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.

Fire Behavior Indicators – A Quick Review

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

Figure 1. B-SAHF

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

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

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

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

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

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

Getting Started

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

Figure 2. Basic Building Factors

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

Developing the Detail

Expanding the map requires identification of additional detail for each of the fundamental concepts. If an idea appears to be obviously related to one of the concepts already on the map, go ahead and add it. If you are unsure of where it might go, but it seems important, list it off to the side in a staging area for possible additions. For example, area and height are important concepts related to size. However, compartmentation may be related to size or it may be a construction factor. If you are unsure of where this should appear on the map, place it in the Staging Area for now.

Figure 3. Expanding the Map

Next Steps

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

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

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

Thanks

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

Figure 4 Jason Collits and Matt Leech

Remember the Past

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

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

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

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

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

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

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

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

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

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

For additional information on this incident, see the following:

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

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

Incident Photos by Steve Spak

Ed Hartin, MS, EFO, MIFireE, CFO

References

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

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

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

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

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

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

Safety Week 2009

June 14-20, 2009 is Fire & EMS Safety, Health, and Survival Week. CFBT-US urges you to take this week to examine your own habits and behaviors and common practices in your fire service organization with a critical eye and identify ways in which you can reduce your risk and improve the effectiveness of fireground operations.

IAFC Recommendations

The International Association of Fire Chiefs (IAFC) has published a list of recommendations to encourage individual and organizational responsibility for safety.

Safety: Emergency Driving (enough is enough-end senseless death)

1. Lower speeds-stop racing to the scene. Drive safely and arrive alive to help others.
2. Utilize seat belts-never drive or ride without them.
3. Stop at every intersection-look in all directions and then proceed in a safe manner.

Health: Fire Fighter Heart Disease and Cancer Education and Prevention

1. Don’t smoke or use tobacco products.
2. Get active.
3. Eat a heart-healthy diet.
4. Maintain a healthy weight.
5. Get regular health screenings.

Survival: Structural Size-Up and Situational Awareness

1. Keep apprised of different types of building materials and construction used in your community.
2. Develop a comprehensive size-up checklist.
3. Always complete a 360° walk of the structure to collect valuable, operational decision-making information.
4. Learn the practice of reading smoke.
5. Be familiar with the accepted rules of engagement.
6. Learn your accountability system and use it.
7. Master your tools and equipment.
8. Remain calm and concentrate.

Chiefs: Be the Leader in Safety

1. Become personally engaged in safety and make it part of your strategic vision for the department.
2. Be willing to make the tough decisions regarding safety policies and practices and their implementation.
3. Hold members of the organization accountable for their safety and the safety of those with whom they work.
4. Ensure that resources are available to accomplish activities safely and effectively.

Additional Considerations

In addition to the recommendations made by the IAFC, I would like to offer several additional recommendations and revisions to the IAFC’s list.

Health: Remember that products of combustion present both short and long term health effects. Don’t breathe smoke and minimize exposure to products of combustion by using care in handling contaminated equipment and clothing and cleaning it promptly after use.

Survival: Develop a solid understanding of practical fire dynamics. In addition to understanding building construction (B) and reading smoke (S), use the entire B-SAHF (Building-Smoke, Air Track, Heat, & Flame) approach to reading the fire. Remember that size-up and dynamic risk assessment are an ongoing process conducted by everyone on the fireground!

Chiefs: Not only must you hold your members accountable. They must be able to hold you accountable as well. Lead by example!

Still Waiting to Hear from You!

In an earlier post, I encouraged you to construct a personal concept map of fire behavior indicators, starting with building factors. As a way of collaborating on this project, you can follow edhartin on Twitter and Tweet Back on this question with factors that you think should be included in the concept map. No response as of yet! Take a minute and revisit Reading the Fire: How to Improve Your Skills and consider engaging in this project. I need your help to make this work.

Ed Hartin, MS, EFO, MIFireE, CFO

In their article Realistic Live Burn Training You Can Afford published in the May 2009 issue of Fire Engineering, Kriss Garcia and Reinhard Kauffmann extolled the advantages of constructing a panelized wood frame structure lined with several layers of 5/8″ sheetrock (see Figure 1) as an alternative to other types of structural live fire training props and facilities. I have to admit; I am intrigued by the potential advantages of this prop for demonstration of the influence of horizontal ventilation (both natural and positive pressure) and tactical training in fire attack operations. However, I am not convinced that this prop is universally superior to other types of purpose built structures used for live fire training. Choice of live fire training facilities needs to consider a range of factors including intended learning outcomes, cost (both initial and life-cycle), and environmental considerations and constraints.

Figure 1. Build and Burn Single Family Dwelling

Photo provided by Kriss Garcia (positivepressureattack.com)

Response to Garcia and Kauffmann

The most important factor to consider in design, selection, and use of live fire training props and facilities is that all live fire training is a simulation. The fire is real, but the fuel load and conditions are managed to create a specific effect (unlike in the “real world”). This does not necessarily mean that the training is ineffective, simply that each evolution is intended to provide the participants with a specific opportunity to learn and develop skills.

Having conducted a substantial number of live fire training exercises in purpose built props and acquired structures, I have found that each has its advantages. Kriss and Reinhard are particularly critical of props constructed from steel containers. They state that these type of props do not provide a realistic context for showing fire development or honing fire tactical skills. I would respectfully disagree with several caveats. 1) A single compartment prop (such as a demonstration or attack cell) is not designed or intended for tactical training. This type of prop is designed to provide a safe and effective environment to demonstrate fundamental fire development in a compartment and the opportunity for learners to practice nozzle technique. 2) Multi-compartment container-based props do provide a reasonable context for tactical training with interior doors, obstructions, potential for varied fire location, etc. However, as with all other types of prop using Class A fuel (including the build and burn structure), the fuel load and configuration is considerably different than in an actual dwelling or commercial structure. Kriss also points to the severe fire conditions and damage to both equipment and participants when working in container based props. This is the result of inappropriate use, not a defect in the type of prop used. Conditions are set and controlled by the instructors.

I have greater agreement with Kriss’s and Reinhard’s observations on high-tech gas fired props in that they often fail to replicate key fire behavior indicators and may not respond appropriately to ventilation and application of water, providing poor feedback to the learners on their performance.

I also agree with many of Kriss’s and Reinhard’s observations on acquired structures. However, their example illustrating “unpredictable fire behavior” due to medium density fiberboard that had been plastered over, resulting in ignition of pyrolysis products behind the attack crew is inaccurate. This fire behavior was entirely predictable, but unanticipated (the big difference here is that unanticipated fire behavior is simply the result of a lack of information on the part of the instructors, not by random action by the fire). Kriss states that when working with acquired structures, you need to strictly adhere to the requirements of NFPA 1403. This may be a bit misleading in that this standard applies to all live fire training (including use of the build and burn structure).

Kriss and Reinhard make a good case for the ideal live fire training structure. However, it is critical to also give some thought to the intended purpose of the building or prop. Single compartment props (regardless of what they are constructed out of) may be a tremendous tool for practicing door entry and nozzle technique much like a putting green or driving range when practicing golf. The putting green and driving range are useful tools in developing specific skills, but they are not the game of golf. The ideal live fire training prop is designed to provide a means to safely, effectively, and efficiently achieve specified learning outcomes. Much the same as there is no single tactic that will solve all problems presented on the fireground, there is no single type of live fire training prop that provides the ideal context for all types of live fire training evolutions. Again, it is critical to remember that all live fire training is a simulation. The key is to provide an adequate degree of physical and functional fidelity (look real enough and behaves real enough) to achieve the intended learning outcomes.

Intended Use and Learning Outcomes

Pilots in the United States Air Force follow an exacting course of study which includes classroom instruction, simulation, and flight instruction in trainer aircraft such as theT6 and T38 before progression to more advanced aircraft such as the F22 Raptor. Each simulator and aircraft used in this progression is intended to provide the pilot with a specific learning context. After transition to high performance aircraft, pilots continue to use simulators to practice skills that may be too high risk to perform in flight.

Figure 2. T6, T38, & F22 Aircraft

The same concept can be applied to live fire training. Observing fire development and the effect of water application may require a somewhat different context than evolutions involving door entry procedures and integration of fire control and tactical ventilation. In an ideal world, fire service agencies would have access to various types of live fire training props, each suited to providing the best context for specific levels of training and learning outcomes. Container based props and burn buildings may be simple or complex dependent on their intended purpose and learning outcomes that they are designed to support (see Figures 3-5)

Figure 3. Split Level Cell, Palm Beach County Fire Rescue

Note: This prop was constructed by Fire Training Structures, LLC and is most effective for demonstrating compartment fire behavior.

Figure 4. Large Volume Container, Swedish Civil Contingencies Agency, Sandö, Sweden

Note: This prop was constructed on site and is designed to demonstrate fire behavior and the impact of tactical operations in large compartments such as found in commercial buildings.

Figure 5. Large Masonry Burn Building, British Fire Service College

Note: This is one of many live fire training facilities at the college (including container based props and other masonry burn buildings). This building provides an industrial context for advanced firefighter training.

However, for most of us it is not a perfect world. Fire departments faced with limited fiscal resources are often limited in their options for live fire training. If they are fortunate, they have or have access to a purpose built structure that provides a safe and effective environment for a variety of types of live fire training. Each of these types of structures has limitations. The major problem encountered is when instructors and learners believe that the purpose built structure is intended to fully replicate a realistic fire environment as encountered during emergency incidents. It cannot, much the same as a flight simulator cannot fully replicate flying a high performance aircraft. However, it can replicate critical elements of context that help develop knowledge, skill, and a high level of proficiency.

Instructors must 1) identify the intended learning outcomes and critical elements of context necessary to develop learner proficiency to ensure participant safety and 2) recognize both the capabilities and limitations of the props and facilities available.

Other Considerations

Fire departments often face a more difficult challenge than determining what type of prop or facility is most effective or how to best use available facilities. The cost of live fire training is a major concern and unfortunately is often a major determining factor in the availability and type of live fire training conducted. The initial cost for purpose built props and facilities can be a large hurdle with simple commercially built props and structures costing from $40,000 to hundreds of thousands of dollars (or even more for a commercial fire simulator as illustrated in Figure 5).  However, initial cost of the prop or facility is the tip of the iceberg. Ongoing costs include fuel, maintenance, as well as instructor and student costs.

While somewhat beyond the scope of this post, environmental considerations and restrictions can also have a significant impact on both design and operation of live fire training facilities and can also have a significant impact on initial and ongoing cost.

The Way Forward

In general, there has not been a concerted and scientifically based effort to determine the critical elements of context required for live fire training. As discussed in Training Fires and Real Fires, live fire training must look real enough (physical fidelity) and react realistically to tactical operations (functional fidelity). However, we have not defined to what extent this is necessary to develop critical skills.

The variety of props, structures, and facilities available for live fire training is substantial, as is the difference in initial, ongoing, and life-cycle cost. While some work has been done comparing these various options, it is often left to individual departments to sort this out without a consistent framework or methodology.

Subsequent posts will examine these two issues in a bit more depth.

Ed Hartin, MS, EFO, MIFireE, CFO

Reference

Garcia, K. & Kaufmann, R. (2009, 2009). Realistic live-burn training you can afford. Fire Engineering, 162(5), 89-93.

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

Most of the provisions outlined in National Fire Protection Association (NFPA) 1403 Standard on Live Fire Training Evolutions, deal with mitigating the risk of traumatic injury or fatality. The standard addresses training prerequisites, but does not speak to medical and physical capacity prerequisites. The standard does specify that:

• The instructor-in-charge is responsible for provision of rest, and rehabilitation (inclusive of medical evaluation)
• Emergency medical services must be available on-site, and
• The instructor-in-charge is responsible for overall fireground activiey to ensure correct [emphasis added] levels of safety.

While the emphasis on live fire training safety has been placed on traumatic injuries and fatalities, this is not the predominant cause of live fire training line of duty deaths. Between 1994 and 2003, 65% of live fire training related fatalities resulted from physiological stress and heart attack (Grimwood, Hartin, McDonough, & Raffel, 2005)

NIOSH recently released Death in the Line of Duty Reports 2008-30 and 2008-36, both of which examined incidents in which firefighters lost their lives during or immediately after live fire training. It is easy to glance at these reports and think that this is just another heart attack with the same recommendations as all the other report. However, I encourage you to stop, read these two reports, and give some thought to what this information means to you on a personal level.

NIOSH Report 2008-30

On August 9, 2008; Captain Sean Whiten (Age 47) was leading a team of students during live fire training in a purpose built burn building. After completing an interior attack, Captain Whiten complained of being tired but otherwise had no complaints. Medical evaluation conducted as part of the rehabilitation process showed elevated pulse and blood pressure, but this was consistent with participation in a strenuous training activity.

After rehab, Captain Whiten was relaxing by his vehicle when he went into cardiac arrest. Instructors and students began CPR and applied a automatic external defibrillator prior to the arrival of an advanced life support ambulance. Paramedics initiated advanced live support procedures and transported Captain Whiten to the hospital where resuscitation efforts continued until he was pronounced dead by the attending physician.

An autopsy conducted by a forensic pathologist discovered that Captain Whiten suffered from coronary artery disease and had ventricular hypertrophy (LVH) and cardiomegaly, conditions which increase the risk of sudden cardiac death. The Captain also had mild elevation of his carboxyhemoglobin (COHb) level, but it is unclear if this had any influence on his heart attack and sudden cardiac death. The Captain’s risk factors for CAD included male gender, age over 45, high blood cholesterol, and obesity. However, he had been cleared by his primary care physician to engage in a fire department physical ability test.

NIOSH Report 2008-36

On July 6, 2008 Firefighter Rufus Brinson (Age 50) was teaching a class involving live fire training at a local community college. After several evolutions under high ambient temperature 34.4^o C (94^o F) and high relative humidity (58%), including a search drill conducted using hot smoke in a purpose built burn building, Firefighter Brinson indicated that he was not feeling well and took a break in the air conditioned cab of the engine. Another instructor took over teaching for the next evolution while Firefighter Brinson operated the pump. While refilling the apparatus tank after the final evolution, he collapsed next to the apparatus.

An instructor initiated CPR and requested an ambulance. The ambulance was staffed with intermediate level emergency medical technicians who requested response of a paramedic level unit. Transport was initiated prior to the arrival of paramedics who met the ambulance enroute to the hospital and initiated advanced life support procedures. Resuscitation efforts continued at the hospital until Firefighter Brinson was pronounced dead by the attending physician.

An autopsy conducted by the medical examiner listed congestive heart failure as the cause of death and severe coronary atherosclerotic disease and hypertensive heart disease as contributing factors. Firefighter Brinson was also found to have left ventricular hypertrophy (LVH) and cardiomegaly. Risk factors for CAD included male gender, age over 45, smoking, overweight (but not obese), and limited aerobic exercise. Firefighter Brinson had not had a medical exam by a physician in seven years.

Common NIOSH Recommendations

While both of these reports contains unique recommendations based on the circumstances involved, there are also several common recommendations:

Provide pre-placement and annual medical evaluations to fire fighters consistent with National Fire Protection As­sociation (NFPA) 1582, Standard on Comprehensive Occupational Medical Program for Fire Departments, to determine their medical ability to perform duties without presenting a significant risk to the safety and health of themselves or others.

Incorporate exercise stress tests following standard medical guidelines into a Fire Department medical evaluation program.

Ensure fire fighters are cleared for return to duty by a physician knowledge­able about the physical demands of fire fighting, the personal protective equipment used by fire fighters, and the vari­ous components of NFPA 1582.

Phase in a comprehensive wellness and fitness program for fire fighters to reduce risk factors for cardiovascular disease and improve cardiovascular capacity.

Perform an annual physical performance (physical ability) evaluation to ensure fire fighters are physically capable of performing the essential job tasks of structural fire fighting.

Provide fire fighters with medical clearance to wear a self-contained breathing apparatus (SCBA) as part of a Fire Department medical evaluation program.

These recommendations are no surprise. It is commonly known that firefighting is a physiologically stressful activity and that working in a high ambient temperature environment increases that stress substantially. Firefighters must be well and fit in order to safely and effectively operate in realistic training and on the fireground.

Responsibility

Who is responsible for ensuring that firefighters are medically and physically capable of engaging in firefighting operations? On one hand, you can make a reasonable argument that it is the fire department’s (employer’s) responsibility. One of the foundations of occupational safety and health regulation is the employer’s responsibility to provide a place of employment which is free from recognized hazards that are causing or likely to cause death or serious physical harm. However, is this solely the employer’s responsibility?

In examining this issue, I will put things in a personal context. I am a male, over 50, have a family history of heart disease, and last ago was diagnosed with hyperlipidemia (high cholesterol). While not grossly overweight, over the last 10 or 12 years my body mass index had crept up and outside the optimum. In addition, my work schedule and graduate studies had negatively impacted my workout schedule and reduced my aerobic exercise considerably. When I had my annual medical physical as a hazmat technician, the occupational medicine physician indicated that I should talk with my primary care physician about my cholesterol level lose some weight, and get more aerobic exercise. Several weeks later, I sat with my dad (a retired fire chief) as he died from congestive heart failure (at age 92). He had retired due to a heart attack the year I started my fire service career. The time that I spent with him over the last week of his life gave me a great deal to think about.

While my employer should (and does) provide medical physicals, respirator qualification, physical ability assessment, and the facilities and time to work out, I am the one responsible for action. Since last summer, I have lost 15.9 kg (35 pounds), substantially improved my aerobic fitness, and reduced my cholesterol to near optimal level. While I had not noticed the degradation in my physical capacity (other than to figure that I was getting old), I have noticed a significant improvement. I feel better on a day-to-day basis and find myself less fatigued when delivering live fire training.

Fire service organizations have a responsibility to their members to provide medical/physical assessment and wellness/fitness programs. However, each of us also has a responsibility to ensure that we are medically and physically qualified for the work we are doing. Take care of yourself and look out for the people you work with!

References

National Fire Protection Association (NFPA). (2007). Standard on live fire training evolutions. Quincy, MA: Author.

National Institute for Occupational Safety and Health (NIOSH). (2008). Death in the line of duty (Report Number 2008-30). Retrieved June 4, 2009, from http://www.cdc.gov/niosh/fire/pdfs/face200830.pdf

National Institute for Occupational Safety and Health (NIOSH). (2008). Death in the line of duty (Report Number 2008-36). Retrieved June 4, 2009, from http://www.cdc.gov/niosh/fire/pdfs/face200836.pdf

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

Art and Science of Firefighting

NIST has performed a wide range of research that can have a positive impact on the safety and effectiveness of firefighting operations. However, all too often, this information has not made it to front line firefighters. Dan Madrzykowski and Steve Kerber have made a concerted effort to address this issue and increase the day to day impact of NIST fire research. In the video overview of the wind driven fire research, Battalion Chief Jerry Tracy of the FDNY stated that this project was an effort to bridge the gap between the science and art of firefighting and get science to the street.

Research on Wind Driven Fires= Governors Island, New York City

Note: John Freeman Photo from NIST Report TN 1629

Understanding, Surviving, & Fighting Wind Driven Fires

This two DVD training package is based on NIST research conducted at the Building Fire Research Lab (BFRL) in Gaithersburg, MD and on Governors Island in New York city. The package contains:

• Written reports on the laboratory and field experiments
• Multiple videos of the experiments (from standard and thermal imaging video cameras)
• PowerPoint presentation on experimental procedures and results
• Video overview of the research and implications for fireground operations

While the reports and detailed video are tremendous resources, I believe that every firefighter in the United States would benefit from taking 86 minutes to watch the introductory video overview narrated by Battalion Chiefs Peter Van Dorpe (Chicago Fire Department), Jerry Tracy (Fire Department of New York), Dan Madrzykowski (NIST), and Steve Kerber (NIST). The overview presentation is divided into four segments:

1. Introduction and the Chicago Fire Department Experience (BC Peter Van Dorpe)
2. The FDNY Experience (BC Jerry Tracy)
3. Laboratory Experiments (Dan Madrzykowski, PE)
4. Governors Island Experiments (Steve Kerber)
5. Conclusion (BCs Peter Van Dorpe and Jerry Tracy)

This video provides a powerful explanation of the potential danger of wind driven fires (in both high and low-rise structures) and illustrates how scientific research can have a positive impact on the safety and effectiveness of fireground operations. While some may discount the information presented because the research focused (to a large extent) on high-rise buildings, many of the lessons learned have applicability to a much wider range of buildings.

In the summary section of the overview video, BC Peter Van Dorpe made several interesting observations regarding the lessons he learned from this research:

In a high-rise building, you don’t ventilate until you have water on the fire based on potential for a wind driven fire and dramatic influence of wind and ventilation on fire behavior.

Consideration of the concept that the first water on a high-rise fire [in a non-sprinklered building] should be from the exterior based on the dramatic effect of relatively low flow application from the exterior in changing conditions from severe to controllable.

BC Jerry Tracy emphasized the importance of integrating the art and science of firefighting and the need for change. Credibility is critical, both from a scientific and operational perspective. He pointed to the importance of understanding impact of changes in ventilation profile on fire behavior in all types of fires and the potential benefits of alternative strategies and tactics.

How to Order

This two DVD set can be ordered from the United States Fire Administration (USFA) Web Site. However, orders are limited to a single set per organization.

Order Evaluating Firefighting Tactics Under Wind Driven Conditions

Information on this research is also available on the NIST Wind Driven Fire Research web page.

Action Steps

Get a copy of this training package and have a look at the overview video. Ask yourself how this information can be put to work in your environment? What application does this research have beyond high-rise buildings? How can we use this information to increase the safety and effectiveness of firefighting operations in single and multi-family dwellings and in commercial buildings?

CFBT-US on Twitter

In an effort to expand our network, CFBT-US is now on Twitter! Follow Chief Instructor Ed Hartin for information on fire behavior, incident information, photos and video for B-SAHF exercises. Check out the Twitter Portal for an overview video on Twitter and additional information on this social networking tool.

CFBT-US is exploring how to integrate Twitter with the CFBT Blog (and the blog with Twitter). Please share your feedback on the effectiveness and utility of this approach to information sharing.

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.

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

This post reviews articles on positive pressure ventilation written by Watch Manager Gary West of the Lancashire (UK) Fire and Rescue Service and Battalion Chief Kriss Garcia of the Salt Lake City Fire Department. Gary, Kriss, and I were recently in Australia for a meeting of the Institution of Fire Engineers (IFE) Compartment Firefighting Special Interest Group and to present at the 2009 International Firefighting Safety Conference hosted by IFE-Australia.

Gary and Kriss are both strong advocates of positive pressure ventilation (PPV) and its use to support fire attack (positive pressure attack (PPA)). In August 2008, Gary’s article Positive Thinking was published in Fire Risk Management Journal and October 2008, Kriss’s article The Power of Negative Thinking was published in FireRescue magazine. While the titles appear to be contradictory, both of my colleagues had a common theme; the importance of education and training to ensure safe and effective tactical ventilation on the fireground.

Common Elements

Gary and Kriss both emphasize the benefits of effective use of PPV while cautioning that education in practical fluid and fire dynamics and tactical ventilation concepts must be integrated with training in PPV/PPA tactics.

Positive Thinking

Gary provides an overview of the three phased approach to PPV training and implementation commonly used in the UK. This approach is designed around building understanding of key concepts and competence in tactical skills while minimizing risk.

Phase I-Post Fire Control PPV: In this phase, PPV is limited to clearing smoke after the fire has been controlled. In many respects this is the simplest and safest application of PPV.

Phase 2-Defensive PPV: In Phase 2, PPV is used during firefighting operations to clear smoke logged areas not involved in fire. This approach requires confinement of the fire using structural barriers (e.g., closing doors) and placement of hoselines. This tactical approach is less common in the United States, likely due to differences in construction. However, use of PPV to clear and then pressurize attached exposures can be an effective tactic in limiting smoke and fire spread.

Phase 3-Offensive PPV (PPA): In the third phase, PPV precedes fire attack and has a direct influence on fire behavior as well as clearing smoke from the entry path and uninvolved areas of the building.

Gary concludes with reinforcement of the importance of education and training prior to implementation and the criticality of ongoing training and development:

It must be understood that PPV is a tool that will save the lives of casualties, and also reduce the risk to firefighters, if used correctly. Initial training should cover all aspect of fan configurations, the different phases of PPV, and include an understanding of the way in which fire behaves generally [emphasis added], among other things.

However, it cannot be emphasized enough that, if used incorrectly, PPV is a potentially life-threatening and, as such, an ongoing training and development programme ought to be available to all users [emphasis added] (P. 49).

Critique of Positive Thinking

Gary provides a solid overview of the three phased approach to PPV training and implementation used in the UK and advocates for progression to Phase 3, positive pressure ventilation in support of fire attack. However, I take exception to two statements made in this article.

The first relates to the relationship between the size of inlet and exhaust opening. “It is widely understood that the size of the exhaust(s) must add up to less than the surface are of the inlet in order that positive pressure is achieved.” This is incorrect. As outlined in my previous post, Positive Pressure Ventilation: Inadequate Exhaust, the exhaust opening should be at least equal to the size of the inlet and preferably two to three times the area of the inlet opening.

The second statement relates to water application technique. “Students have a temptation to apply water using pulsing and gas-cooling techniques. However, it is not necessary in this mode of PPV [Phase 3]. While of less concern than inadequately sized exhaust openings, use of PPV does not necessarily negate the use of gas cooling. Depending on firefighters operating location and conditions encountered, cooling hot gases may still be necessary, particularly away from the path leading from inlet to outlet. Nozzle techniques and water application should be determined based on conditions, not the ventilation tactic being used. However, that said, Gary is correct that excess steam produced during attack in the fire compartment will be carried out the exhaust opening.

Negative Thinking

Kriss shares much of Gary’s perspective regarding the value of PPV and in particular its use to support fire attack (Phase 3/PPA).  However, the main focus of The Power of Negative Thinking is on the practical aspects of the fluid dynamics involved in PPV. Kris points out that the application of positive pressure at an inlet simply adds a slight amount of pressure to direct the flow of fire effluent from the inlet to the exhaust opening(s).

Kriss states that “When PPA goes wrong, it’s usually attributable to one or two conditions, or their combination. First, mistakes result from a lack of coordination and control on the fireground including a lack of department wide training and education in the use of PPA.

Second, problems may arise from insufficient or not forward exhaust. When products of combustion are emitted under pressure adhead of the attack crews, substantial exhaust is need (P. 39).

One of the most important points that Kriss raises in this article is the importance of reading conditions at the inlet opening (which he refers to as the “ventilation” opening). “If heavy smoke and/or fire is returning to the attack entrance [and] exhausting above the blower, do not enter“ (p. 39) [additional emphasis added].

This article also outlines initial considerations for using PPV in support of fire attack Phase 3/PPA). Of particular importance is training and educating members in theory, application, and precautions involved in the offensive use of PPV. In addition, departments training and implementing the use of this tactic must define when it will be used (e.g., fire conditions, building types).

Critique of Negative Thinking

This article raises important points in developing an understanding of why PPV works (e.g., pressure differences) and provides a straightforward explanation of its safe use in support of fire attack. However, Kriss indicates that the pressure generated by the blower is less than that created by the fire and expansion of steam due to fire control operations. This is inconsistent with the results of research conducted by NIST (Kerber & Madryzkowski, 2008; 2009). On a related note, Kriss’s assumptions regarding pressure generated by steam expansion are dependent on excessive or inappropriate water application during fire suppression operations (which is not necessarily a given).

Final Thoughts

In these two articles, Gary and Kriss raise a number of important points and focus attention on the importance of understanding not simply what and how, but why. Kriss’s emphasis on the importance of having a decision-making framework and assessing conditions to determine if PPV is working prior to entry is absolutely critical. Sometime in the next couple of months I will expand on the topic of command, control, and coordination of fire control and ventilation.

Ed Hartin, MS, EFO, MIFireE, CFO

References

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

Garcia, K. (2008, October) The power of negative thinking. Fire Rescue, 38-40. Retrieved May 24, 2009 from http://positivepressureattack.com/images/pdfs/PowerOfNegativeThinking.pdf

Kerber, S. & Madrzykowski, D. (2008).Evaluating positive pressure ventilation In large structures: school pressure and fire experiments. Retrieved May 17, 2009 from http://www.fire.nist.gov/bfrlpubs/fire08/PDF/f08016.pdf.

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.

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

Burning Regime

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

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

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

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

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

Fluid Dynamics

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

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

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

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

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

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

Outlet/Inlet Ratio

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

Figure 1. PPV Efficiency Curve

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

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

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

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

Find more videos like this on firevideo.net

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

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

Next Steps

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

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

References

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

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

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