Posts Tagged ‘Tactical Ventilation’

Public Stakeholder Meeting

On 19 November 2008, National Institute for Occupational Safety and Health (NIOSH) will conduct a public stakeholder meeting to gather input on the Firefighter Fatality Investigation and Prevention Program. This meeting has a similar focus to one held on 22 March 2006 in Washington DC. At the 2006 stakeholder meeting, NIOSH received Input from a diverse range of fire service stakeholders. Feedback was extremely supportive of the program, but provided input on potential improvements to this extremely important program. In 2006, I gave a brief presentation that focused on several key issues:

• The upward trend in the rate of firefighter fatalities due to trauma during offensive, interior firefighting operations.
• Failure of NIOSH to adequately address fire behavior and limited understanding of fire dynamics as a causal or contributing factor in these fatalities.

The issues that I raised at the 2006 stakeholder meeting continue to be a significant concern. In 2007, extreme fire behavior was a causal or contributing factor in 17 firefighter line of duty deaths (LODD) in the United States. Where these incidents were investigated by NIOSH, the investigations, subsequent reports, and recommendations did not substantively address the fire behavior phenomena involved nor did they provide recommendations focused on improving firefighters and fire officers understanding of practical fire dynamics.

Ongoing Challenges

In the 20 months since the 2006 stakeholder meeting, NIOSH has implemented a number of stakeholder recommendations. However, Death in the line of duty reports continue to lack sufficient focus on fire behavior and human factors issues contributing to traumatic fatalities during offensive, interior firefighting operations.

Where these reports could provide substantive recommendations for training and operations that would improve firefighter safety, they continue to provide general statements reflecting good practice. While the recommendations contained in NIOSH Death in the line of duty reports, are correct and critically important to safe and effective fireground operations, they frequently provide inadequate guidance and clarity.

In incidents involving extreme fire behavior, investigators frequently fail to adequately address the fire behavior phenomena involved and the implications of the action or inaction of responders. In addition, while training is addressed in terms of national consensus standards or standard state fire training curriculum, there is no investigation as to how the level of training in practical fire dynamics, fire control, and ventilation strategies and tactics may have impacted on decision making.

Presentation of these issues in general terms does not provide sufficient clarity to guide program improvement. Examination of a recent death in the line of duty report will be used to illustrate the limitations of these important investigations and reports in incidents where extreme fire behavior is involved in LODD.

Death in the line of duty… F2007-29

There are many important lessons to be learned from this incident and the limited information presented in this report. However, this analysis of Report F2007-29 focuses on fire behavior and related tactical decision-making. This analysis is completed with all due respect to the individuals and agencies involved in an effort to identify systems issues related to the identification and implementation of lessons learned from firefighter fatalities.

On August 3, 2007 Captain Kevin Williams and Firefighter Austin Cheek of the Noonday Volunteer Fire Department lost their lives while fighting a residential fire. Neither this information nor any reference to the report on Firefighter Fatality Investigation FY 07-02 released by the Texas State Fire Marshal’s Office was included in NIOSH Death in the line of duty report F2007-29. This is critical to locating additional information regarding the incident. Even more importantly, it is important to remember that firefighter LODD involve our brother and sister firefighters, not simply “Victim #1″� and “Victim #2”.

Reading the Fire

This incident involved a 2700 ft², wood frame, single family dwelling. The fire was reported at 0136 and the first unit arrived on scene at 0150. The crew of the first arriving engine deployed a 1-3/4″� (45 mm) hoseline and positive pressure fan to the door on Side A. NIOSH Report F2007-29 reported that the attack team made entry at 0151 but backed out a few minutes later due to flames overhead just inside the front door and that positive pressure was initiated at 0156 prior to the attack team re-entering the building.

However, the Texas State Fire Marshal’s Report FY 07-02 indicated the following:

Flint-Gresham Engine 1 arrived on scene at 01:50:21 positioning short of Side A� and reported, “On location, flames visible.”�

Firefighters Joshua Rawlings and Ben Barnard of the Flint-Gresham VFD pulled rack line 2, a 200� long 1.3/4” (45 mm) � line, to the front door on Side A.� Flint-Gresham VFD Firefighter Robles conducted a quick survey of the north side and then positioned the vent fan at the front door to initiate Positive Pressure Ventilation (PPV). Robles stated that the PPV was set and operating prior to entry by the first attack team. Robles stated that he started to survey the south side and noted heavy black smoke from the top half of a broken window. He stated that he reported this to the IC.

Flint-Gresham Firefighters Barnard (nozzle) and Rawlings (backup) entered through the open front door and advanced 8-10 feet on a left hand search. This attack team noted flames rolling across the ceiling moving from their left to their right as if from the attic. Rawlings stated that flames were coming out of the hallway at the ceiling area and around the corner at a lower level. Barnard reported the hottest area at the hallway. The interior attack team then backed out to the front doorway and discussed their tactics. After a brief conversation, Rawlings took the nozzle with Barnard backing him and they re-entered. They entered approximately 10 feet and encountered flames rolling from their left to their right. They used a “penciling technique”� aimed at the ceiling to cool the thermal layer. Rawlings reported in interview that there was an increase in heat and decrease in visibility as the thermal layer was disrupted and heat began to drop down on top of them.

There is an inconsistency between the NIOSH and Texas State Fire Marshal’s reports regarding the timing of the positive pressure ventilation. The NIOSH report indicates that positive pressure was applied between the first and second entries by the attack team. However, in the Fire Marshal’s report, Firefighter Robles is quoted as stating that positive pressure was applied before entry. This seems to be a minor point, but if effective, positive pressure ventilation would have significantly changed the fire behavior indicators observed from the exterior and inside the building. Recognition of this discrepancy along with a sound understanding of practical fire dynamics would have pointed to the ineffectiveness of tactical ventilation and potential for extreme fire behavior.

The NIOSH report did not identify the fire behavior indicators initially observed by Firefighter Robles or the attack team, nor did they draw any conclusions regarding the stage of fire development, burning regime (fuel or ventilation controlled), or effectiveness of the positive pressure ventilation.

NIOSH Report F2007-29 did not speak to the fact that none of the first arriving personnel verified the size and adequacy of the existing ventilation opening, the potential implications of inadequate exhaust opening size, and the need to verify that the positive pressure ventilation was effective prior to entry. In addition, the initial attack crew observed flames moving toward the point of entry, which would not be likely if the positive pressure ventilation was effective. However, no mention was made in the NIOSH report regarding conditions inside building and the observations of the attack team.

Window size is not specified, but it is likely that the opening was significantly less than the area of the inlet being pressurized by the fan. Inadequate exhaust opening area leads to excessive turbulence, mixing of hot smoke (fuel) and air, and can lead to extreme fire behavior such as vent induced flashover or backdraft. Recognition of this discrepancy along with a sound understanding of practical fire dynamics would have pointed to the ineffectiveness of tactical ventilation and potential for extreme fire behavior.

In reading this case study, it would be useful for the reader to be able to make a connection between key fire behavior indicators, the decisions made by on-scene personnel, and subsequent fire behavior. The NIOSH report did not identify the indicators initially observed by interior or exterior crews, nor did it draw any conclusions regarding the stage of fire development, burning regime (fuel or ventilation controlled), or effectiveness of the positive pressure ventilation, all of which were likely factors influencing the outcome of this incident.

NIOSH Report F2007-29 indicated that the attack team exited the building at 0213 due to low air and reported that the fire was knocked down, identified the location of a few hot spots, and that smoke conditions were light. The report follows to indicate that one of the chief officers did a walk around two minutes later and observed smoke in all the windows and smoke coming from the B/C and C/D corners of the structure. However the Texas State Fire Marshal’s Report 07-02 stated:

Firefighters Rawlings and Barnard penciled the rolling flames in the thermal layer until Rawlings’s low air alarm sounded. The Incident Commander, Captain Williams and Firefighter Cheek met Firefighters Rawlings and Barnard at the front door and a briefing occurred. Firefighters Rawlings and Barnard reported to Asst. Chief Baldauf they had the hot spots out. Rawlings stated in a later interview that they told Williams and Cheek they knocked down the fire and only overhaul was needed.

At 02:13, Captain Williams and Firefighter Cheek entered the structure as attack team 2, using the same line previously utilized by Firefighters Rawlings and Barnard.

Exterior crews from Noonday and Bullard started horizontal ventilation by breaking a window out on Side C (north side). Noonday Chief Gary Aarant performed a walk around, then reported heavy smoke from the B/C,and C/D� corners and at 02:15:51 asked if vertical ventilation had been started. Command then gave the order to begin vertical ventilation.

Understanding what occurred in this incident requires more than the cursory information provided in the NIOSH report. Developing the understanding of critical fire behavior indicators is essential to situational awareness. Discussion of fire behavior indicators and their significance in NIOSH reports would provide an excellent learning opportunity. For example, in this incident, the difference between “smoke” as described in the NIOSH report and “heavy smoke” as reported in the Texas State Fire Marshal’s report is likely a significant difference in assessment of conditions from the exterior of the building (particularly if this is a change in conditions).

NIOSH Report F2007-29 made brief mention of smoke discharge from the point of entry which was being used as the inlet for application of positive pressure. “At 0236 hours, heavier and darker smoke began pushing out of the entire front door opening and overriding the PPV fan”. However, the report does not speak to the significance of this indicator of impending extreme fire behavior.

The Texas State Fire Marshal’s Report 07-02 included a series of photographs provided by the Bullard Fire Department which provided a dramatic illustration of these key smoke and air track indicators. Inclusion of these photographs in the NIOSH report would have aided the reader in recognizing this key indicator of ineffective tactical ventilation and imminent potential for extreme fire behavior.

Photo of Conditions on Side A at 0210

Bullard Fire Department Photo/Texas State Fire Marshal’s Report

Photo of Conditions on Side A at 0217

Bullard Fire Department Photo/Texas State Fire Marshal’s Report

Photo of Conditions on Side A at 0223

Bullard Fire Department Photo/Texas State Fire Marshal’s Report

NIOSH Report F2007-29 addresses the need for the incident commander to conduct a risk versus gain analysis prior to and during interior operations. However, the report does not address the foundational skill of being able to read fire and predict likely fire behavior as a part of that process. In addition, reading the fire and dynamic risk assessment are not solely the responsibility of the incident commander. Everyone on the fireground must be involved in this process within the scope of their role and work assignment. For example, the initial and subsequent attack teams were in a position to observe critical indicators that were not visible from the exterior.

While there is no way to tell, it is likely that if Captain Williams and Firefighter Cheek recognized the imminent probability of extreme fire behavior or the significance of changing conditions they would have withdrawn the short distance from their operating position to the exterior of the building. Likewise, if the incident commander or others operating on the exterior recognized deteriorating conditions earlier in the incident it is likely that they would have taken action sooner to withdraw the crew working on the interior.

Understanding practical fire dynamics, recognition of key indicators and predicting likely fire behavior is a critical element in situational awareness and dynamic risk assessment. Fire behavior and fire dynamics receive limited focus in most standard fire training curricula. It is important that NIOSH examine this issue when extreme fire behavior is a causal or contributing factor in LODD.

My next post will continue with the analysis of NIOSH Report F2007-29 and will make specific recommendations for program improvement.

Ed Hartin, MS, EFO, MIFireE, CFO

Fire Ventilation by Stefan Svensson was originally written to support ventilation training delivered by the Swedish Rescue Services Agency (R�ddnings Verket). However, the English translation of this text is an excellent resource for any firefighter or fire officer.

Stefan does an excellent job of integrating practical fireground experience and the underlying science of thermodynamics and fluid dynamics that are essential to really understanding ventilation. Many of the concepts presented in this text will be familiar to firefighters anywhere in the world. Topics include:

1. Fire Ventilation
2. Fire Behavior
3. Fire Gases
4. The Spread of Fire Gases
5. Working with Fire Ventilation
6. Creating Openings
7. Safety When Working at high Altitudes
8. Openings in Different Roof Structures
9. Tactics
10. Examples of Firefighting Situations

The chapters on fire ventilation, fire behavior, and fire gases, were a necessary introduction to the topic, but other texts provide a more comprehensive examination of these important subjects. The chapters that I found most useful were The Spread of Fire Gases and Working with Fire Ventilation. Stefan’s explanation of influences on smoke movement, influence of inlet and outlet opening size, and other factors that impact the effectiveness and efficiency of ventilation operations is excellent. The narrative is simple and straightforward and shaded boxes highlight mathematical formula and calculations necessary for those who want to engage with this topic at a deeper level.
For individuals without an engineering background, the mathematical explanations of the underlying principles and engineering applications may seem a bit daunting. More detailed explanation and worked examples would provide better support of this content. However, this is a minor issue which does not significantly compromise the utility of this text to a wide range of audiences.
Fire Ventilation is available for on-line purchase from the Swedish Rescue Services Agency for 120 SEK (around $16.00) plus shipping. The agency will invoice for payment Swedish Kroner after your purchase (which necessitates using a bank that can produce a check in foreign currency).

NIOSH Public Meeting

On November 19, 2008, the National Institute for Occupational Safety and Health will be conducting a public stakeholder meeting regarding the Firefighter Fatality Investigation and Prevention Program. This meeting will be held at 1000 hours at the Crown Plaza Hotel at Chicago’s O’Hare Airport. My next post will provide a preview of my presentation at this meeting and written testimony submitted for inclusion in the public docket. Take a minute to review NIOSH Report F2007-29 before Thursday’s post.

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

Many firefighters consider Positive Pressure Ventilation (PPV) to be a new tactical approach, despite practical application in the United States since the 1980s. Since its inception, PPV has strong advocates and equally strong opponents. In many cases these opinions sprang from observation of inappropriate application of PPV without a sound understanding of how this tactic actually works. Early on there was little scientific research integrated with practical application of PPV tactics.

However, over the last six years the National Institute of Standards and Technology (NIST) has been conducting an ongoing program of research to identify how PPC works, factors influencing effectiveness in varied applications, and best practices in the application of this tactic. Steve Kerber served as principal investigator on this project. Steve is a fire protection engineer (who also serves as a volunteer Chief Officer in Prince Georges County, Maryland). Steve authored an excellent article titled NIST Goes Back to School published in the September/October issue of NFPA Journal.

This article provides a brief overview of the NIST research on PPV to date and outlines a series of tests conducted in a two-story, 300,000 ft²(27,871 m²) retired high school in Toledo, Ohio, to examine the ability of PPV fans to limit smoke spread or to remove smoke from desired areas in a large low-rise structure.
Steve pointed out the effectiveness of appropriate use of PPV as demonstrated in this series of tests, observing:

In this limited series of experiments the pressure was increased sufficiently to: reduce temperatures, giving potential occupants a more survivable environment and increase fire fighter safety, limit smoke spread, keeping additional parts of the structure safe for occupants and undamaged and reducing the scale of the emergency for the fire fighters, and increase visibility, allowing occupants a better chance to self evacuate and providing fire fighters with an easier atmosphere to operate in. Positive pressure ventilation is a tool the fire service can utilize to make their job safer and more efficient.

However, Steve also provided the following cautionary advice:

Ventilation of oxygen limited or fuel rich fires, either naturally or mechanically, can cause rapid fire growth. Ventilation is not synonymous with cooling. Venting was most effective when coordinated with other operations on the fire ground.

Strong advocates of PPV and positive pressure attack (PPA) such as Battalion Chiefs Kris Garcia and Reinhard Kauffmann, authors of Positive Pressure Attack for Ventilation and Firefighting also caution against use of positive pressure ventilation under extremely ventilation controlled/fuel rich conditions due to backdraft potential.

However, there is no clear line defining when fire conditions are sufficiently ventilation controlled to preclude safe and effective use of positive pressure as a ventilation tactic. Safe and effective use of this tactic requires a sound understanding of practical fire dynamics and the potential influence of tactical operations. This reinforces the ongoing need for scientific research and integration of theory and practical fireground experience in defining best practices in tactical ventilation.

NIST Technical Note 1498, Evaluating Positive Pressure Ventilation in Large Structures: School Pressure and Fire Experiments as well as reports related to NIST’s prior PPV research are available at the Fire.Gov web site. Downloadable video footage is also available for each of these NIST PPV tests.

Ed Hartin, MS, EFO, MIFireE, CFO