Archive for the ‘Extreme Fire Behavior’ Category

In the Grading the Fireground on a Curve, published in the September issue of Firehouse magazine, Battalion Chief Mark Emery warned of the hazards of assuming that limited volume and velocity of visible smoke indicates a growth stage fire. He correctly identified that compartment fires may enter the decay phase as fuel is consumed or due to a lack of oxygen.

Emery cites National Institute for Occupational Safety and Health (NIOSH) Death in the Line of Duty reports 98-F07 and F2004-14, in which firefighters initiated offensive fire attack in commercial buildings and encountered rapidly deteriorating fire conditions due to changes in the ventilation profile. Concluding the introduction to his article, Emery observes “Unless you know which side of the fire growth curve you are entering, advancing into zero-visibility conditions is really a bad idea”.

I agree with BC Emery’s basic premise that appearances can be deceiving. However, this article points to two interrelated issues. The hazards presented by ventilation controlled fires and the dangerous conditions presented by enclosed buildings. In Smoke Burns,originally published on Firehouse.com I discussed the hazards of ventilation controlled fire and the relationship of burning regime to extreme fire behavior phenomena such as flashover and backdraft. The hazards presented by ventilation controlled fires are compounded when the fire occurs in an enclosed structure (a building with limited means of access and egress). Captain Willie Mora has written extensively on Enclosed Structure Disorientation on Firehouse.com.

BC Emery illustrated how appearances can be deceiving using data and still images from a full scale fire test in a warehouse in Phoenix, Arizona conducted by the National Institute for Standards and Technology (NIST). NIST conducted these tests as part of a research project on structural collapse. However, the video footage and temperature data from this test is extremely useful in studying the influence of ventilation on fire behavior and fire behavior indicators (Building, Smoke, Air Track, Heat, and Flame (B-SAHF)). The full report and video from this test is available on-line from the NIST Building Fire Research Laboratory (BFRL).

As an oxidation reaction, combustion requires oxygen to transform the chemical potential energy in fuel to thermal energy. If a developing compartment fire becomes ventilation controlled, with heat release rate limited by the oxygen available in the compartment, pyrolysis will continue as long as temperature in the compartment is above several hundred degrees Celsius. Pyrolysis products in smoke are gas phase fuel ready to burn. Increased ventilation at this point, may cause the fire to quickly transition to the fully developed stage (ventilation induced flashover). However, if the fire continues to burn in a ventilation controlled state and the concentration of gas phase fuel (pyrolysis products and flammable products of incomplete combustion) increases sufficiently, increased ventilation may result in a backdraft.

I take issue with BC Emery’s illustration of the growth side of the fire development curve as the value side of the cure and the decay side of the curve as the no value side of the curve. Depending on resources, a fire on the growth side of the curve may exceed the offensive fire control capability of the fire department. Conversely, a fire on the decay side of the curve which is limited to a single compartment or series of compartments may be effectively controlled using an appropriate tactics in an offensive strategic mode. However, Emery’s discussion of the more subtle indicators of burning regime that may warn firefighters of a ventilation controlled fire is right on track. For more information on fire behavior indicators and fire development, see Fire Behavior Indicators and Fire Development Parts I and II on Firehouse.com.

Ed Hartin, MS, EFO, MIFireE, CFO

Firefighter survival skills, MAYDAY, and rapid intervention training have received a great deal of emphasis over the last several years. These skills are critical. Firefighters must react correctly when faced with a breathing apparatus malfunction, structural collapse, or extreme fire behavior event. However, the most effective approach to survival is to prevent or reduce the probability of firefighters from facing these conditions.

My last several posts have examined the events surrounding a multiple firefighter injury incident that occurred at a residential fire in Loudoun County, Virginia on May 25, 2008. The report prepared by Loudoun County Fire, Rescue, & Emergency Management took a systems approach to examining this incident and the investigative team made 123 recommendations for improving department operations, firefighter safety, communications, behavioral health, training, apparatus and equipment, uniforms and personal protective equipment, and other considerations. This post will examine four of those recommendations that deal with firefighter safety and training. Read the report for additional detail and to examine the other recommendations.

Recommendation: Reiterate the importance of visualizing the entire structure prior to making entry [whenever possible].

Recommendation: Develop a system-wide training program that focuses on situational awareness, particularly how to “read” interior and exterior smoke conditions to identify the location and predicted spread of the fire.

Recommendation: Implement ongoing, mandatory, system-wide training on Northern Virginia MAYDAY procedures and self-survival techniques. In post incident interviews, all four interior personnel credited their escape from the structure with ongoing self-survival training.

Recommendation: Develop and implement system-wide, entry-level and ongoing firefighter self-survival training that at a minimum addresses RIT, flashover, MAYDAY procedures, crew integrity, ladder bails, emergency SCBA procedures, firefighter drags and carries and practical scenario-based evolutions.

These recommendations are excellent, but do not go far enough!

Visualizing the entire structure whenever possible and “reading” smoke conditions on the exterior and interior are a critical component in developing awareness of incident conditions and predicting anticipated fire development and spread. However, smoke is only one fire behavior indicator; a more comprehensive approach integrates assessment of Building, Smoke, Air Track, Heat, and Flame (B-SAHF) indicators along with a sound understanding of practical fire dynamics.

Flashover training often focuses on recognition of late (interior) indicators of this extreme fire behavior phenomena and last minute control efforts to increase the chance of escape and survival. In discussing the flashover training attended by the Loudon County firefighters and officers involved in this incident, the report states:

If flashover is imminent, firefighters are taught to practice aggressive cooling with a 30^o fog pattern to the right, to the center, and to the left.

If this tactic fails, firefighters are directed to get as close to the floor as possible, open the nozzle fully, on a wide fog pattern, and rotate the nozzle about their head in a circular pattern.

Unfortunately, many flashover training programs teach these methods, but do not substantively address use of gas cooling and ventilation tactics to control the fire environment and prevent the occurrence of flashover or other extreme fire behavior phenomenon.

Several years ago, Phoenix Fire Department implemented an initiative that placed 75% of the effort into training to stay out of trouble and 25% into getting out of trouble if it happened. The same principle applies in addressing the hazards presented by potential for extreme fire behavior such as flashover. In addition to survival skills, firefighters must receive training and education to develop the ability to:

• Understand and apply practical fire dynamics on the fireground
• Read critical fire behavior indicators, understand the impact of tactical operations, and predict likely fire behavior
• Understand and skillfully apply fire control and ventilation strategies on a proactive basis to mitigate hazards and control the fire environment

Ed Hartin, MS, EFO, MIFireE, CFO

Previous posts examined key factors and initial company operations at a residential fire involving flashover that resulted in multiple firefighter injuries at a residential fire in Loudoun County, Virginia. This post will examine the action taken by the trapped firefighters and crews on the exterior.

Reserve Engine 6 was performing fire attack on Floor 2 and Tower 6 had just completed searching the second floor when they experienced a rapid increase in temperature and thickening smoke conditions. Flames were extending from the first floor, up the open foyer and staircase, trapping the two crews on Floor 2.

When the firefighter from Reserve Engine 6 opened the nozzle, the line immediately lost pressure. The engine company officer attempted to diagnose the problem without success. Unknown to the engine crew, the hoseline had partially failed approximately 10′ from the nozzle, drastically reducing the available flow. Lacking an effective stream, the engine crew moved down the hallway towards Bedroom 2 in an attempt to find an alternate means of egress.

Partial collapse of the ceiling separated the Tower 6 firefighter and officer. The firefighter joined up with the crew from Reserve Engine 6 in Bedroom 2. The Tower 6 firefighter partially closed the bedroom door, providing some relief from the increasing temperature. The two firefighters and officer trapped in Bedroom 2 were able to escape over a ladder placed on Side Charlie by the apparatus operator of Reserve Engine 6. It is likely that this quick action by the tower firefighter in closing the door had a significant impact on the tenability of Bedroom 2 for the time required for these three individuals to escape.

Trapped in the Master Bedroom, the officer from Tower 6 attempted to break a window to escape the increasing temperature and thick smoke, but was unable to do so. He exited the master bedroom and eventually escaped through an unspecified window on Floor 2, Side Charlie.

Several factors contributed to the survival of the crews working on floor 2:

• Proper use of personal protective equipment
• Recognition of rapidly deteriorating conditions
• Immediate action to locate an alternate means of egress
• Availability of a secondary egress route provided by the ladders placed by the apparatus operators of the tower and engine
• Closing of the door to Bedroom 2 to increase tenability during emergency egress

Read the report for additional detail on this incident.

The crews of Reserve Engine 6 and Tower 6 who were on Floor 2 had completed survival skills and flashover training. Training and quick reactions contributed to their survival, but increased situational awareness, earlier recognition of developing fire conditions, and control of the fire environment would likely have prevented this accident.

The next post will examine key issues in training focused on “reading smoke” as well as flashover and survival skills training.

Ed Hartin, MS, EFO, MIFireE, CFO

My last post provided an overview of the factors influencing the occurrence of flashover and multiple firefighter injuries at a residential fire in Loudoun County Virginia identified in the report released by Loudoun County Fire, Rescue, and Emergency Management. Let’s look at the events that occurred from the time of dispatch until flashover occurred.

Loudoun County Emergency Communications Center (ECC) dispatched four engines, a truck, rescue, ambulance and two chief officers were dispatched to a reported house fire at 43238 Meadowood Court. The caller reported a fire in the area of the sunroom on the first floor of the home at this address with smoke coming from the roof. Subsequent callers reported heavy smoke in the area. While the call taker received information about the location of the fire in the building, the dispatcher did not pass this information to responding companies.

The first arriving company, Reserve Engine 6 reported that the building was a two-story, single-family dwelling with a fire in the attic or running Side Charlie. Uncertain of the status of building occupants, the engine company officer assigned the truck to perform primary search.

As part of his size-up, the engine company officer walked from Side Alpha around Side Delta to the Charlie/Delta corner to assess conditions. Unfortunately, from this position, he was unable to observe the fire in the area of the sunroom on Floor 1; this factor would become extremely significant over the next seven minutes.

Reserve Engine 6 was staffed with a crew of three, and the firefighter and officer extended a 200′ 1-3/4″ (60.96 M 45 mm) preconnected hoseline to the door on Side Alpha. As the hoseline was being deployed Tower 6, also with a crew of three, arrived on scene and the tower officer and firefighter joined the engine crew at the front door.

When they entered the building, the crews of Reserve Engine 6 and Tower 6 encountered moderately thick smoke and no significant increase in temperature in the two-story (open) foyer. The smoke was thick enough that they had some difficulty in locating the interior staircase. There is no indication that either crew picked up on the presence of significant smoke on Floor 1 as a violation of their expectation of a fire on Floor 2 or in the attic or a potential indicator that there may be a fire on Floor 1.

As they proceeded up the stairs, the crews of Reserve Engine 6 and Tower 6 did not encounter an appreciable change in conditions. Smoke remained moderate, with no significant increase in temperature. Reaching the top of the stairs, the engine crew turned right towards the Master Bedroom. The crew from Tower 6 went left into Bedroom 1 and conducted primary search, venting a window on Side Alpha. The report does not mention if the crew of Tower 6 closed the door to the bedroom while conducting their search or the position of the door when they completed their search of this room and continued to Bedroom 2.

Computer modeling of fire development in this incident has not yet been completed and the report does not indicate that this change in ventilation profile was a significant factor in the occurrence of flashover or extension of flames to Floor 2. However, presence or creation of an air track with crews working between the fire and exhaust opening has been a factor in other incidents. For example, see NIOSH Report 99-F21 and F2000-04 as well as NIST Reports 6854 and 6510.

Entering the master bedroom, the crew of Reserve Engine 6 encountered thick smoke, an increase in temperature, and observed flames on the opposite side of the room (Side Charlie). The officer directed the firefighter to attack the fire while he opened a window on Side Charlie. Tower 6 completed the primary search of Bedroom 2 (no mention of the tower crew making any ventilation openings in Bedroom 2) and then completed a search of Bedroom 3. After finishing the search of Floor 2, the Tower determined the need to pull ceilings for Reserve Engine 6, but doe to the height of the ceiling, did not have tools long enough to accomplish this task.

While crews were working on the interior, the apparatus operator of Tower 6 placed a ladder on Side Alpha to a window in Bedroom 3, removing approximately 2/3 of the glass from the opening. The apparatus operator of Reserve Engine 6 placed a ladder on Side Charlie to a window in Bedroom 2, which broke, but did not remove the glass.

A chief officer arrived and assumed Command on Side Alpha. Command assigned the second chief, who arrived a short time later to perform reconnaissance on Side Charlie. In his transfer of command radio report, the officer of Reserve Engine 6 indicated that the fire was in the attic. Command confirmed that there were flames visible from the attic ridge vents and flames were visible from both sides.

On the interior, the crews of Reserve Engine 6 and Tower 6 experienced a rapid increase in temperature and thickening smoke conditions. The crew of Tower 6, who were exiting to obtain longer tools, encountered flames coming up the open foyer and staircase from the first floor.

MAYDAY, MAYDAY, MAYDAY! Due to a problem with his radio, the tower officer, directed his firefighter to transmit a Mayday message. Concurrently, second arriving chief reported a collapse on Side Charlie.

As with many other incidents resulting in serious injuries or fatalities, this “appeared to be a routine incident”. Companies initiated standard firefighting tactics based on their assessment of incident conditions and the problems presented. The following three events contributed significantly to limited situational awareness:

1. Limited information provided by dispatch
2. Completing a 180^oreconnaissance rather than viewing all sides of the structure
3. Not recognizing key smoke indicators (location, thickness) on Floor 1

While not identified in the report, changing the ventilation profile by opening windows on Floor 2 (possibly based on the assumption that the fire was on Floor 2 or in the attic and the placement of a hoseline by Reserve Engine 6) may have had a negative influence on fire behavior. On the other hand, the placement of ladders to second floor windows by the apparatus operators of the engine and tower provided alternate means of egress for the crews trapped on Floor 2.

Read the report for additional detail on this incident.

The next post will examine the actions taken by Reserve Engine 6 and Tower 6 that aided in their escape from the extreme conditions encountered on Floor 2.

Ed Hartin, MS, EFO, MIFireE, CFO

Earlier this month the Loudoun County Department of Fire, Rescue, and Emergency Management releases a report flashover in a single family dwelling which resulted in injury to six firefighters and one EMS provider. Four firefighters received serous burn injuries, two sustained other traumatic injuries, and the EMS provider experienced minor respiratory distress. This extremely detailed report examines the multiple factors adversely influencing the sequence of events resulting in these injuries.

• Lack of supplemental information to responding companies regarding the location of the fire within the building
• Limited situational awareness based on lack of a 360^o size-up and failure to recognize key fire behavior indicators pointing to potential of a first floor fire
• Working above the fire by initiating fire attack on Floor 2, based on the assumption that this incident involved an attic fire based on fire behavior indicators visible from Side A
• Limited staffing on the first arriving units and delay in arrival of additional resources taxed the capability of the initial companies operating at the incident, negatively influencing situational awareness
• Building construction, lack of compartmentalization in the open floor plan dwelling, and significant fire load contributed to fire development and occurrence of flashover and a partial collapse on Floor 2

However, the investigation also pointed to a number of factors that positively influenced the outcome of the incident.

• Quick and appropriate response to escape from the building once conditions deteriorated and water supply was lost to the attack line
• Rapid placement of ladders to provide secondary egress from Floor 2
• Immediate acknowledgment of the Mayday and recognition of the need to abandon the building
• Completion of Mayday: Firefighter Down curriculum and Flashover training
• Stability of dimensional lumber supporting Floor 2 allowing members on the interior time to escape
• Performance of personal protective equipment, limiting the extent of injuries

The investigators took a broad based, systems approach in examining this incident. Read this report and evaluate the applicability of the lessons learned to your own organization. The next several posts will examine fire behavior, situational awareness, and tactical factors in this incident and recommendations made by the investigative panel

Ed Hartin, MS, EFO, MIFireE, CFO