Posts Tagged ‘positive pressure ventilation’

This morning I begin the process of relocation to beautiful Whidbey Island, Washington. Later this week I begin my new job as Fire Chief with Central Whidbey Island Fire & Rescue.

Coupeville Harbor at Sunrise

As I have been packing and preparing for my move all weekend, I have not had time to develop an in-depth Monday morning post. However, I did run across an interesting video clip a few weeks ago that ties in well with our ongoing effort to develop skill in reading the fire.

R-Fire

On March 27, 2009 the Emerson and Red Oak Fire Departments were dispatched for a residential fire at 901 Lowell Ave in Emerson, IA. First arriving companies observed a fire on Floor 1 and smoke throughout the structure.

The following video clip appears to have been shot early in incident operations as positive pressure ventilation is being implemented.

Download the B-SAHF Worksheet to use as a reminder while watching the video clip.

As you view the video clip, what do the fire behavior indicators (particularly smoke and air track) tell you about the stage of fire development, burning regime, and effectiveness of tactical operations?

Questions

In addition to your general observations of B-SAHF indicators while you watched the video the first time, consider the following questions:

• Watch the video clip again and examine conditions at the inlet between 0:21 and 0:25. What does the presence of smoke (and particularly dark smoke) pushing from the inlet indicate?
• Continue the video and examine conditions between 1:02 and 1:10. What do you observe at this point? What do smoke and air track conditions indicate now?
• Continue on and examine conditions closely between 2:28 and 2:48. What does the variation in smoke and air track indicators at different points on the exterior of the structure tell you?

Back on Schedule!

I plan to be back on track with the next post in the series examining nozzle techniques on Thursday, November 12. I have been having an e-mail conversation BC Mike Walker of the Oklahoma City Fire Department regarding nozzle techniques and flashover. Mike is working on a research project regarding “right for reach and left for life”. Interestingly, when I received Mike’s first e-mail, I was in the process of outlining an upcoming blog post on the concept of “Battle Drills” to deal with or escape from conditions such as those resulting from unplanned changes in ventilation (window failure, wind, etc.).

Ed Hartin, MS, EFO, MIFireE, CFO

Building Factors, Smoke, Air Track, Heat, and Flame (B-SAHF) are critical fire behavior indicators. Understanding the indicators is important, but more important is the ability to integrate these factors in the process of reading the fire as part of size-up and dynamic risk assessment.

This post reviews application of the B-SAHF organizing scheme to recognizing and identifying stages of fire development and burning regime.

Compartment Fire Development

Part of the process of reading the fire involves recognizing the stages of fire development and burning regime (e.g., fuel or ventilation controlled). Remember that fire conditions can vary considerably throughout the building with one compartment containing a fully developed fire, an adjacent compartment in the growth stage, and still other compartments yet uninvolved. Similarly, burning regime may vary from compartment to compartment. Recognizing the stages of fire development and burning regime allows firefighters to predict what is likely to happen next (if action is not taken), potential changes due to unplanned ventilation (such as failure of a window), and the likely effect of tactical action.

Compartment fire development can be described as being comprised of four stages: incipient, growth, fully developed and decay (see Figure 1). Flashover is not a stage of development, but simply a rapid transition between the growth and fully developed stages.

Figure 1. Heat Release Rate (HRR) and Fire Development

Compartment fires do not always follow the simple, idealized fire development curve illustrated in Figure 1. The speed with which the fire develops, peak heat release rate, and duration of burning are dependent on both the characteristics of the fuel involved and ventilation profile (available oxygen).

Hazard of Ventilation Controlled Fires

Many if not most fires that have progressed beyond the incipient stage when the fire department arrives are ventilation controlled. This means that the heat release rate (the fire’s power) is limited by the ventilation profile, in particular, the existing openings.

If ventilation is increased, either through tactical action or unplanned ventilation resulting from effects of the fire (e.g., failure of a window) or human action (e.g., exiting civilians leaving a door open), heat release rate will increase, potentially resulting in a ventilation induced flashover as illustrated in Figure 2.

Figure 2. Ventilation Induced Flashover

Incipient Stage

Going back to the basics of fire behavior, ignition requires heat, fuel, and oxygen. Once combustion begins, development of an incipient fire is largely dependent on the characteristics and configuration of the fuel involved (fuel controlled fire). Air in the compartment provides adequate oxygen to continue fire development. During this initial phase of fire development, radiant heat warms adjacent fuel and continues the process of pyrolysis. A plume of hot gases and flame rises from the fire and mixes with the cooler air within the room. This transfer of energy begins to increase the overall temperature in the room. As this plume reaches the ceiling, hot gases begin to spread horizontally across the ceiling. Transition beyond the incipient stage is difficult to define in precise terms. However, as flames near the ceiling, the layer of hot gases becomes more clearly defined and increase in volume, the fire has moved beyond its incipient phase and (given adequate oxygen) will continue to grow more quickly.

Depending on the size of the compartment and ventilation profile, there may only be a limited indication (or no indication at all) from the exterior of the building that an incipient stage fire is burning within. Incipient stage indicators are listed in Figure 3

Figure 3. B-SAHF Indicators of an Incipient Stage Fire

Application Exercise

Consider the following situation and how critical fire behavior indicators would present. Use the B-SAHF model to help you frame your answers.

You have responded to a fire in a one-story single family dwelling of wood frame construction. An incipient fire is burning in a bedroom on the Alpha Bravo corner of the structure. The fire is limited to a plastic trash can containing waste paper which is located next to the bed.

• What conditions would you expect to see from the exterior of the structure?
• What indicators may be visible from the front door as you make entry?
• What might you observe traveling through the living room and down the hallway?
• What conditions would you find in the bedroom?

It is essential to think about what you are likely to find inside when observing fire behavior indicators from the exterior and performing a risk assessment. After making entry, consider if conditions are different than you anticipated.

• Why might this be the case?
• What differences in conditions would be cause for concern?

More to Follow

The next post in this series will continue examination of the relationship between the B-SAHF indicators, fire development, and burning regime with a look at growth stage fires in both fuel and ventilation controlled burning regimes.

Ed Hartin, MS, EFO, MIFireE, CFO

This post 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.

Effective use of positive pressure ventilation aids in fire control and provides increased tenability throughout the fire building. However, inappropriate or ineffective use of this tactic has resulted in numerous near misses, injuries, and more than a few line of duty deaths. In many of these cases, positive pressure was applied with an inadequate exhaust opening.

Find more videos like this on firevideo.net

Did you ever wonder why the size and location of the exhaust opening is critical to safe and effective use of positive pressure ventilation? If not, maybe you should!

A Quick Review

As discussed in an earlier post (see Language and Understanding: Extreme Fire Behavior), common language and definitions are critical to developing a shared understanding. To that end, I want to start this examination of positive pressure ventilation (PPV) with a brief review of terminology used in this post.

Ventilation: The exchange of the atmosphere inside a compartment with the atmosphere outside the compartment. Ventilation is ongoing in all habitable spaces. Under fire conditions, this involves exit of smoke and intake of fresh air (if smoke is visible, ventilation is occurring).

Tactical Ventilation: Planned, systematic, and coordinated removal of heat, smoke, and fire gases (fire effluent) and their replacement with fresh air. There are three important parts of this definition, 1) tactical ventilation is part of the overall tactical plan and is coordinated with other fireground operations (particularly fire control), 2) hot fire effluent is removed, and 3) fresh (cooler) air is introduced into the compartment.

Note: I gave a bit of thought to use of the terms smoke and fire effluent in this discussion of ventilation. The International Standards Organization (ISO) definition of smoke focuses on the visible products of combustion while fire effluent includes all gaseous, aerosol, and particulates generated by combustion. The National Fire Protection Association (NFPA) definition of smoke is comparable to the ISO definition of fire effluent. Given that the traditional definition of (tactical) ventilation refers to “heat, smoke, and fire gases” (IFSTA, 2008, p. 541), I will use the term fire effluent as the broader, more encompassing term (inclusive of smoke and fire gases).

Natural Ventilation: Use of pressure and density differences generated by the higher temperature of gases inside the compartment than outside and ambient wind conditions to accomplish the exchange of hot fire effluent and air.

Assisted Ventilation: These tactics use mechanical or hydraulically generated pressure to influence and increase the exchange of fire effluent and air. Assisted ventilation includes the use of fog streams and fans to reduce pressure at the exhaust opening (negative pressure ventilation) and use of fans or blowers to increase pressure at the inlet opening (positive pressure ventilation).

Positive Pressure Ventilation (PPV): Use of a blower at the inlet opening to increase the pressure differential between the inlet and exhaust opening to control and increase the exchange of fire effluent and air.

Positive Pressure Attack (PPA): This term was coined by Garcia, Kauffmann, & Schelble (2006) to differentiate positive pressure ventilation initiated prior to fire attack from use of this tactic following fire control operations. From a physics perspective, PPV and PPA are the same, the term PPA simply designates the sequence in which the tactic is performed.

Exhaust Opening: The opening(s) used for removal of fire effluent. Note that this opening may be created by unplanned ventilation due to fire effects, civilians, or freelancing responders or it may be created as the result of tactical action. Remember that any location where flames and/or smoke is visible is an exhaust opening.

Inlet Opening: The opening(s) used to introduce fresh air into the compartment. As with exhaust openings, inlet openings may be unplanned or planned. Openings may serve simply as an inlet or may serve as both an inlet and outlet with fire effluent exiting at the top and air entering at the bottom (bi-directional air track).

Smoke Movement in Buildings

Fluids (like fire effluent) flow from areas of higher pressure to areas of lower pressure. In a compartment fire, energy released by combustion raises the temperature of the fire effluent and entrained air. As temperature increases, gases expand and become less dense (more buoyant). However, when gases are confined, increased temperature results in increased pressure. These differences in density and pressure result in movement of smoke out of the compartment and inward movement of air from outside the compartment. This exchange may be through normal building leakage, unplanned ventilation, or tactical ventilation.

The pressure generated by a fire inside a compartment is dependent on the heat release rate, ventilation (openings), and resulting temperature inside the compartment. However, NFPA 92A Standard for Smoke-Control Systems Utilizing Barriers and Pressure Differences (NFPA, 2006) specifies pressure differences in non-sprinklered buildings of between 12.5 Pascal (Pa) and 44.8 Pa to overcome the pressure resulting from hot gases at a temperature of 927^o C (1700^o F) next to the smoke barrier (these pressures include a 7.4 Pa safety factor). If the safety factor is removed, the pressure generated by a fire in a non-sprinklered occupancy would likely be between 5 Pa and 37.3 Pa. All very interesting, but what is a Pascal?

While firefighters in the United States are generally familiar with pounds per square inch (psi) as a unit of measure for pressure, the standard international unit for pressure is the Pascal (P). A Pascal is an extremely small unit (1 psi = 6895 Pa) roughly equivalent to the pressure exerted by a sheet of writing paper laying on a flat surface. As you can see, the pressure generated by the fire is quite small, but more than adequate to result in significant movement of fire effluent!

Two key points that influence movement of fire effluent and ventilation under fire conditions:

• If the temperature of fire effluent is higher than that of the ambient air it will tend to rise.
• Fire effluent flows from areas of higher pressure to areas of lower pressure.

PPV Basic Concepts

Many firefighters think that they understand positive pressure ventilation and how it should (and should not) be used on the fireground. Some do. However, there are a number of common misconceptions and a great deal of misunderstanding when it comes to effective application of this tactic.

A good starting point is to examine the fundamental purpose of the use of positive pressure in tactical ventilation and anti-ventilation. “The purpose of the positive pressure ventilation fan is to create pressures higher than that of the fire to manage where the smoke and hot gases flow” (Kerber & Madrzykowski, 2008). When used in tactical ventilation, positive pressure can be used to control air track and speed the removal of fire effluent from the compartment. In anti-ventilation (e.g., pressurization of a stairwell or attached exposure), positive pressure is used to confine the fire effluent.

The basic sequence of positive pressure tactical ventilation is as follows

1. Size-up and dynamic risk assessment (ongoing)
2. Determination that positive pressure is indicated (and not contraindicated)
3. Identification of appropriate and adequate exhaust openings
4. If necessary creating or enlarging exhaust openings
5. Application of positive pressure at the inlet
6. Verification that positive pressure ventilation is working

Positive pressure ventilation is an extremely powerful tool that can rapidly clear smoke logged areas of the building. However, if used without thinking and understanding the influence of ventilation on fire behavior, it can cause extreme fire behavior even more quickly. The following criteria should be met for safe and effective use of positive pressure ventilation:

• Firefighters understand the use of PPV and are skilled in its use
• The required tools are available
• Location and extent of the fire is known Svensson, 2000). This is not an absolute requirement, but influences the most appropriate location for the exhaust opening)
• A charged hoseline is in place for fire control (Svensson, 2000)
• Backdraft conditions are not present (Svensson, 2000; Garcia, Kauffmann, & Schelble, 2006).
• Victims or firefighters are not between the fire and the exhaust opening (Svensson, 2000)
• Victims or firefighters are not in the exhaust opening (Garcia, Kauffmann, & Schelble, 2006)
• Ventilation openings can be controlled and an adequate exhaust (preferably 2 to 3 times the size of the inlet) opening is provided (Svensson, 2000).
• Positive control of the blower (the ability to start and stop positive pressure immediately)
• Ventilation is coordinated with fire attack (Svensson, 2000; Garcia, Kauffmann, & Schelble, 2006). This requires communication with personnel at the outlet, inlet, interior working positions, and Command.

Common Problems

Kriss Garcia, co-author of Positive Pressure attack for ventilation & firefighting indicates that most situations where use of positive pressure ventilation resulted in occurrence of extreme fire behavior or some other adverse outcome generally involve one or more of the following (personal communication, May 2006):

• Lack of an exhaust opening
• Inadequate exhaust opening size
• Lack of command, control, & coordination

More to Follow

My next post will get to into the nuts and bolts of exhaust opening size and why use of positive pressure with an inadequate exhaust opening can result in extreme fire behavior.

References

Garcia, K., Kauffmann, R. & Schelble, R. (2006). Positive pressure attack for ventilation & firefighting. Tulsa, OK: Penwell.

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

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.

National Fire Protection Association (NFPA). (2006). NFPA 92A. Standard for smoke-control systems utilizing barriers and pressure differences. Quincy, MA: Author.

My last two posts (Contra Costa County Line of Duty Deaths (LODD) Part 1 & Part 2) examined the conditions and circumstances involved in the incident that took the lives of Captain Matthew Burton and Engineer Scott Desmond while conducting primary search in a small residential structure in San Pablo, California early on the morning of July 21, 2007.

As identified in the Contra Costa County Investigation and NIOSH Death in the Line of Duty Report F2007-28, these line of duty deaths were the result of a complex web of events, circumstances, and actions.

These two reports identify the rapid fire progression that trapped Captain Burton and Engineer Desmond as a fire gas ignition (county and NIOSH reports) or ventilation induced flashover (NIOSH report). Both reports also point to ineffective or inappropriate use of positive pressure ventilation as a contributing factor in the occurrence of extreme fire behavior. However, neither report provides a substantive explanation of how and why this extreme fire behavior occurred.

Investigative Approach

Developing a reasonable explanation of the extreme fire behavior that occurred in this incident involved application of the scientific method as outlined in NFPA 921 Standard on Fire and Explosion Investigations (2008).

The following analysis is based on narrative data and photographic evidence provided in the Contra Costa County Fire Protection District Investigation Report: Michele Drive Line of Duty Deaths and the video taken by the Q76 Firefighter.

In that the district and NIOSH had already collected data, this effort focused on 1) analysis of the data contained in the incident reports, photographs, and video; 2) development of a hypothesis that provided an explanation for what occurred (deductive reasoning), 3) testing this hypothesis (inductive reasoning); 4) revising the hypothesis as necessary; and 5) selecting a final hypothesis.

Figure 1. Fire Development in Bedroom 2

Hypothesis

The fire originated in Bedroom 2, likely on or near the bed. In the growth stage, the fire extended through the hallway into the living room (see Figure 1). The fuel load in the living room and ventilation provided by the open front door permitted the fire to progress through flashover and become fully developed (see Figure 2).

Figure 2. Extension and Fire Development in the Living Room

The extent of fire in the living room consumed the oxygen supplied through the front door, resulting in an extremely ventilation controlled fire in the hallway and bedroom. Unburned flammable products of combustion and pyrolysis products from contents and structural materials accumulated in the upper layer in the bedrooms and hallway.

Figure 3. Fire Control and Development of a Gravity Current

Extinguishment of the fire in the living room allowed development of a gravity current and movement of oxygen through the living room to the hallway and bedrooms allowing flaming combustion in these areas to resume.

Figure 4. Positive Pressure Ventilation

Flaming combustion in the hallway or bedroom resulted in piloted ignition of a substantive accumulation of pyrolysis products and flammable products of incomplete combustion in the upper layer within the hallway and bedrooms. Application of positive pressure at the door on Side A influenced (or speeded up) this phenomena and may have increased the violence of this ignition (due to increased pressure and confinement) but likely aided in limiting the spread of flaming combustion from the hallway into the living room.

Figure 5. Fire Gas Ignition

Supporting Information

Information supporting the preceding hypothesis is divided into three categories: Known, suspected, and assumptions.

Known

The cause and origin  and line of duty death investigation conducted by the Contra Costa Fire Protection District and line of duty death investigation conducted by NIOSH identified and documented a range of data supporting this hypothesis. These data elements include physical evidence, and narrative data obtained from interviews with individuals involved in the incident.

• The fuel load in the bedroom included a bed, dresser, and other contents, exposed wood ceiling, carpet, and carpet pad.
• Fire originated in Bedroom 2 (on or near the bed)
• The female occupant exited the structure prior to making a 911 call to report the fire (via cell phone).
• The female occupant then reentered the building prior to the arrival of the first fire unit in an effort to rescue her husband. [Observations by bystanders included in the report]
• The fire in Bedroom 2 entered the growth stage and extended into the hallway and subsequently the living room. This fire spread was in part due to the combustible wood ceiling. [Information on the cause and origin investigation provided in the report]
• Windows other than the living room window on Side A were substantively intact until the occurrence of the extreme fire behavior event. [Observation by firefighters included in the report]
• E70 knocked down the fire in the living room prior to initiating primary search (without a hoseline). E70 used a left hand search pattern in which they would have moved into the hallway and bedrooms located on Side B of the residence.
• A blower was placed at the front door while E70 and E73 were conducting primary search. Due to the placement of the blower close to the door, it is possible that the air cone did not fully cover the door opening. There is no mention in the report regarding the air track at the door or living room window following placement of the blower. However, E73 reported increased visibility and temperature in the kitchen a short time after the blower was placed, and observed rollover from the hallway leading to the bedrooms.]
• The large window in the living room (if fully cleared of glass) would provide approximately equal area as the door on Side A used as an inlet. Given an equal sized inlet and outlet, efficiency of PPV is likely to be approximately 70%. However, given the location of the exhaust opening next to the inlet, the effectiveness of this ventilation at clearing smoke from compartments beyond the living room and kitchen would have been limited.
• Vertical ventilation was not completed until after the occurrence of the extreme fire behavior phenomena that trapped and killed Captain Burton and Engineer Desmond. The exhaust opening created in the roof had limited impact on interior conditions when it was completed due to the presence of the original roof.
• Fuel load in this compartment was more than sufficient to provide the heat release rate necessary to allow fire development to flashover. [This assessment is based on post-fire photos, room dimensions, and ventilation openings at the time of the ignition].
• Other bedrooms contained a similar fuel load.

Deductions

Several factors supporting the stated hypothesis are not directly supported by physical evidence or narrative data. These elements are deduced based on the design, construction, and configuration of the building and principles of fire dynamics in conjunction with known information.

• The front door remained open after the female occupant reentered. [E70 reported fire and smoke showing from the door and living room window on arrival, but no information provided in the report regarding the position of the door or extent to which the window had failed (fully or partially)]
• Use of the blower is likely to have increased mixing of air and hot, fuel rich fire gases in the hallway, particularly near the opening between the hallway and the living room. Ventilation of smoke from the living room and kitchen through the window on Side A, likely reduced the potential for flaming combustion to have extended from the hallway into the living room.
• Heat conducted through the tongue and groove wood roof/ceiling may have resulted in melting and gasification of asphalt roofing which may have been forced through gaps between the planks to add to the gas phase fuel resulting from pyrolysis and incomplete combustion of contents and structural surfaces within the involved compartments.
• The primary source of air for the fire was through the front door and the living room window. The bottom of the doorway was the lowest opening in the building, likely resulting in a bi-directional air track with smoke exiting out the top of the door and air entering at the bottom. While the sill of the living room window was higher than the door, a bi-directional air track likely developed at this opening as well, with the extreme lower portion of the window opening serving as an inlet while the top of the window functioned as an outlet for flames and smoke [No information about air track at the front door was provided in the report.]
• The fire in the living room reached the fully developed stage after the civilian occupant reentered and prior to the arrival of E70 [This deduction is based on the ability of the female occupant to enter and make her way to the kitchen and the presence of flames exiting the door and living room window on Side A when E70 arrived]

Assumptions

In addition to known and deduced information, the hypothesis is based on the following assumptions.

• The fully developed, ventilation controlled fire in the living room substantively utilized the atmospheric oxygen provided by the air entering through the front door, causing the fire in Bedroom 2 and the hallway to enter ventilation controlled decay. The decay stage fire and heat from the hot gas layer present in the hallway and adjacent rooms continued pyrolysis of fuel packages in this area, resulting in accumulation of a substantial concentration of gas phase fuel in the smoke.
• Control of the fully developed fire in the living room reduced oxygen demand from the fire. The bi-directional air track would have continued and gravity current would have increased air supply to the ventilation controlled decay stage fire in the hallway and bedroom(s).
• Establishment of positive pressure ventilation with the door on Side A serving as the inlet (or inlet and outlet) and the living room window serving as an outlet would have cleared smoke from the living room, but would not have influenced smoke movement from the hallway and bedrooms (as quickly).

Validation

Special thanks to Dr. Stefan Svensson of the Swedish Civil Contingencies Agency and Assistant Professor Greg Gorbett of Eastern Kentucky University for serving as critical friends and providing useful feedback in development of this analysis.

This hypothesis is supported by a range of evidence, deductions and assumptions. However, further validation would require use of other methods such as development of a computational fluid dynamics model and small or full scale fire tests.

More to Follow

My next post will examine the potential influence of positive pressure ventilation (PPV) in this incident as well as a broader look at potential hazards when PPV is used incorrectly or under inappropriate circumstances.

Ed Hartin, MS, EFO, MIFireE, CFO

References

Contra Costa County Fire Protection District.  (2008). Investigation report: Michele drive line of duty deaths. Retrieved February 13, 2009 from http://www.cccfpd.org/press/documents/MICHELE%20LODD%20REPORT%207.17.08.pdf

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

National Fire Protection Association (NFPA) (2008) NFPA 821 Standard on fire and Explosion Investigations. Quincy, MA: Author.

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

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

Firefighting Operations

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

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

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

Figure 1. Floor Plan-149 Michelle Drive

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

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

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

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

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

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

Figure 2. Extreme Fire Behavior

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

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

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

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

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

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

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

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

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

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

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

Figure 4. Hallway Ceiling.

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

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

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

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

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

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

Firefighter Rescue Operations

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

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

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

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

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

Timeline

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

Questions

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

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

Ed Hartin, MS, EFO, MIFireE, CFO

References

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

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

As discussed in previous posts, developing mastery of the craft of firefighting requires experience. However, it is unlikely that we will develop the base of knowledge required simply by responding to incidents. Case studies provide an effective means to build our knowledge base using incidents experienced by others.

Introduction

The deaths of Captain Matthew Burton and Engineer Scott Desmond in a residential fire were the result of a complex web of circumstances, actions, and events. This case study was developed using the Contra Costa County Fire Protection District Investigative Report and NIOSH Death in the Line of Duty Report 2007-28 and video taken by a Firefighter assigned to Quint 76 (Q76), the first alarm truck company. This case study focuses on the fire behavior and related tactical operations involved in this incident. However, there are a number of other lessons that may be learned from this incident and readers are encouraged to review both the fire district’s investigation and NIOSH report for additional information.

The Case

Early on the morning of July 21, 2007, Captain Matthew Burton and Engineer Scott Desmond were performing primary search of a single family dwelling in San Pablo, California. During their search, they were trapped by rapidly deteriorating conditions and died as a result of thermal injuries and smoke inhalation. Two civilian occupants also perished in the fire.

Figure 1. 149 Michele Drive-Alpha/Delta Corner

Note: Contra Costa Fire Protection District (Firefighter Q76) Photo, Investigation Report: Michele Drive Line of Duty Deaths. This photo illustrates conditions shortly after 0159 (Q76 time of arrival).

Building Information

The fire occurred in a 1,224 ft² (113.7 M2), one-story, wood frame dwelling with an attached garage at 149 Michele Drive in San Pablo (Contra Costa County), California. The house was originally built in 1953 and remodeled in 1991 with the addition of a pitched rain roof over the original (flat) roof.

This single story structure was of Type V, platform frame construction. The building was originally constructed with 4″ x 8″ (102 mm x 203 mm) beams supporting a flat roof with 2″ x 6″ (51 mm x 152 mm) tongue and groove planking with a built-up overlay consisting of several layers of tar and gravel. The pitched roof was constructed of 2″ x 8″ (51 mm x 203 mm) rafters covered with plywood and asphalt composite shingles. The ridge of the pitched roof was parallel to Side A. The gable ends on Sides B and D were constructed of plywood and fitted with a small gable vent.

Figure 2. Floor Plan-149 Michelle Drive

Note: This floor plan is based on data provided in the Contra Costa Fire Protection District Investigation Report and is not drawn to scale. The position of exterior doors and condition of windows as illustrated is based on the narrative or photographic evidence. Interior doors are shown as open as illustrated in the report. Fire service casualties are designated as follows: 1) Captain Burton, 2) Engineer Desmond.

All windows with the exception of the Living Room and Bedroom 1 (see Figure 2) were fitted with security bars (see Figure 3). The front door was the primary exit. In addition, an additional exit was provided from the kitchen through the garage to the exterior on Side D. The exterior door on Side D was fitted with a security grate.

Figure 3. View of Side C from the B/C Corner

Figure 4. Hallway and Bedroom 2

Note: Figures 3 & 4 adapted from Contra Costa Fire Protection District Photos (brightness and contrast adjusted to provide increased clarity).

Interior walls were gypsum board with wood veneer paneling on some of the walls (e.g., living room). All ceilings with the exception of the kitchen were exposed 2″ x 6″ (51 mm x 152 mm) tongue and groove planking (see Figure 4). The kitchen ceiling was covered with gypsum board. Ceiling height was 8′ (2.4 M).

Figure 5. Living Room

Note: Adapted from Contra Costa Fire Protection District Photos, Investigation Report: Michele Drive Line of Duty Deaths.

The Fire

Investigators determined that the fire likely originated on or near the east end of the bed in Bedroom 2 (see Figures 2 & 3). The likely source of ignition was improper discard of smoking materials. Developing into growth stage, the fire progressed from Bedroom 2 into the hallway (see Figures 2 & 4) leading to the living room, dining area, and kitchen (see Figures 2 & 5). It is likely that the door on Side A was closed at the time of ignition, but was opened by an occupant exiting some time after discovery of the fire.

Dispatch Information

Occupants discovered the fire and notified a private alarm company via two-way intercom at 0134. The alarm company notified the Contra Costa Regional Fire Communications Center of receipt of a fire alarm from 149 Michelle Drive at 0136 using the non-emergency telephone number. The alarm company did not indicate that they had talked to the resident who had reported a fire, but simply that they had received a fire alarm. The caller was placed on hold due to a higher priority 911 call. The dispatcher returned to the call from the alarm company at 0142 to obtain the address and callback information. Two attempts were made to call the incident location prior to dispatch of Engine 70 at 0144 to investigate the alarm. Contra Costa County Fire Protection District (CCCFPD) Engine 70 responded at 0145.

Shortly after Engine 70 responded, the communications center received a cell phone call from the female occupant at 149 Michelle Drive. This call was originally received by the California Highway Patrol and transferred to Contra Costa County Regional Fire Communications Center. The caller reported a residential fire and indicated that she had not been able to get her husband out of the building. Between the time that she spoke to the dispatcher and arrival of Engine 70, the female occupant reentered the building to attempt to rescue her husband (leaving the door on Side A open).

At 0146, the dispatcher upgraded the response to a residential fire and added two additional engines, a quint (as the truck company), and a battalion chief. Subsequent to the upgrade to a residential fire, additional 911 calls were received reporting a residential fire at 149 Michelle Drive.

Resources dispatched on the first alarm were as follows: Engine 70 (already responding on the initial dispatch for a residential alarm), Engine 69 (CCCFPD) as well as Rodeo-Hercules Fire Protection District Quint 76, and Battalion 7.  Richmond Fire Department Engine 68 was requested for automatic aid response through the Richmond Communications Center to fill out the first alarm assignment. Pinole Fire Department Engine 73 cleared a medical call a short distance away from the incident location and added themselves to the first alarm assignment. With the addition of Engine 73, the dispatcher canceled response of Engine 68 through Richmond Dispatch.

Note: Engine 73 was using an apparatus normally assigned at Station 74 which was marked with the designation Engine 74. This created some confusion during initial incident operations.

Weather Conditions

Conditions were clear, temperature was approximately 61^o F (16^o C), with a south to southeast (Side D to Side B) wind at between 2 and 6 mph (3.2 and 9.7 kph).

Conditions on Arrival

Shortly prior to arrival, Engine 70 reported “smoke showing a block out” and was advised by the dispatcher that the female occupant had been trying to get her husband out of the house and that it was uncertain if she had been successful. Engine 70 arrived at 0150, reported heavy smoke and fire from a single-story residential structure (flames and smoke were exiting from the open front door and large living room window on Side A), and established Command. Due to delays in the dispatch process, the time from the initial auomatic alarm until the arrival of E70 was approximately 16 minutes.(Refer to Contra Costa Fire Protection District, Investigation Report: Michele Drive Line of Duty Deaths for additional information regarding factors influencing the dispatch delay.

Questions

The following questions provide a basis for examining the first segment of this case study. You have an advantage that Captain Burton did not in that you are provided with a floor plan, photographs of Side C and the interior, and have knowledge of the eventual outcome. However, it is important that you place yourself in the situation encountered on arrival.

1. What stage(s) of fire and burning regime(s) were present in the building when E70 arrived? Consider potential differences in conditions in the living room, hallway, and bedrooms?
2. If you suspect that fire conditions in the living room were different than the hallway and bedrooms, why might this be the case? What evidence supports your position? What are your assumptions?
3. While limited information is available about the fire behavior indicators present during this incident, what Building, Smoke, Air Track, Heat, and Flame (B-SAHF) indictors did E70 observe when they arrived?
4. What B-SAHF indicators would you anticipate could have been observed on Sides B and C had this reconnaissance been conducted prior to making entry?
5. If you were faced with this situation, fire showing from the front door and window of a single family dwelling with persons reported, what actions would you take?
6. How do you think your selection of tactics would have influenced fire behavior and interior conditions?

Tactical Operations & Fire Behavior

My next post will examine tactical operations conducted by the first arriving companies and fire behavior encountered inside the building.

Ed Hartin, MS, EFO, MIFireE, CFO

References

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

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

The deaths of Captain Matthew Burton and Engineer Scott Desmond in a residential fire on July 27, 2001 were the result of a complex web of circumstances, actions, and events. The Contra Costa County Fire Protection District and National Institute for Occupational Safety and Health (NIOSH) both investigated this incident and have published reports that outline the sequence of events, contributing factors, lessons learned, and recommendations. Readers are encouraged to read the Contra Costa County Fire Protection District Report and National Institute for Occupational Safety and Health (NIOSH) Death in the Line of Duty Report F2007-28. Also have a look at Tim Sendelbach’s post In Their Honor at Firefighter Nation.

Incident Overview

Early on the morning of July 21, 2007, Captain Matthew Burton and Engineer Scott Desmond were performing primary search of a small, one-story, single family dwelling in San Pablo, California. During their search, they were trapped by rapidly deteriorating conditions and died as a result of thermal injuries and smoke inhalation. Two civilian occupants also perished in the fire.

The crews of the first arriving companies (two engines arrived almost simultaneously) faced significant challenges with a report of civilian occupants trapped in the building, flames from the door and a large window on Side Alpha and smoke throughout the structure. The two engines rapidly initiated fire attack, primary search, and placed a blower for positive pressure ventilation. During interior firefighting operations, Captain Burton and Engineer Desmond were trapped extremely rapid fire development in the hallway and bedrooms while conducting search without a hoseline.

Contributing Factors

NIOSH Report F2007-28 identifies eight factors that contributed to the tragic outcome of this incident.

• Failure by the alarm company to report a confirmed fire
• Inadequate staffing to effectively and safely respond to a structure fire
• The failure to conduct a size-up and transfer incident command
• Conducting a search without protection from a hoseline
• Failure to deploy a back-up hoseline
• Improper/inadequate ventilation
• Lack of comprehensive training on fire behavior
• Failure to initiate/deploy a Rapid Intervention Crew

NIOSH identified these factors as contributing, not causal factors. This reflects the complex and interrelated relationship between the factors that resulted in the occurrence of extreme fire behavior during primary search operations and inability of the search crew to escape from the building.

As you read the reports on this incident consider the contributing factors identified by NIOSH. Do you agree that these factors were contributory; if so, in what way; if not, why not?

NIOSH Recommendations

Based on analysis of this incident and the contributing factors, NIOSH made nine recommendations [emphasis added]:

• Ensure that fire and emergency alarm notification is enhanced to prevent delays in the alarm and response of emergency units
• Ensure that adequate numbers of staff are available to immediately respond to emergency incidents
• Ensure that interior search crews are protected by a staffed hose line
• Ensure that firefighters understand the influence of positive pressure ventilation on fire behavior and can effectively apply ventilation tactics
• Develop and implement standard operating procedures (S.O.P.’s) regarding the use of backup hose lines to protect the primary attack crew from the hazards of deteriorating fire conditions
• Develop and implement (S.O.P.’s) to ensure that incident command is properly established, transferred and maintained
• Ensure that a Rapid Intervention Crew is established to respond to fire fighters in emergency situations
• Implement joint training on response protocols with mutual aid departments

Additionally standard setting agencies, states, municipalities, and authorities having jurisdiction should:

• Consider developing more comprehensive training requirements for fire behavior to be required in NFPA 1001 Standard for Fire Fighter Professional Qualifications and NFPA102 1 Standard for Fire Officer Professional Qualifications and states, municipalities, and authorities having jurisdiction should ensure that fire fighters within their district are trained to these requirements

This final recommendation is extremely significant in that this is the first time that NIOSH has indicated that lack of effective fire behavior training in the US fire service is a systems problem. Fire training is often driven by the need to meet (rather than exceed) minimum standards. This is understandable, given the wide range of competencies required of today’s firefighters and fire officers. However, the need to develop a sound understanding of fire behavior and practical fire dynamics is critical. While this issue needs to be addressed in the professional qualification standards, we should not wait until this is accomplished. Firefighters and fire officers must become (or continue to be) students of fire behavior and develop proficiency in reading the fire and mitigation of the hazards presented by extreme fire behavior phenomena such as flashover, backdraft, smoke explosion, and flash fire.

Ed Hartin, MS, EFO, MIFireE, CFO

Second only to the great solid stream versus fog debate, ventilation strategies seem to create the most discussion and disagreement among fire service practitioners. Vertical or horizontal; natural, negative, or positive pressure; vent before, during or after fire control? These are all good questions (many of which have more than one answer).

The Importance of Why

BC Kriss Garcia recently published an interesting article titled Education vs. Training in Fire Space Control (Fire Engineering, September 2008) examining the difference between training and education, in particular as it relates to ventilation strategies. Kriss emphasized that we train to improve performance and efficiency, but use education to develop our ability to think and understand not only how, but when, why, and why not. Both are critical to today’s firefighters and fire officers.

Space Control

Firefighters sometimes perform ventilation operations by routine, executing tactics simply based on common practice without thought to the influence of these actions on the fire environment and fire behavior. Kriss emphasizes the importance of understanding the effect of changing the ventilation profile and its relationship to fire control, stating:

Absolute control of the space you are opening is necessary for a safe and effective fire attack. If firefighters cannot control the space with enough direct application of [British thermal unit] Btu -quenching water, they should not be opening the space, encouraging additional free burning.

The concepts included in this brief statement are critical, but could be expanded and clarified a bit.

• Developing and maintaining control of the space is critical to offensive firefighting operations and the survival of civilian fire victims who may be trapped in the building.
• Increasing the air supply to a ventilation controlled fire will increase the heat release rate. Heat release rate is measured in kilowatts (kW) or British thermal units (Btu)/m.
• Water application in liters or gallons per minute (lpm or gpm) must exceed the critical rate of flow based on the heat release rate (kW or Btu/min) developed by the fire.

There are two key differences in this expanded outline of the importance of understanding the influence of changing the ventilation profile: 1) Recognizing and understanding the dominant influence on current fire development, fuel or ventilation. Heat release rate from a fire burning in the ventilation controlled burning regime will increase if the fire receives additional air. 2) Water application (lpm or gpm) must be sufficient to overcome the heat release rate from the fire. While it is common to hear firefighters say that gpm must overcome Btu, this is not completely correct. Btu is a measure of energy much the same as liters or gallons is a measure of the volume of water. Kilowatts (1000 joules/second) or Btu/minute are a measure of heat release rate as lpm or gpm are a measure of water application rate.

Tactical ventilation is the other element of space control. Smoke contains unburned pyrolizate and flammable products of incomplete combustion, and as such is fuel. Hot fuel gases overhead can be cooled, providing a buffer zone around the nozzle team, but only when smoke is removed through tactical ventilation is this hazard fully mitigated.

Understanding is Critical

The difficulty that some firefighters have in accepting positive pressure ventilation or positive pressure attack is frequently rooted in a lack of understanding. In some cases, this based on dogmatic attachment to other tactical approaches. In other cases, it is a result of too much training (how to do it) and not enough education (why, why not, and when). Kriss emphasizes the value of positive pressure ventilation and the need to balance training and education to develop both skills proficiency and understanding.

Friendly Criticism

The concluding paragraph of Kriss’s article Education vs. Training in Fire Space Control (Fire Engineering, September 2008) makes two strong statements.

Regardless of the approach we use to safely control fires, we must maintain as the basis of all discussions our ability to control the fire space prior to opening it. The most dramatic means of accomplishing this is through control of the interior environment with [positive pressure attack] PPA and direct water application.

I am fully in agreement with the first sentence. Maintaining control of the fire space is absolutely critical to safe and effective offensive operations. However, the second sentence, which so emphatically supports PPA integrated with direct attack without qualifying the conditions under which this tactic should or should not be used, could be a bit misleading. Under many conditions, PPA and direct attack will be extremely effective. In other circumstances, these tactics are not appropriate. For example, Positive Pressure Attack for Ventilation and Firefighting by Garcia, Kauffmann, and Schelble, identifies several contraindications to use of PPA, inclusive of victims in the exhaust opening or other area which may be threatened and extremely ventilation controlled fire conditions which may present risk of backdraft.

The metaphor of the silver bullet applies to any straightforward solution perceived to have extreme effectiveness. The phrase typically appears with an expectation that some new technology or practice will easily cure a major prevailing problem. (Wikipedia)

In firefighting there are no silver bullets. Increased understanding of the theoretical foundations of fire behavior and the influence of ventilation and applied research such as that done by the National Institute for Standards and Technology are the key to effective use of ventilation strategies and improving the safety and effectiveness of fireground operations.

Firefighters should not uncritically accept current practice. Neither should firefighters accept new or different approaches without the same thoughtful and critical examination. Not just what and how, but why! Kriss’s Positive Pressure Attack website has a wide range of resources related to positive pressure ventilation and positive pressure attack. As Kris advises, both education and training are critical to safe and effective firefighting. Positive pressure attack is an extremely powerful tool when used correctly, be a student of your craft and learn not just what and how, but why!

Kris also published an article titled The Power of Negative Thinking in October issue of FireRescue magazine. This article takes a look at how pressure differences inside and outside the fire building influence ventilation. This interesting article will be the focus of a future post.

Ed Hartin, MS, EFO, MIFireE, CFO