States since 2005, two in Wyoming (see NIOSH Report F2005-13) and one last year in Los Angeles California (NIOSH report pending). In addition, there have been a number of near miss incidents including this one in Virginia and another in Durango, Colorado (see NIOSH Report F2008-02)However, many firefighters have not heard of or misunderstand this fire behavior phenomenon.

The terms backdraft and smoke explosion have typically been used to describe explosions resulting results from confined and rapid combustion of pyrolysis and unburnt products of incomplete combustion. Describing a backdraft incident at a Chatham, England Mattress Store in 1975, Croft (1980) states “this is not an entirely new phenomenon, the first formal description of what have been called ‘smoke explosions’ having been given in 1914” (p. 3).

As an explanation of many contradictory statements in reference to explosions that are reported to have occurred in burning buildings, where it is also testified that explosives were non-existent, we may cite so-called “smoke explosions.”

Distinct from, yet closely allied with explosions of inflammable dust, are explosions caused by the ignition of mixtures of air with the minute particles of unconsumed carbon and invisible gaseous matter in smoke from the imperfect combustion of organic substances…

These “smoke explosions” frequently occur in burning buildings and are commonly termed “back draughts” or “hot air explosions” (Steward, 1914).

As discussed in my earlier post, Fires and Explosions, the term Smoke Explosion was a synonym for Backdraft. In fact, if you look up the definition of smoke explosion in the National Fire Protection Association (NFPA) 921 (2008) Guide for Fire and Explosion Investigation, it says “see backdraft” (p. 921-15). However, today it identifies a different, and in many respects more dangerous extreme fire behavior phenomenon. Smoke (or Fire Gas) Explosion is described in fire dynamics textbooks such as Enclosure Fire Dynamics (Karlsson and Quintiere) and An Introduction to Fire Dynamics (Drysdale) and Enclosure Fires (Bengtsson). Of these, the text Enclosure Fires by Swedish Fire Protection Engineer Lars-Göran Bengtsson provides the best explanation of how conditions for a smoke explosion develop. However, this phenomenon is less well known among firefighters and fire officers. In fact many well known fire service authors continue to use backdraft and smoke explosion interchangeably.

A smoke or fire gas explosion occurs when unburned pyrolysis products accumulate and mix with air, forming a flammable mixture and introduction of a source of ignition results in a violent explosion of the pre-mixed fuel gases and air. This phenomenon generally occurs remote from the fire (as in an attached exposure) or after fire control.

Conditions Required for a Smoke Explosion

The risk of a smoke explosion is greatest in compartments or void spaces adjacent to, but not yet involved in fire. Infiltration of smoke through void spaces or other conduits can result in a well mixed volume of smoke (fuel) and air within its flammable range, requiring only a source of ignition.

Smoke explosions create a significant overpressure as the fuel and air are premixed. Several factors influence the violence of this type of explosion:

• The degree of confinement (more confinement results in increased overpressure)
• Mass of premixed fuel and air in the compartment (more premixed fuel results in a larger energy release)
• How close the mixture is to a stoichiometric concentration (the closer to an ideal mixture the faster the deflagration)

For additional information on transient, explosive, fire phenomena see earlier posts: Gas Explosions and Gas Explosions Part 2.

Indicators Smoke Explosion Potential

It is very difficult to predict a smoke explosion. However, the following indicators point to the potential for this phenomenon to occur.

• Ventilation controlled fire (inefficient combustion producing substantial amounts of unburned pyrolysis products and flammable products of incomplete combustion)
• Relatively cool (generally less than 600^o C or 1112^o F) smoke
• Presence of void spaces, particularly if they are interconnected
• Combustible structural elements
• Infiltration of significant amounts of smoke into uninvolved exposures

Mitigating the Hazard

As with recognizing the potential for a smoke explosion, mitigation can also be difficult. The gases are relatively cool, so application of water into the gas layer may have limited effect. Tactical ventilation to remove the smoke is the only way to fully mitigate the hazard and establish a safe zone. However, use care not to create a source of ignition (such as the sparks created when using an abrasive blade on a rotary saw).

The best course of action is to prevent infiltration of smoke into uninvolved spaces using anti-ventilation (confinement) tactics. Anti-ventilation is the planned and systematic confinement of heat, smoke, and fire gases, and exclusion of fresh air (from the fire). In this case, anti-ventilation may involve pressurizing the uninvolved are to prevent the spread and accumulation of smoke.

Ed Hartin, MS, EFO, MIFIreE, CFO

References

Bengtsson, L. (2001). Enclosure fires. Karlstad, Sweden: Räddnings Verket.

Croft, W. (1980) Fires involving explosions-a literature review. Fire Safety Journal, 3(1), 3-24.

Drysdale, D. (1998). An introduction to fire dynamics (2^nd ed.). New York: John Wiley & Sons.

Hartin, E. (2009, June). Smoke is fuel. FireRescue, 27(6), 54.

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

Kirk, E. (2009, June). Sudden blast: Unanticipated smoke explosion & building collapse nearly kills 3 firefighters. FireRescue, 27(6), 52-54.

National Fire Protection Association. (2008). NFPA 921 Guide for fire and explosion investigations. Quincy, MA: Author.

National Institute for Occupational Safety and Health (NIOSH). (2006) Death in the Line of Duty Report F2005-13. Retrieved June 22, 2009 from http://www.cdc.gov/niosh/fire/pdfs/face200513.pdf

National Institute for Occupational Safety and Health (NIOSH). (2009) Death in the Line of Duty Report F2008-02. Retrieved June 22, 2009 from http://www.cdc.gov/niosh/fire/pdfs/face200803.pdf

Steward, P. (1914). Dust and smoke explosions, NFPA Quarterly 7, 424-428.

Congratulations!

I would like to offer my congratulations to my two friends and colleagues Inspector John McDonough, ASFM of the New South Wales Fire Brigades and Acting Inspector Shan Raffel, CIFireE, EngTech, ASFM of Queensland Fire Rescue on receiving the Australian Fire Service Medal (AFSM) for distinguished service to their nation’s fire service. This is the second accolade for Shan in the last several months as he was recognized as a Companion of the Institution of Fire Engineers (IFE) for his work as national president and his tireless work for IFE Australia. Outstanding work gentlemen, honors well deserved!

Figure 1 ASFM Recpients Shan Raffel (left) and John McDonough (right)

B-SAHF! Master Your Craft

In Reading the Fire: B-SAHF, I introduced the B-SAHF (Building, Smoke, Air Track, Heat, and Flame) conceptual framework for reading the fire and have subsequently provided a series of video clips and photos to provide an opportunity to exercise your skill in reading the fire. While looking at video, photos (and actual incidents) may help build your knowledge and skill, different types of practice and knowledge building can also further your professional development.

Concept Maps

A concept map is a graphic tool for representing knowledge (Novak & Cañas, 2008). The map illustrates concepts and their relationships to one another (similar to an electrical circuit diagram or road map). Concept maps use a hierarchical form (similar to an organizational chart) with general concepts at the top and details further down. Mind maps are a similar tool often used in brainstorming that use a radial hierarchy with a tree-like hierarchy branching out from the center. I draw on both of these approaches in describing fire behavior indicators. A radial hierarchy is used as the foundation, but other relationships are illustrated and concepts can be interconnected in a variety of different ways.

A key step in improving your ability to read the fire is to think about what you should be looking for. Identifying key indicators and thinking about what they mean can be an important step in developing and improving your knowledge and skill. I find that this is an ongoing process as I continue to add to and refine my fire behavior indicators concept map. This map is not a fireground tool or a checklist of things to look for, but serves as a representation of my understanding and learning. While I am willing to share this map (Ed’s B-SAHF Map v5.2.1), it is more useful for you to build your own, representing your own understanding of these indicators and concepts.

Concept maps can be created using a pencil and paper, Post-It notes and an easel pad or white board, or using a computer with drawing software or a program specifically created for concept mapping. At one point or another, I have used each of these tools and find that they all have advantages and disadvantages. The tools you use are not as important as the mental process of collaborating with others and creating your map.

The Starting Point

Without getting bogged down an a long discussion of the educational and psychological foundations for concept mapping, it is important to understand that development of concept maps supports meaningful rather than rote learning. Rote learning often involves simple memorization. Meaningful learning requires three conditions (Ausubel, 1963).

• Concepts must be clear and presented with common language and examples connected to the learner’s prior knowledge.
• The learner must have relevant prior knowledge. Note that the learner does not require expertise, but needs sufficient knowledge to make sense of the concepts involved.
• Most importantly, the learner must choose to learn in a meaningful way.

Many firefighters struggle with creating mind maps (at first) because much of fire service training focuses on rote learning. However, I find that this challenge can easily be overcome if firefighters recognize the value of exploring the key fire behavior indicators and their relationships to one another.

Developing a concept map starts with a focus question that specifies the problem or issue that the map is intended to help resolve. The fire behavior indicators (FBI) concept map starts with the following focus question:

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

It is important to remember that a concept map is never finished. After you develop the first draft, it is always necessary to revise the map to increase clarity or add important concepts that you discover as work continues. For example, my FBI Concept Map is on Version 5.2.1, indicating five major revisions and 21 minor revisions or additions over seven years!

Knowledge Soup

The best concept maps are not developed in a vacuum. Collaboration with others can help us identify additional information and provides ideas that we may not have thought of on our own. For example, the current version of my FBI concept map started as my collaboration with Shan Raffel. However, it has evolved to include suggestions from hundreds of CFBT course participants.

Propositions or ideas developed by a group of learners may be thought of as ingredients in a kind of “knowledge soup” (Cañas, Ford, Hayes, Brennan, & Reichherzer, 1995, p. 4). The learners share the ingredients and each cook their own variation on the soup by constructing their own understanding. One way to approach this is to brainstorm key concepts and ideas before beginning the process of organizing the information and drawing the map.

Technology and Information Sharing

We have an advantage today that firefighters in previous generations did not have. Technology provides unparalleled opportunity for collaboration and learning. For example, this blog provides me with an opportunity to communicate and share information with firefighters around the world in a matter of minutes. In addition to my twice weekly blog posts, micro-blogging using the CFBT-US Twitter page provides a simple and easy method to rapidly share information on a daily (and in some cases hourly) basis.

Recently I have been reading a series of blog posts titled 31 Days to Build a Better Blog on Problogger. This stimulated my thinking about different ways to leverage technology to share information within the fire service and more particularly the compartment fire behavior community. Twitter may provide a simple means for collecting the ingredients needed for the knowledge soup necessary to develop and improve our respective fire behavior indicators concept maps.

This process could be started posting a question focused on one element of the FBI Concept map such as: What key building factors that impact on fire behavior can be used as indicators of current and predicted fire behavior? Readers can then respond (Tweet Back) with brief statements (no more than 140 characters) that identify the factors. All readers would then have access to this information when constructing the Building Indicators segment of their FBI Concept Map.

Another challenge is actually drawing the concept map (some of us are more graphically inclined or skilled than others). Bubble.us is a simple and easy to learn tool that provides a way to organize information as a concept map and share the work with others by e-mail, on the web, or embedded in a web page.

Figure 2. Bubbl.us Concept Map

Use of this software is free (you simply visit the bubbl.us web page, sign up and start creating your map. You can share your map with others to read or you can give them permission to edit the map. While I have not used this software extensively, it appears to be extremely easy to use and an excellent tool to simplify the process of drawing concept maps.

Where to from Here?

All very interesting, but how does this help us improve our ability to read the fire? Originally I had thought about using the “31 Days” concept to reading the fire. However, it will likely take a bit longer than that.

My next post will propose that we begin with an examination of building factors that influence fire behavior and which may serve as useful indicators in situational assessment. In the mean time, visit the CFBT-US Twitter page and respond to the question about building factors! Follow me for regular updates (you can also subscribe to an RSS Feed to receive information in a feed reader or via e-mail).

Each month I will move to the next element in the B-SAHF organizing scheme for fire behavior indicators until we have completed the entire FBI concept map. However, feel free to work ahead!

Ed Hartin, MS, EFO, MIFireE, CFO

References

Ausubel, D. (1963). The psychology of meaningful verbal learning. New York: Grune and Stratton.

Cañas,A., Ford, K., Hayes, P., Brennan, J., & Reichherzer,T. (1995) Knowledge construction and sharing in Quorum. Retrieved June 7, 2009 from http://www.ihmc.us/users/acanas/Publications/AIinEd/AIinEd.pdf

Novak. J. & Cañas, A. (2008). The theory underlying concept maps and how to construct and use them. Retrieved June 7, 2009 from http://cmap.ihmc.us/Publications/ResearchPapers/TheoryUnderlyingConceptMaps.pdf

Application of the B-SAHF (Building, Smoke, Air Track, Heat, & Flame) organizing scheme for critical fire behavior indicators to photographs or video of structure fires provides an excellent opportunity to develop your knowledge of fire behavior and skill in reading the fire.

Residential Fire

Shortly after 1730 hours on May 19, 2008, companies from the Baltimore City Fire Department were dispatched for a residential fire at 321 S Calhoun Street. Responding companies observed a large column of smoke from several blocks away.

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

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

1. Watch the next 60 seconds (first two minutes) of the video clip and consider the following questions:
2. What changes in fire behavior indicators have you observed in the second 60 seconds?

Watch the remainder of the video and see if your assessment matches actual incident conditions. Additional video of this incident can be viewed on the WBAL-TV { http://www.wbaltv.com/video/19514614/index.html ] web site.

Remember the Past

As mentioned in earlier posts, I am involved in an ongoing project to assemble and examine narratives, incident reports, and investigations related to extreme fire behavior events. Unfortunately many of these documents relate to line of duty deaths. As I read through the narratives included in the United States Fire Administration line of duty death database and annual reports on firefighter fatalities, I realized that every week represents the anniversary of the death of one or more firefighters as a result of extreme fire behavior.

While some firefighters have heard about the incidents involving multiple fatalities, others have not and most do not know the stories of firefighters who died alone. In an effort to encourage us to remember the lessons of the past and continue our study of fire behavior, I will occasionally be including brief narratives and links to NIOSH Death in the Line of Duty reports and other documentation in my posts.

May 30, 1999
Firefighter Lewis Jefferson Matthews
Firefighter Anthony Sean Phillips, Sr.
District of Columbia Fire Department

District of Columbia Fire Department Firefighter Matthews and Firefighter Phillips were members of two different engine companies working on the first floor of a townhouse that was experiencing a fire. Both crews had entered the front door of the townhouse at street level. The fire was confined to the basement. The basement, at grade at the rear of the structure, was opened by a truck company and a small fire was observed. A company officer at the basement door requested permission to hit the fire but his request was denied by the incident commander since he knew that crews were in the building and he did not want to have an opposing hose stream situation. The fire grew rapidly and extended up the basement stairs into the living areas of the townhouse where Firefighter Matthews, Firefighter Phillips, and other firefighters were working. With the exception of Firefighter Matthews and Firefighter Phillips, all firefighters exited

the building after the progress of the fire made the living area of the townhouse untenable. On the exterior of the building, firefighters realized that Firefighter Matthews was not accounted for. Firefighters reentered the building and followed the sound of a PASS device. They removed the firefighter with the activated PASS to the exterior of the building. Once outside, firefighters realized that the firefighter who had been rescued was not Firefighter Matthews, but was, in fact, Firefighter Phillips. The search continued and Firefighter Matthews was discovered and removed approximately 4 minutes later. Firefighter Phillips’ PASS device was of the type that is automatically activated when the SCBA is activated and it worked properly. Firefighter Matthews’ PASS was a manually activated type and it was found in the “off” position. Both firefighters received immediate medical care on the scene and were transported rapidly to hospitals. Firefighter Phillips was pronounced dead upon arrival at the hospital and Firefighter Matthews died the following day, May 31, 1999. Firefighter Phillips died as the result of burns over 60 percent of his body surface area and his airway. Firefighter Matthews died as the result of burns over 90 percent of his body surface area and his airway. 2 other firefighters were injured fighting the fire. One (1) of these 2 firefighters, who suffered burns over 60 percent of his body surface area, survived and was released from the hospital in late August. At the time of his release, it was not clear if this firefighter would ever return to work. Additional information about this incident can be found in NIOSH Fire Fighter Fatality Investigation 99-F-21 and National Institute for Standards and Technology (NIST) report Simulation of the Dynamics of the Fire at 3146 Cherry Road NE, Washington D.C., May 30, 1999.

May 9, 2001
Firefighter Alberto Tirado
Passaic Fire Department, New Jersey

Firefighter Tirado and members of his department were dispatched to a report of a fire in an occupied three-story apartment building. The first-arriving engine company reported a working fire and Firefighter Tirado responded as the tiller driver of the first-arriving ladder company.

Firefighters on-scene received reports that children were trapped in the building. Firefighter Tirado and another firefighter from his company proceeded to the second floor of the building to conduct a search. A search of the second floor was conducted and all of the apartments on that floor were found to be clear. Firefighter Tirado and the other firefighter proceeded to the third floor to continue their search. On their way to the third floor, the team encountered heavy smoke and high heat. Both firefighters went back to the second-story landing. Firefighter Tirado’s partner told Firefighter Tirado to wait on the landing while he retrieved additional lighting from the apparatus.

A few minutes later, Firefighter Tirado called on the radio and said that he was trapped on the third floor. This transmission was not heard on the fireground and a second request for help was also not heard. He called a third time and reported that he was trapped on the third floor and needed help. Firefighter Tirado’s exit path had been blocked by fire, and he was unable to find his way out.

A defective throttle on the pumper supplying the initial attack line created water supply and pressure problems. Firefighters were unable to advance to the third floor to rescue Firefighter Tirado. The fire on the third floor grew to a point where it was impossible for firefighters to control it with handlines. An aerial master stream was used to darken down the fire and allow firefighters to access the third floor. After a number of attempts, Firefighter Tirado was discovered in a third-story bedroom.

The cause of death was listed as asphyxiation. Firefighter Tirado’s carboxyhemoglobin level was found to be 65%. The fire was caused by an unsupervised 12 year old girl that was attempting to light a stove. The children that were reported trapped were actually out of the building.

For additional information on this incident, refer to NIOSH Fire Fighter Fatality Investigation F2001-18.

Ed Hartin, MS, EFO, MIFireE, CFO

Application of the B-SAHF (Building, Smoke, Air Track, Heat, & Flame) organizing scheme for critical fire behavior indicators to photographs or video of structure fires provides an excellent opportunity to develop your knowledge of fire behavior and skill in reading the fire.

This video clip was recommended by Captain Virgil Hall, Tualatin Valley Fire & Rescue. Virgil is stationed at Station 64 and is one of TVF&R’s CFBT Instructors.

Residential Fire

Download and print the B-SAHF Worksheet. Consider the information provided in the short video clip. First, describe what you observe in terms of the Building, Smoke, Air Track, Heat, and Flame Indicators and then answer the following five standard questions?

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

Review the video again, watch the indicators on Side A closely, and give some thought to the following questions posed by Captain Hall:

1. How did the smoke and flame indicators change?
2. What did this indicate?
3. Why did these changes occur (what were the influencing factors)?

Special thanks to Captain Hall for recommending this video clip. Please feel free to contribute to this process and share or recommend video clips or photographs that will help us develop our skill in reading the fire.

Remember the Past

While some firefighters have heard about the incidents involving multiple fatalities, others have not and most do not know the stories of firefighters who died alone. In an effort to encourage us to remember the lessons of the past and continue our study of fire behavior, I will occasionally be including brief narratives and links to NIOSH Death in the Line of Duty reports and other documentation in my posts. The first narrative in this post is incomplete as this incident, resulting in the death of two members of the Houston Fire Department occured last Sunday. It is important for us to continue our efforts to understand and mitigate the complex and interrelated factors that result in firefighter fatalities occuring during structural firefighting operations.

April 12, 2009
Captain James Harlow
Firefighter Damion Hobbs
Houston Fire Department, Texas

Captain James Harlow and Firefighter Damion Hobbs of the Houston, Texas Fire Department lost their lives in the line of duty while conducting primary search in a single family dwelling on the morning of April 12, 2009. Preliminary information indicates that Captain Harlow and Firefighter Hobbs were trapped by rapid fire progress, possibly influenced by wind. The Houston Fire Department, Texas State Fire Marshal, and National Institute for Occupational Safety and Health (NIOSH) are all investigating this incident. More information will be posted as it becomes available.

April 11, 1994
Lieutenant Michael Mathis
Private William Bridges
Memphis Fire Department, Tennessee

On April 11, Lt. Michael Mathis and Private William Bridges of the Memphis (TN) Fire Department were killed when they became trapped and overcome by smoke during a fire on the ninth floor of a high rise building. Two civilians also died in the arson fire. Lt. Mathis became disoriented when he was caught in rapidly spreading fire conditions on the fire floor, burning him and causing his SCBA to malfunction. He found his way into a room on the ninth floor were he was later discovered by other fire crews with his SCBA air depleted. Private Bridges, aware that Lt. Mathis was unaccounted for after several unsuccessful attempts to contact him by radio, left a safe stairwell where he had been attempting to fix a problem with his own SCBA. Investigators believe Bridges was trying to locate Lt. Mathis. Bridges became entangled in fallen cable TV wiring within a few feet of the stairwell, and died of smoke inhalation after depleting his SCBA supply. A Memphis Fire Department investigation found many violations of standard operating procedures by companies on the scene, including crews taking the elevator to the fire floor, problems with the incident command system and coordination of companies, operating a ladder pipe with crews still on the fire floor, and a failure of personnel, including Lt. Mathis and Private Bridges, to activate their PASS devices.

April 16, 2007
Firefighter-Technician I Kyle Robert Wilson
Prince William County Department of Fire and Rescue, Virginia

Technician Wilson was assigned to Tower 512, a ladder company. Tower 512 was dispatched to a reported house fire at 0603 hours. The Prince William County area was under a high wind advisory as a nor’easter moved through the area. Sustained winds of 25 miles per hour with gusts up to 48 miles per hour were prevalent in the area at the time of the fire dispatch.

Initial arriving units reported heavy fire on the exterior of two sides of the single-family house, and crews suspected that the occupants were still inside the house sleeping because of the early morning hour. A search of the upstairs bedroom was conducted by Technician Wilson and his officer. A rapid and catastrophic change of fire and smoke conditions occurred in the interior of the house within minutes of Tower 512’s crew entering the structure. Technician Wilson became trapped and was unable to locate an immediate exit. “Mayday” radio transmissions of the life-threatening situation were made by crews and by Technician Wilson. Valiant and repeated rescue attempts to locate and remove Technician Wilson were made by the firefighting crews during extreme fire, heat, and smoke conditions. Firefighters were forced from the structure as the house began to collapse on them and fire conditions worsened. Technician Wilson succumbed to the fire and the cause of death was reported by the medical examiner to be thermal and inhalation injuries.

An extensive report on this incident is available from the Prince William Department of Fire and Rescue: Technician Kyle Wilson LODD Report.

For additional information regarding this incident, please refer to NIOSH Fire Fighter Fatality Investigation and Prevention Program Report F2007-12.

Ed Hartin, MS, EFO, MIFireE, CFO

Application of the B-SAHF (Building, Smoke, Air Track, Heat, & Flame) organizing scheme for critical fire behavior indicators to photographs or video of structure fires provides an excellent opportunity to develop your knowledge of fire behavior and skill in reading the fire.

This post uses a short video clip from Providence, RI to provide an opportunity to practice reading the fire.

Taxpayer Fire

Download and print the B-SAHF Worksheet. Consider the information provided in the short video clip. First, describe what you observe in terms of the Building, Smoke, Air Track, Heat, and Flame Indicators. Second, 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

In addition give some thought to the following four questions focused specifically on this incident:

1. Where do you think the fire is located? Why?
2. Do you observe any changes in conditions? What might these changes indicate?
3. What avenues of fire spread would be of concern? How does this relate to building factors?
4. It appears that horizontal ventilation is being conducted by interior crews on Floor 2, Side A. How is this likely to influence interior conditions and fire behavior?

Ed Hartin, MS, EFO, MIFireE, CFO

Fifteen years ago tomorrow, three members of the Fire Department of the City of New York (FDNY) lost their lives while conducting search in a three story apartment building located at 62 Watts Street in Manhattan. Captain Drennan and Firefighters Young and Seidenburg were trapped in a stairwell by rapid fire progression that occurred as other companies forced entry into the fire apartment on the floor below.

The Case

This case study was developed using a paper written by Richard Bukowski (1996) of the National Institute for Standards and Technology (NIST) Building and Fire Research Laboratory (BFRL). The FDNY requested the NIST assistance in modeling this incident to develop an understanding of the extreme fire behavior phenomena that took the lives of Captain Drennan and Firefighters Young and Seidenburg.

At 1936 hours on March 28, 1994, FDNY responded to a report of heavy smoke and sparks from a chimney of a three-story apartment building at 62 Watts Street (see Figure 1) in Manhattan. On arrival companies observesd smoke from the chimney, but no other evidence of fire. The first due engine and truck companies stretched a hoseline to the first floor unit and vertically ventilated over the stairwell.

Figure 1. 62 Watts Street-Side A

Working as the inside team of the second due truck company, Captain John Drennan (Ladder 5), Firefighter James Young, and Firefighter Christopher Seidenburg (both detailed from Engine 24 to Ladder 5) went to the second floor to begin primary search of the upper floors. At the doorway to the second floor apartment unit they were trapped by an explosion and rapid fire progression from the first floor apartment up the common stairwell. Both firefighters died within 24 hours as a result of thermal injuries. Captain Drennan survived for 40 days in the burn unit before succumbing to his injuries.

Building Information

The fire occurred in a 6.1 m (20′) x 14 m (46′), 3 ½ story apartment building of ordinary (Type III) construction, containing four dwelling units (the basement apartment was half below grade). Each unit had a floor area of slightly less than  81.7 m² (880 ft²). The basement unit had its own entrance and the units on Floors 1-3 were served by a common stairwell on Side D of the building (see Figure 1). Exposure B was an attached building identical to the fire structure. Exposure D was a similar structure. Neither exposure was involved.

Figure 2. Floor Plan-First Floor Apartment

Note: Adapted from Modeling a Backdraft Incident: The 62 Watts St. (NY) Fire.

The building was originally built in the late 1800s and had undergone numerous renovations. Recent renovations involved replacement of plaster and lath compartment linings with drywall over wood studs and lowering of the ceiling height from 2.8 m (9’3″) to 2.5 m (8’4″). All apartments had heavy wood plank flooring. During the latest renovation, windows and doors were replaced and extensive thermal insulation added to increase energy efficiency. The building was originally heated with the use of multiple fireplaces in each apartment. However, most of these had been sealed shut. However, the fireplace in the living room of the first floor apartment (unit of origin) was operable and had a 0.209 m² (2.25 ft²) flue.

All apartments had similar floor plans (differences resulting from location of the stairwell). The floor plan of the first floor apartment (unit of origin) is illustrated in Figure 2. Each apartment consisted of a living room, kitchen, bathroom, and bedroom. The first floor unit had an office constructed within the bedroom.

The structure had a flat roof with a scuttle and skylight over the stairwell.

The Fire

The occupant left the first floor apartment at 1825 hours, leaving a plastic trash bag on top of the gas fired kitchen range (see Figure 2). Investigators deduced that the bag was ignited by heat from the pilot light. Fire extended from the bag of trash to several bottles of high alcohol content liquor located on the counter adjacent to the stove. The fire progressed into the growth stage, involving other fuel packages within the apartment. The apartment was tightly sealed with the only sources of ventilation being the open fireplace flue and minimal normal building ventilation.

Weather Conditions

The weather was 10^o C (50 ^o F) with no appreciable wind.

Conditions on Arrival

On arrival companies observed smoke from the chimney of the apartment building, but no other signs of fire from the exterior.

Firefighting Operations

The outside team from the first due truck went to the roof and opened the scuttle over the stairwell while the first arriving engine company stretched a hoseline to the interior and prepared to make entry into the first floor apartment along with the inside team from the ladder company. Ladder 5 was the second due truck. The inside team from Ladder 5, Captain Drennan, Firefighter Young, and Firefighter Seidenburg, went to the second floor to begin primary search.

When the first due engine and truck forced the door to the first floor apartment they observed a pulsing air track consisting of an inward rush of air followed by an outward flow of warm (not hot) smoke. This single pulsation was followed by a large volume of flame from the upper part of the door and extending up the stairwell.

Figure 3. 3D Cutaway View of 62 Watts Street

Note: Adapted from Modeling a Backdraft: The 62 Watts Street Incident.

The crews working on Floor 1 were able to escape the rapid fire progression, but Ladder 5’s inside team was engulfed in flames which filled the stairwell. Flames extended from the doorway of the first floor apartment through the stairwell and vented out the scuttle opening and skylight. This flaming combustion continued in excess of 6 minutes 30 seconds. The intense fire in the stairwell severely damaged the stairs and melted the wired glass in the skylight.

Questions

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

1. Other than smoke and sparks from the chimney, what B-SAHF indicators might have been present and visible from the exterior or at the doorway that may have provided an indication of conditions inside the apartment?
2. What do you make of the observations of the company making entry to the first floor apartment for fire attack? Is this consistent with your understanding of backdraft indicators? Why or why not?
3. What steps can you take when making entry if you suspect that the fire is ventilation controlled? How would this change if you suspected or saw indicators of potential backdraft conditions?
4. Firefighters often identify vertical ventilation when given a scenario where backdraft indicators are present. If there is value (savable people or property) and the fire is on a lower floor (as it was in the Watts Street incident), what tactical options are available to mitigate the hazards of potential backdraft conditions?

Analysis and Computer Modeling

My next post will examine the results of this investigation and how the computer modeling performed by NIST contributes to our understanding of the events that took the lives of Captain Drennan and Firefighters Young and Seidenburg.

Ed Hartin, MS, EFO, MIFIreE, CFO

My last post examined National Institute for Standards and Technology (NIST) tests of wind control devices to mitigate hazards presented during wind driven compartment fires (Fire Fighting Tactics Under Wind Driven Conditions). Heat release rate (HRR)  data from Experiment 1 (baseline test with no wind) and Experiment 3 (wind driven) illustrates the dramatic influence of increasing ventilation to a ventilation controlled fire and even more dramatic impact when increased ventilation is coupled with wind (see Figure 1). This post posed several questions related to the HRR data from these experiments.

Figure 1. Heat Release Rates in Experiments 1 (Baseline) and 3 (Wind Driven)

Note: Adapted from Firefighting Tactics Under Wind Driven Conditions.

Questions

Examine the HRR curves in Figure 1 and answer the following questions:

• What effect did deployment of the wind control device have on HRR and why did this change occur so quickly?
• How did HRR change when the wind control device was removed and why was this change different from when the window was vented?
• What factors might influence the extent to which HRR changes when ventilation is increased to a compartment fire in a ventilation controlled burning regime?

Answers: Application of the wind control device rapidly decreased heat release rate from approximately 19 MW to 5 MW. With the window covered, the fire lacked sufficient oxygen to maintain the higher rate of HRR. As oxygen was quickly consumed (and oxygen concentration was decreased) by the large volume of flaming combustion in the compartments, heat release rate was rapidly reduced.

As with the change in HRR when the window was vented, removal of the wind control device resulted in an extremely rapid increase in HRR as additional oxygen was provided to the ventilation controlled fire inside the structure. In this case, the increase was even more significant with the peak HRR reaching approximately 32 MW. Examination of the oxygen concentration curve provides a hint of why this might have been the case (see Figure 2). The oxygen concentration was higher before the window was vented than when the wind control device was removed. The more rapid and greater rise in HRR is likely a result of the extent to which the fire was ventilation controlled and the available concentration of gas phase fuel. After the wind control device was removed, note that the oxygen concentration increased sharply (which relates to the rapid increase in HRR), followed by a rapid decrease as ventilation was inadequate to maintain that rate of combustion.

Figure 2. Oxygen Concentration in the Bedroom

Note: Adapted from Firefighting Tactics Under Wind Driven Conditions.

Practical Application

The results of the NIST research are extremely interesting to students of fire behavior. However, it is essential that we be able to transform this information into knowledge that has practical application. This gives rise to three fundamental questions:

• How do changes in ventilation influence fire behavior? Note that this is always a concern, not just under wind conditions!
• What impact will wind have if the ventilation profile changes?
• What tactical options will be effective in mitigating hazards presented by extreme fire behavior under wind driven conditions?

It is important to consider air track and the flow path from inlet to exhaust opening and the potential consequences of introducing air under pressure without (or with an inadequate) exhaust opening. Both can have severe consequences!

Tactical Problem

One good way to wrestle with the influence of wind on compartment fire behavior is to put it into a realistic context. In the following tactical problem you will be presented with an incident scenario and a series of questions. Apply what you have learned and consider how you would approach this incident.

Resources: You have what you have! Use your normal apparatus assignment and staffing levels when working through this tactical problem.

Weather Information: Conditions are clear with a temperature of 20^o C (68^o F) and a 24 kph (15 mph) wind out of the Northwest.

Dispatch Information: You have been dispatched to a residential fire at 0700 on a Sunday morning. The caller reported seeing smoke from a house at 1237 Lakeview Drive. After companies go enroute, the dispatcher provides an update that she is receiving multiple calls for a fire at this location.

Conditions on Arrival: Approaching the incident location you observe a moderate volume of medium gray smoke from a wood frame, single family dwelling (most structures in this area are of lightweight construction). Smoke is blowing towards the A/D corner of the structure. As illustrated in Figure 3, smoke is visible from the front entry (window and door) of the house and it appears that smoke is showing from Side C as well. On closer examination, you observe that the upper level of the windows on Side A are stained with condensed pyrolysis products, but are intact.

Figure 3. View from Side A

360^o Reconnaissance: Moving down Side B, you observe a substantial body of fire in the center of the house. Smoke is pushing from around several sliding glass doors on Side B (see Figure 4) and flames are visible in the upper layer. The glass in the sliding doors is blackened and cracked, but is still intact. Smoke is also visible from around a large window on Side B Floor 2. Smoke discharge on Side B is swirling and being pushed up over the roof by the wind.

Figure 4. View from the BC Corner

Proceeding around the structure to Sides C and D, you observe a small amount of smoke pushing out from around the windows on Side D.

Questions: The first set of questions deals with size-up and development of an initial plan of action.

• What B-SAHF indicators do you observe in Figures 2 and 3?
• What stage(s) of fire development is (are) likely to exist in the structure?
• What burning regime is the fire in?
• How is the fire likely to develop in the time that it will take to develop and implement your incident action plan?
• Would you have given orders to your crew (or would they have taken pre-planned standard actions) based on your observation of conditions on Side A (Figure 1)? If so what would have been done? Why?
• Would your action plan have changed based on your observations from the B/C corner? What would you do differently? Why?
• What is your action plan at this point? Do you have sufficient resources? What orders would you give the first alarm companies? What actions would you have your crew take? Why?

Your action plan is dependent on size-up and assessment of incident conditions.  Variation in conditions may result in a change in the priority or sequence of tactical action. Would your action plan have been different if the dispatcher had indicated that the caller was trapped in the house? If it would have, what would you have done differently? Why?

Things to Think About

This tactical problem presents a number of challenges. Click on the link to examine the Floor Plan and then consider the following questions:

• What conditions would firefighters have encountered if they made entry through the door on Side A (front door)? Why?
• How would these conditions have changed if glass in one or more of the sliding doors on Side B had failed after firefighters had made entry? Why?
• What conditions would have resulted if the glass in one or more of the sliding doors on Side B had failed and the door on Side A was not open? Why?
• What options for fire attack and tactical ventilation would have been effective in this situation? Would your choice fire attack and tactical ventilation location, sequence, and coordination have varied based on the report of occupants? Why?
• How did your knowledge of the results of the NIST tests on wind driven fires impact your understanding of this incident? How did this understanding influence your tactical decision-making?

It is important to practice strategic and tactical decision-making. However, it is also important to think about how and why we make these decisions. This meta-learning (learning about our learning) has a significant impact on our professional development and ability to learn our craft.

Remember the Past

As discussed in previous posts, it is important to honor the sacrifices of firefighters who have died in the line of duty and not lose lessons learned as time passes. The following narratives were taken from the United States Fire Administration (USFA) reports on Firefighter Line of Duty Deaths (1994 and 2004).

March 29, 1994
Captain John Drennan, 49, Career
Firefighter James Young, 31, Career
Firefighter Christopher Seidenburg, 25, Career
Fire Department of the City of New York, New York

On March 29, three firefighters trapped in the stairwell of a brownstone were burned when they were enveloped in fire while attempting to force their way through a heavy steel door to a second floor apartment. Captain John Drennan, Firefighter James Young, and Firefighter Christopher Seidenburg of the New York City Fire Department were conducting a search when the hot air and toxic gases that collected in the stairwell erupted into flames as other fire crews forced entry into the first floor apartment where the fire had originated. The fire exhibited characteristics of both a backdraft and a flashover. Firefighter Young, in the bottom position on the stairs, was burned and died at the scene. Firefighter Seidenberg and Captain Drennan were rescued by other firefighters. They were transported to a burn unit with third and fourth degree burns over 50 of their bodies. Seidenburg died the next day. Drennan passed away several weeks later. The fire cause was determined to be a plastic bag left by the residents on top of the stove of the floor apartment.

For additional information on this incident see:

Bukowski, R. (1996). Modeling a backdraft: The 62 Watts Street incident. Retrieved March 14, 2009 from http://fire.nist.gov/bfrlpubs/fire96/PDF/f96024.pdf

March 21, 2003 – 0850
Firefighter Oscar “Ozzie” Armstrong, III, Age 25, Career
Cincinnati Fire Department, Ohio

Firefighter Armstrong and the members of his fire company responded to the report of a fire in a two-story residence. The first fire department unit on the scene, a command officer, reported a working fire.

Firefighter Armstrong assisted with the deployment of a 350-foot, 1-3/4-inch handline to the front door of the residence. Once the door was forced open, firefighters advanced to the interior. The handline was dry as firefighters advanced; the hose had become tangled in a bush.

As the line was straightened and water began to flow to the nozzle, a flashover occurred. The firefighters on the handline left the building and were assisted by other firefighters on the front porch of the residence. All firefighters were ordered from the building, air horns were sounded to signal a move from offensive to defensive operations.

Several firefighters saw Firefighter Armstrong trapped in the interior by rapid fire progress. These firefighters advanced handlines to the interior and removed Firefighter Armstrong. A rapid intervention team assisted with the rescue.

Firefighter Armstrong was severely burned. He was transported by fire department ambulance to the hos­pital where he later died.

The origin of the fire was determined to be a pan of oil on the stove.

For additional information on this incident see:

National Institute for Occupational Safety and Health (NIOSH). (2005). Death in the line of duty report F2003-12. Retrieved March 14, 2009 from http://www.cdc.gov/niosh/fire/pdfs/face200312.pdf

Laidlaw Investigation Committee. (2004)Line of duty death enhanced report Oscar Armstrong III March 21, 2004. Retrieved March 14, 2009  from http://www.iafflocal48.org/pdfs/enhancedloddfinal.pdf

Ed Hartin, MS, EFO, MIFireE, CFO

References

Madrzykowski, D. & Kerber, S. (2009). Fire fighting tactics under wind driven conditions. Retrieved (in four parts) February 28, 2009 from http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part1.pdf; http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part2.pdf;http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part3.pdf;http://www.nfpa.org/assets/files//PDF/Research/Wind_Driven_Report_Part4.pdf.

United States Fire Administration (USFA). (1995) Analysis report on firefighter fatalities in the United States in 1994. Retrieved March 14, 2009 from http://www.usfa.dhs.gov/downloads/pdf/publications/ff_fat94.pdf

United States Fire Administration (USFA). (2005). Frefighter fatalities in the United States in 2004. Retrieved March 14, 2009 from http://www.usfa.dhs.gov/downloads/pdf/publications/fa-299.pdf

What is Extreme?

There is some debate about the use of the term extreme fire behavior (some of my colleagues indicate that processes such as flashover is not “extreme” but simply “normal” fire behavior). I contend that flashover would potentially be a normal part of fire development, but is also extreme, at least in the context that we are using the word. As defined in the wildland firefighting community:

“Extreme” implies a level of fire behavior characteristics that ordinarily precludes methods of direct control action. One or more of the following is usually involved: high rate of spread, prolific crowning and/or spotting, presence of fire whirls, strong convection column. Predictability is difficult because such fires often exercise some degree of influence on their environment and behave erratically, sometimes dangerously (National Wildfire Coordinating Group Glossary)

In the structural firefighting environment, occurrence of flashover (particularly while firefighters are operating inside the compartment) fits substantially with the description of extreme used by wildland firefighters.

Classification and Understanding

Ontology may be described as definition of a formal representation of concepts and the relationships between those concepts. An ontology provides a shared vocabulary. Unfortunately we do not have a well developed ontology of fire behavior phenomenon and many types of phenomena have more than one definition. As with the use of the word extreme, there is some debate about the need to classify phenomena as being this or that (e.g., flashover or backdraft). I take the position that it is useful (but difficult as we do not have a common classification scheme or ontology). But, I think that it is still worth the effort.

This is a substantive topic for a later post. This post will examine a type of fire gas ignition phenomena that has been involved in a number of incidents in recent years resulting in near misses, injuries, and fatalities.

Fire Gas Ignitions

In a previous post, I posed the question: Backdraft or Smoke Explosion?. This post used a video clip to open a discussion of the difference between these two phenomena. A smoke (or fire gas) explosion is a type of fire gas ignition, but there are a number of other types of fire gas ignition that present a hazard during firefighting operations.

All fire gas ignitions (FGI) involve combustion of accumulated unburned pyrolysis products and flammable products of incomplete combustion existing in or transported into a flammable state (Grimwood, Hartin, McDonough, & Raffel, 2005). In a smoke explosion, ignition of a confined mass of smoke gases and air that fall within the flammable range results in extremely rapid combustion (deflagration), producing an significant overpressure which can result in structural damage. However, what happens if the mass of gas phase fuel is not pre-mixed within its flammable range and does not burn explosively?

The general term Fire Gas Ignition, encompasses a number of phenomena that are related by the common characteristic that they involve rapid combustion of gas phase fuel consisting of pyrolizate and unburned products of incomplete combustion that are in or are transported into a flammable state. For now, let’s differentiate these phenomena from backdraft on the basis of the concentration of gas phase fuel (backdraft involving a higher concentration than fire gas ignition).

Fire gas ignition can involve explosive combustion (as in a smoke explosion) or rapid combustion that does not produce the same type of overpressure as an explosion. One such phenomenon is a flash fire. In this case, gas phase fuel ignites and burns for short duration, but does not release sufficient energy for the fire to transition to a fully developed stage (as occurs in flashover). While a flash fire may not result in flashover, the energy release is still significant and heat flux (energy transferred) can be sufficient result in damage to personal protective equipment, injury and death. This post uses a case study to examine the flash fire phenomenon.

Residential Fire

This case study is based on a near-miss incident involving extreme fire behavior during a residential fire that occurred on October 9, 2007 at 1119 William Street in Omaha, Nebraska. Special thanks to Captain Shane Hunter (Omaha Fire Department Training Officer) for sharing this post incident analysis and lessons learned.

Unlike many of the incidents used as case studies, no one died or was injured during incident operations. In this near miss incident, the firefighters and officers involved escaped without injury, but the outcome could easily have been quite different.

Weather Conditions

Weather was typical for early fall with a light breeze from the south (blowing towards Side C of the fire building).

Building Information

The fire building was a one and a half story, wood frame dwelling with a basement (see Figure 1). The attic space had been renovated into three separate compartments to provide additional living space.

Figure 1. Exterior View Side A

Figure 2. Floor 2 Layout

Conditions on Arrival

When the first company arrived they observed fire and smoke from the second floor window (see Figure 1) and reported a working fire. The doors and windows on the first floor were closed.

Firefighting Operations

What initial actions were taken? A 200′ hoseline was extended through the door located on Side A and through the living room and kitchen to the stairway to the second floor, which was located at the C/D corner of the structure (Figures 2 and 3).

Figure 5 & 6. Kitchen (view from Floor 1) and Stairwell (view from Floor 2)

What did the fire attack crew observe? The living room and kitchen were clear of smoke and the door to the second floor stairway was closed. When this door was opened and the line was advanced up the stairway to the second floor, the company assigned to fire attack encountered smoke down to floor level on the second floor. Making a left turn at the top of the stairs (see Figure 4) the Captain noted high temperature at the floor level and observed rollover at the ceiling level.

• How did the ventilation profile change when the door to second floor stairway was opened? How might this have changed fire behavior?
• What did the depth of the hot gas layer (from ceiling to floor) indicate about the ventilation profile?
• What did rollover in the center compartment indicate?

The Captain instructed the nozzle operator to apply water to the ceiling. The firefighter on the nozzle applied water in a 30^o fog pattern (continuous application). Simultaneously, a crew working on the exterior vented the second floor window on Side C (see Figures 4 and 6).

How did conditions change? The engine company working on floor 2 heard an audible, whoosh as the hot gas layer ignited producing flames down to floor level. Operation of the hoseline (30^o fog pattern) had no immediate effect. The Captain ordered the crew to retreat into the stairwell and continue water application.

• What extreme fire behavior phenomena occurred?
• What were the initiating events that caused this rapid fire progression?

Figure 4. Floor 2 Side A (Looking Towards Side A)

Figure 5. Floor 2 Side C (Looking Towards Side C)

What action was taken? While the engine company operated from the stairwell, vertical ventilation was completed over the center compartment (see Figures 4 and 5). After the creation of an exhaust opening in the roof, conditions on floor 2 became tenable and the engine crew was able to knock the fire down within several minutes.

• Why did conditions improve quickly after the creation of a vertical exhaust opening?
• What tactical options might have prevented this near miss?

Observations and Analysis

Captain Shane Hunter observed that the initial fire attack crew viewed this incident as an easy job. They thought that an attack from the unburned side would simply push the fire out the window where fire was initially showing on Side A. Why did things turn out so differently than anticipated?

In his analysis of this incident, Captain Hunter points out that there is a considerable difference between a “self-vented” fire and an adequately ventilated fire. As discussed in the April 2008 Officer’s Corner (GFES), horizontally ventilated fires are likely to remain ventilation-controlled. It is important to read the Building, Smoke, Air Track, Heat, and Flame (B-SAHF) indicators to determine the current burning regime (fuel or ventilation-controlled) and anticipate the effect of changes to the ventilation profile.

The fire in the compartment of origin reached flashover resulting in the extension of flames into the center compartment as evidenced by the observation of rollover by the Captain of the engine company performing fire attack. However, the center compartment and the compartment on Side C did not experience flashover (note the condition of contents in the center compartment in Figure 6.). If flashover did not occur in these two compartments, what happened?

In this incident, the fire gases ignited in a flash fire, but combustion did not rapidly transition to a fully developed state in the two compartments adjacent to the compartment of origin.

A flash fire rapidly increases heat release rate, temperature within the compartment and heat flux (as experienced by the fire attack crew in this incident). Like rollover, this phenomenon should not be confused with flashover as fuel in the lower region of the compartment may or may not ignite and sustain combustion. However, fire gas ignition can precede and precipitate flashover (should the fire quickly transition to the fully developed stage).

The concentration of fuel within the hot gas layer varies considerably, with higher concentrations at the ceiling. Concentrations within the flammable range most commonly develop at the interface between the hot gas layer and the cooler air below. Isolated flames (an indicator of a ventilation-controlled fire) are most commonly seen in the lower region of the hot gas layer (as there may be insufficient oxygen concentration in the upper level of the hot gas layer to support flaming combustion). Mixing of the hot gas layer and air due to turbulence increases the likelihood of a significant fire gas ignition.

• What was the ventilation profile and air track when the engine company reached the top of the stairs to begin their attack on the fire?
• How did the tactical ventilation performed from the exterior (removal of the window on floor 2, Side C) influence the ventilation profile and air track?
• What effect do you think that continuous operation of the 30^o fog stream had on conditions on floor 2?
• What combination of factors likely resulting in mixing of air and smoke (fuel) leading to the fire gas ignition that drove the fire attack crew off floor 2 and into the stairwell?

Key Considerations and Lessons Learned

This incident points to a number of key considerations and lessons learned.

• Beware the routine incident! Even what appears to be a simple fire in a small residential structure can present significant challenges and threats to your safety.
• Use the B-SAHF indicators to read the fire and consider both the stage of fire development and burning regime (fuel or ventilation-controlled) in strategic and tactical decision making.
• Flame showing is just that. Do not be lulled into a false sense of security by thinking that the fire is adequately ventilated. Read the air track indicators!
• Continue to read the fire after making entry. Smoke is fuel and hot gases overhead are a threat. Observation of isolated flames indicates a ventilation-controlled fire. Rollover often precedes flashover. Take proactive steps to mitigate the threat of extreme fire behavior.
• Recognize that ventilation-controlled fires will increase in heat release rate if additional air is introduced. Manage the ventilation profile using tactical ventilation and tactical anti-ventilation. Anticipate unplanned ventilation due to fire effects.
• Recognize that both horizontal and vertical ventilation are effective when used appropriately and coordinated with fire control. Consider the influence of inlet and exhaust opening location and size when anticipating the influence of tactical ventilation on fire behavior and conditions within the building.

Again special thanks to Captain Shane Hunter and the Omaha Fire Department for sharing the information about this incident and their work to improve firefighter safety.

Ed Hartin, MS, EFO, MIFireE, CFO