Archive for the ‘Fire Behavior Training’ Category

FAQ-Fire Attack Questions

Sunday, April 14th, 2013

Captain Mike Sullivan with the Mississauga Ontario Fire Department and I are continuing our dialog with another series of questions related to the science behind fire attack and fire control methods.

The first several questions pertain to the video produced by the Kill the Flashover project illustrating the impact of anti-ventilation on heat release rate and compartment temperature.

Would you happen to know what type of building this was done in (house or concrete burn building) and what fuel was used?

KTF 2011 and 2012 were conducted  in acquired structures and KTF 2013 was conducted in a purpose built burn building. Each of the KTF burns used normal types of building contents to provide realistic fire conditions for the demonstrations/experiments. The first burn in KTF 2011 use a fuel load consisting of a chair, small amount of wood, carpet and carpet pad (as illustrated below).

ktf_2011_burn_1

You mentioned in the “Kill the Flashover” video about the key to heat reduction is the lack of oxygen for the heat release. I understand this but still wonder where all this heat goes, does it not have to dissipate somewhere?

The following video was shot during the first burn in KTF 2011. As previously discussed, the fuel load was comprised of a chair, carpet, carpet pad, and a small amount of wood. At the start of the burn the only opening to the compartment was a typical sized residential doorway. After the fire became well developed the door was closed.

You are absolutely correct! A compartment fire is an open thermodynamic system in which there is an ongoing transfer of mass (e.g., smoke out and air in) and energy between the system and its environment. This leads to another excellent question.

We often speak about fire and how the box “can’t absorb any more heat” and this is usually the point where we start to near flashover, this is what we thought was occurring, the box was simply continuing to absorb heat.

The phrase “can’t absorb any more heat” is scientifically incorrect, unless the “box” and the flames or hot gases are all of equal temperature. If any portion of the compartment or fuel packages within the compartment are lower than the temperature of flames or hot gases, the temperature of this matter will continue to increase (until thermal equilibrium is reached). The oversimplified explanation likely relates to the endothermic (heat absorbing) process of pyrolysis and transition to the exothermic (heat releasing) process of combustion.

Any object with a temperature above absolute zero transfers thermal energy to objects having a lower temperature. In a compartment fire energy released by the combustion reaction is transferred to materials within the thermodynamic system through radiation, conduction, and convection (as illustrated below).

thermodynamic_system_actual_compartment

Under fire conditions, increasing temperature in the compartment is the result conversion of chemical potential energy in the fuel to thermal energy through combustion. When the rate of energy released exceeds losses of thermal energy to the thermodynamic surroundings, temperature increases. When heat release rate is reduced by limiting the oxygen available for combustion (i.e. closing the door), continued transfer of energy to the thermodynamic surroundings results in a drop in temperature.

This is somewhat like bringing a pot of water on the stove to a boil and then removing it from the burner. Once off the burner, the water continues to transfer energy to its surroundings and will begin to cool.

boiling_water

 

FAQ-Fire Attack Questions will continue next week with a discussion of gas cooling, fog patterns and solid or straight streams, and limitations encountered when working in large volume spaces!.

“Flashover Training”

Saturday, April 6th, 2013

This week’s questions focus on training firefighters to recognize, prevent, and if necessary react appropriately to flashover conditions. Casey Lindsay of the Garland, Texas Fire Department sent an e-mail to a number of fire behavior instructors regarding how they conduct “flashover training”

One of the challenges we face in discussing fire behavior training, particularly live fire training is the result of variations in terminology. Differences exist in the way that live fire training props are described and in fire control techniques. For this discussion, CFBT-US defines the type of prop pictured below as a “split level demo cell”. This terminology is derived from the original purpose of this design as conceived by the Swedish Fire Service in the 1980s. The split level cell is intended for initial fire behavior training focused on observation of fire development. As used in the United States (and some other parts of the world) it is described as a “flashover simulator” or “flashover chamber”. This provides a disconnect in context as this prop is not intended and does not subject the participants in training to flashover conditions, but simply provides an opportunity to observe fire development through the growth stage and recognize some potential cues of impending flashover.

DSC_0013

Note: The prop illustrated above is a Split level cell at the Palm Beach County Fire Training Center.

Container based props can be configured in a variety of ways for both demonstration and fire attack training. Most commonly single compartment cells are single level or split level design. Multiple compartment cells are arranged in a variety of ways with containers placed in an “L”, “H” or other configuration.

Do you currently teach firefighters that “Penciling control techniques can be used to give firefighters additional time to escape a flashover”?

We define penciling as an intermittent application using a straight stream as compared to pulsing which uses a fog pattern or painting which is a gentle application of water to hot surfaces. We do not teach penciling, pulsing, or painting as a technique to give firefighters additional time to escape flashover. We use gas cooling (short or long pulses) and coordination of fire attack and ventilation to control the environment and prevent or reduce the potential for firefighters to encounter flashover. However, long pulses (or continuous application) while withdrawing is taught as a method of self-protection if fire conditions exceed the capability of the crew engaged in fire attack.

In response to Casey’s questions, Jim Hester, with the United States Air Force (USAF) presents an alternative perspective:

No! We do not teach penciling or 3D Fog attack anymore. We did temporarily after receiving our training as instructors in the flashover trainer. We gave the technique an honest look and conducted research using Paul Grimwood’s theories. We decided there are too many variables. For example; what works in a room and contents [fire] will not work in heavy fire conditions inside a commercial. The last thing we want is someone penciling any fire, inside any structure, that requires constant water application until the fire is darkened down. That’s what we teach.  Open the nozzle for as long as it takes to get knock down and then shut the nozzle down. [It is as] simple as that. If you take that approach, even in the flashover trainer you will alleviate confusion or misapplication of your fire stream.

While I have a considerably different perspective, Jim raises several good points. I agree that there are many variables related to fire conditions and room geometry. If firefighters are trained in lock step manner that short pulses are used to control the temperature overhead, there will definitely be a challenge in transitioning from the container to a residential fire and even more so when confronted with a commercial fire. However, if firefighters are introduced to the container as a laboratory where small fires are used to develop understanding of nozzle technique, rather than a reflection of real world conditions, this presents less of an issue.

As Jim describes, fire conditions requiring constant application in a combination attack with coordinated tactical ventilation, may not be controlled by short pulses. However, when cooling hot smoke on approach to a shielded fire, constant application of water will likely result in over application and less tenable conditions (too much water may not be as bad as too little, but it presents its own problems).

Most firefighters, even those that advocate continuous application, recognize that a small fire in a trash can or smoldering fire in a upholstered chair or bed does not require a high flow rate and can easily be controlled and extinguished with a small amount of water. On the other hand, a fully developed fire in a large commercial compartment cannot be controlled by a low flow handline. To some extent this defines the continuum of offensive fire attack, small fires easily controlled by direct application of a small amount of water and large fires that are difficult to control without high flow handlines (or multiple smaller handlines). There is not a single answer to what is the best application for offensive fire attack. Shielded fires require control of the environment (e.g., cooling of the hot upper layer) to permit approach and application of direct or combination attack. Fires that are not shielded present a simpler challenge as water can be brought to bear on the seat of the fire with less difficulty.

Nozzle operators must be trained to read conditions and select nozzle technique (pulsed application to cool hot gases versus penciling or painting to cool hot surfaces) and fire control methods (gas cooling, direct attack, indirect attack, or combination attack) based on an assessment of both the building and fire conditions.

What flashover warning signs do you cover during the classroom portion of flashover training?

We frame this discussion in terms of the B-SAHF (Building, Smoke, Air Track, Heat, and Flame) indicators used in reading the fire (generally, not just in relation to flashover).

B-SAHF_PHOTO

Building: Flashover can occur in all types of buildings. Consider compartmentation, fuel type, and configuration, ventilation profile, and thermal properties of the structure. Anticipate potential for increased ventilation (without coordinated fire control) to result in flashover when the fire is burning in a ventilation controlled regime (most fires beyond the incipient stage are ventilation controlled). Note that these indicators are not all read during the incident, but are considered as part of knowing the buildings in your response area and assessing the building as part of size-up.

Smoke: Increasing volume, darkening color and thickness (optical density), lowing of the level of the hot gas layer.

Air Track: Strong bi-directional (in at the bottom and out at the top of an opening), turbulent smoke discharge at openings, pulsing air track (may be an indicator of ventilation induced flashover or backdraft), and any air track that shows air movement with increasing velocity and turbulence.

Heat: Pronounced heat signature from the exterior (thermal imager), darkened windows, hot surfaces, hot interior temperatures, observation of pyrolysis, and feeling a rapid increase in temperature while working inside (note that this may not provide sufficient warning in and of itself as it is a late indicator).

Flame: Ignition of gases escaping from the fire compartment, flames at the ceiling level of the compartment, isolated flames in the upper layer (strong indicator of a ventilation controlled fire) and rollover (a late indicator).

How do you incorporate the thermal imaging camera into your flashover class?

We do not teach a “flashover” class. We incorporate learning about flashover (a single fire behavior phenomena) in the context of comprehensive training in practical fire dynamics, fire control, and ventilation (inclusive of tactical ventilation and tactical anti-ventilation). Thermal imagers (TI) are used in a variety of ways beginning with observation of small scale models (live fire), observation of fire development (with and without the TI) and observation of the effects of fire control and ventilation.

Do you allow students to operate the nozzle in the flashover chamber?

We use a sequence of evolutions and in the first, the students are simply observers watching fire development and to a lesser extent the effects of water application by the instructor. In this evolution, the instructor limits nozzle use and predominantly sets conditions by controlling ventilation. If necessary the instructor will cool the upper layer to prevent flames from extending over the heads of the participants or to reduce the burning rate of the fuel to extend the evolution. Students practice nozzle technique (short and long pulses, painting, and penciling) outside in a non-fire environment prior to application in a live fire context. After the initial demonstration burn, students develop proficiency by practicing their nozzle technique in a live fire context.

When working in a single level cell rather than a split level cell (commonly, but inaccurately referred to as a “flashover chamber” or “flashover simulator”) we expand on development of students proficiency in nozzle technique by having them practice cooling the upper layer while advancing and importantly, while retreating. In addition, students practice door entry procedures that integrate a tactical size-up, door control, and cooling hot gases at the entry point.

Do you maintain two-in/two-out during flashover chamber classes?

We comply with the provisions of NFPA 1403 and provide for two-in/two-out by staffing a Rapid Intervention Crew/Company during all live fire training.

What is your fuel of choice for the 4×8 sheets (OSB, Particleboard or Masonite)?

We have used a variety of fuel types, but commonly use particle board. OSB tends to burn quickly, but can be used if this characteristic is recognized. We have also used a low density fiberboard product (with less glue) which performs reasonably well. The key with fuel is understanding its characteristics and using the minimum quantity of fuel that will provide sufficient context for the training to be conducted. I recommend that instructors conduct test burns (without students) when evaluating fuel packages that will be used in a specific burn building or purpose built prop (such as a demo or attack cell).

Do you have benches or seating in the flashover chamber?

No, firefighters are expected to be in the same position that they would on the fireground, kneeling or in a tripod position. When we work in a demo cell (“flashover chamber”) with benches, we keep the students on the floor.

Do you teach any flashover survival techniques, other than retreat/evacuate?

We focus first on staying out of trouble by controlling the environment. Second, we teach firefighters the skill of retreating while operating the hoseline (generally long pulses to control flames overhead). There are not really any options other than control the fire of leave the environment (quickly)! This is similar to James Hester’s answer of continuous flow, with a sweeping motion (long pulses can be applied in a sweeping manner, particularly in a large compartment). It is important to understand that a short pulse is extremely short (as fast as you can open the nozzle) and a long pulse is anything else (from several seconds to near continuous application, depending on conditions).

Refer to the series of CFBT Blog on Battle Drills for additional discussion developing proficiency in reaction to deteriorating conditions.

Additional Thoughts

Our perspective is that discussion of flashover should be framed in the context of comprehensive fire behavior training, rather than as a “special” topic. Practical fire dynamics must be integrated into all types of structural firefighting training, in particular: Hose Handling, Fire Control, and Tactical Ventilation (but the list goes on). When working with charged hoselines, take the time to practice good nozzle technique as well as moving forward and backward (do not simply stand up and flow water when performing hose evolutions). In fire control training (live fire or not), practice door control, tactical size-up, and door entry procedures. When training on the task activity of tactical ventilation (e.g., taking glass or cutting roof openings), make the decision process explicit and consider the critical elements of coordination and anticipated outcome of you actions.

FDIC

Plan on attending Wind Driven Fires in Private Dwellings at Fire Department Instructors Conference, Indianapolis, IN on Wednesday April 24, 2013 in Wabash 3. Representing Central Whidbey Island Fire & Rescue, Chief Ed Hartin will examine the application of NIST research on wind driven fires to fires in private dwellings. achat priligy generique This workshop is a must if the wind blows where you fight fires!

wind_driven_fires_private_dwellings

 

Influence of Ventilation in Residential Structures:
Tactical Implications Part 8

Friday, January 13th, 2012

The eighth and tenth tactical implications identified in the Underwriters Laboratories study of the Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction (Kerber, 2011) are the answer to the question, can you vent enough and the influence of pre-existing openings or openings caused by fire effects on the speed of progression to flashover.

The ninth implication; the effects of closed doors on tenability for victims and firefighters, will be addressed in the next post.

Photo Credit: Captain Jacob Brod, Pineville (NC) Fire Department

Kerber (2011) indicates that firefighters presume that if you create enough ventilation openings that the fire will return to a fuel controlled burning regime. I am not so sure that this is the case. Until fairly recently, the concept of burning regime and influence of increased ventilation on ventilation controlled fires was not well recognized in the US fire service. However, there has been a commonly held belief that increased ventilation will improve interior conditions and reduce the potential for extreme fire behavior phenomena such as flashover. In either case, the results of the experiments conducted by UL on the influence of horizontal ventilation cast considerable doubt on the ability to accomplish either of these outcomes using horizontal, natural ventilation.

The Experiments

In order to determine the impact of increased ventilation, Kerber (2011) compared changes in temperature with varied numbers and sizes of ventilation openings. The smallest ventilation opening in the experiments conducted in both the one and two story houses was when the door on Side A was used to provide the only opening. The largest number and size of ventilation openings was in the experiments where the front door and four windows were used (see Figures 1 and 3)

The area of ventilation openings in experiments conducted in the one-story house ranged from 1.77 m2 (19.1 ft2) using the front door only to 9.51 m2 (102.4 ft2) with the front door and four windows. In the two-story house the area of ventilation openings ranged from 1.77 m2 (19.1 ft2) with front door only to 14.75 m2 (158.8 ft2) using the front door and four windows.

The most dramatic comparison is between Experiments 1 and 2 where a single opening was used (front door) and Experiments 14 and 15 where five openings were used (door and four windows).

One Story House

Experiment 1 was conducted in the one-story house using the door on Side A as the only ventilation opening. The door was opened eight minutes after ignition (480 seconds). Experiment 14 was also conducted in the one-story house, but in this case the door on Side A and four windows were used as ventilation openings. Windows in the living room and bedrooms one, two, and three were opened sequentially immediately after the door was opened, providing more than five times the ventilation area as in Experiment 1 (door only).

Figure 1. Ventilation Openings in the One-Story House

In both Experiment 1 (door only) and Experiment 14 (door and four windows), increased ventilation resulted in transition to a fully developed fire in the compartment of origin (see Figure 2). In Experiment 1, a bi-directional air track developed at the door on Side A (flames out the top and air in the bottom). In Experiment 14, a bi-directional air track is visible at all ventilation openings, with flames visible from the door and window in the Living Room on Side A and flames visible through the window in Bedroom 3. No flames extended out the ventilation openings in Bedrooms 1, 2, and 3. The upper layer in Bedroom 3 is not deep, as such there is little smoke visible exiting the window, and it appears to be serving predominantly as an inlet. On the other hand, upper layer in Bedroom 2 is considerably deeper and a large volume of thick (optically dense) smoke is pushing from the window with moderate velocity. While a bi-directional air track is evident, this window is serving predominantly as an exhaust opening.

Figure 2. Fire Conditions at 600 seconds (10:00)

As illustrated in Figure 3, increased ventilation resulted in a increase in heat release rate and subsequent increase in temperature. It is important to note that the peak temperature in Experiment 14 (door and four windows) is more than 60% higher than in Experiment 1 (door only).

Figure 3. Living Room Temperature 0.30 m(1’) Above the Floor One-Story House

Note. Adapted from Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction (p. 298), by Steve Kerber, 2011, Northbrook, IL: Underwriters Laboratories.

Based on observed conditions and temperature measurement within the one-story house, it is evident that increasing the ventilation from 1.77 m2 (19.1 ft2) using the front door to 9.51 m2 (102.4 ft2) with the front door and four windows did not return the fire to a fuel controlled burning regime and further, did not improve interior conditions.

It is important to note that these experiments were conducted without coordinated fire control operations in order to study the effects of ventilation on fire behavior. Conditions changed quickly in both experiments, but the speed with which the fire transitioned from decay to growth and reached flashover was dramatically more rapid with a larger ventilation area (i.e., door and four windows).

Two Story House

Experiment 2 was conducted in the two-story house using the door on Side A as the only ventilation opening. The door was opened ten minutes after ignition (600 seconds). Experiment 15 was also conducted in the two-story house, but in this case the door on Side A and four windows were used as ventilation openings. One window in the Living Room (Floor 1, Side A, below Bedroom 3) Den (Floor 1, Side C, below Bedroom 2) and two windows in the Family Room (Side C) were opened sequentially immediately after the door was opened, providing more than eight times the ventilation area as in Experiment 2 (door only).

Figure 4. Ventilation Openings in the Two-Story House

In both Experiment 2 (door only) and Experiment 15 (door and four windows), increased ventilation resulted in transition to a fully developed fire in the compartment of origin. Flames were seen from the family room windows in Experiment 15 (see Figure 5). However, in Experiment 2, no flames were visible on the exterior (due to the distance between the fire compartment and ventilation opening) and a bi-directional air track developed at the door on Side A (smoke out the top and air in the bottom). In Experiment 15, a bi-directional air track is visible at all ventilation openings, with flames visible from the windows in the family room on Side C. No flames extended out the ventilation openings on Side A or from the Den on Side C (see Figure 5). The upper layer is extremely deep (particularly considering the ceiling height of 16’ in the family room and foyer atrium. The velocity of smoke discharge from ventilation openings is moderate.

Figure 5. Fire Conditions at 780 seconds (13:00)

As illustrated in Figure 6, increased ventilation resulted in a increase in heat release rate and subsequent increase in temperature. It is important to note that the peak temperature in Experiment 15 (door and four windows) is approximately 50% higher than in Experiment 2 (door only).

Figure 6. Living Room Temperature 0.30 m(1’) Above the Floor One-Story House

Note. Adapted from Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction (p. 299), by Steven Kerber, 2011, Northbrook, IL: Underwriters Laboratories.

Another Consideration

Comparison of these experiments answers the questions if increased horizontal ventilation would 1) return the fire to a fuel controlled state or 2) improve interior conditions. In a word, no, increased horizontal ventilation without concurrent fire control simply increased the heat release rate (sufficient for the fire to transition through flashover to a fully developed stage) in the involved compartment.

Examining thermal conditions in other areas of the building also provides an interesting perspective on these two sets of experiments. Figure 7 illustrates temperatures at 0.91 m (3’) during Experiment 1 (door only) and Experiment 14 (door and four windows) in the one-story house.

Figure 7. Temperatures at 0.91 m (3’) during Experiments 1 and 14

Note. Adapted from Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction (p. 99, p. 162), by Steven Kerber, 2011, Northbrook, IL: Underwriters Laboratories.

Thermal conditions not only worsened in the fire compartment, but also along the flow path (for a more detailed discussion of flow path, see UL Tactical Implications Part 7) and in downstream compartments. Temperature in the hallway increased from a peak of just over 200o C to approximately 900o C when ventilation was increased by opening the four additional windows.

Unplanned Ventilation

Each of the experiments in this study were designed to examine the impact of tactical ventilation when building ventilation was limited to normal leakage and fire conditions are ventilation controlled (decay stage). In each of these experiments, increased ventilation resulted in a rapid increase in heat release rate and temperature. Even when ventilation was increased substantially (as in Experiments 14 and 15), it was not possible to return the fire to a fuel controlled burning regime.

It is also possible that a door or window will be left open by an exiting occupant or that the fire may cause window glazing to fail. The impact of these types of unplanned ventilation will have an effect on fire development. Creation of an opening prior to the fire reaching a ventilation controlled burning regime will potentially slow fire progression. However, on the flip side, providing an increased oxygen supply will allow the fire to continue to grow, potentially reaching a heat release rate that will result in flashover. If the opening is created after the fire is ventilation controlled, the results would be similar to those observed in each of these experiments. When the fire is ventilation controlled, increased ventilation results in a significant and dramatic increase in heat release rate and worsening of thermal conditions inside the building.

If the fire has self-ventilated or an opening has been created by an exiting occupant, the increased ventilation provided by creating further openings without concurrent fire control will result in a higher heat release rate than if the openings were not present and will likely result in rapid fire progression.

What’s Next?

I will be at UL the week after next and my next post will provide an update on UL’s latest research project examining the influence of vertical ventilation on fire behavior in legacy and contemporary residential construction.

Two tactical implications from the horizontal ventilation study remain to be examined in this series of posts: the impact of closed doors on tenability and the interesting question can you push fire with stream from a hoseline?

The last year has presented a challenge to maintaining frequency of posts to the CFBT Blog. However, I am renewing my commitment to post regularly and will be bringing back Reading the Fire, continuing examination of fundamental scientific concepts, and integration of fire control and ventilation tactics.

References

Kerber, S. (2011). Impact of ventilation on fire behavior in legacy and contemporary residential construction. Retrieved July 16, 2011 from http://www.ul.com/global/documents/offerings/industries/buildingmaterials/fireservice/ventilation/DHS%202008%20Grant%20Report%20Final.pdf

Influence of Ventilation in Residential Structures:
Tactical Implications Part 6

Monday, October 3rd, 2011

The sixth tactical implication identified in the Underwriters Laboratories study of the Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction (Kerber, 2011) identifies potential hazards and risks related to the tactic of Vent Enter Search (VES).

Kerber (2011) provides a straightforward explanation of this tactic.

It can be described as ventilating a window, entering through the window, searching that room and exiting out the same window entered…A primary of objective of VES is to close the door of the room ventilated to isolate the flow path…

Origins and Context

While it is difficult to identify or isolate the origins of many fireground tactics, VES has been practiced by FDNY for many years and is described in detail in the Firefighting Procedures Volume 3, Book 4: Ladder Company Operations at Private Dwellings manual (FDNY, 1997). As described in Ladder Company Operations at Private Dwellings, FDNY truck companies are staffed with an officer, apparatus operator, and four firefighters and are divided into two teams; inside team and outside team. While tactics are dependent on the type of structure and fire conditions; VES is performed by the outside team while the inside team works in conjunction with an engine company, supporting fire attack and searching from the interior. In this context, VES is part of a coordinated tactical operation.

It is also important to recognize the impact of changes in the fire environment since the development of this tactic (likely in the 1960s). Changes in the speed of fire development are graphically illustrated in the Underwriters Laboratories (UL) test of fire development with modern and legacy furnishings.

The tremendous fuel load, development of ventilation limited conditions, and rapid transition from tenable to untenable conditions for firefighters following increased ventilation (without initiation of fire control), reduce the time for Firefighters to make entry and control the door when performing VES in the modern fire environment.

Influence on Fire Behavior

The following incident illustrates the rapid changes in conditions that can result during VES operations. This information was originally presented in the post titled Criticism Versus Critical Thinking. This incident involved VES at a residential structure where rapid fire progress required the Captain conducting the search to perform emergency window egress from a second floor window onto a ladder.

Companies were dispatched to a residential fire at 0400 hours with persons reported. On arrival, cars were observed in the driveway and neighbors reported the likely location of a trapped occupant on the second floor.

Given fire conditions on Floor 1, the Captain of the first in truck, a 23 year veteran, determined that Vent, Enter, and Search (VES) was the best option to quickly search and effect a rescue.

The following video clip illustrates conditions encountered at this residential fire:


Find more videos like this on firevideo.net

In his, vententersearch.com post Captain Van Sant provided the following information about his observations and actions:

When we vent[ed] the window with the ladder, it looks like the room is burning, but the flames you see are coming from the hallway, and entering through the top of the bedroom doorway. Watch it again and you’ll see the fire keeps rolling in and across the ceiling.

When I get to the window sill, the queen-sized bed is directly against the window wall, so there is no way to “check the floor” … Notice that you continue to see my feet going in, because I’m on the bed.

Believe me, in the beginning, this was a tenable room both for me and for any victim that would have been in there…

My goal was to get to the door and close it, just like VES is supposed to be done. We do it successfully all the time.

When I reached the other side of the bed, I dropped to the floor and began trying to close the door. Unfortunately, due to debris on the floor, the door would not close [emphasis added].

Conditions were still quite tenable at this point, but I knew with the amount of fire entering at the upper level, and smoke conditions changing, things were going to go south fast…

I kept my eyes on my exit point, and finished my search, including the closet, which had no doors on it. Just as I was a few feet from the window, the room lit off…

Tactical Considerations

Is VES an appropriate tactic for primary search in private dwellings? This question must be placed into operational context bounded by fire dynamics, resources and staffing, experience level of the firefighters involved, potential for survivable occupants, and the fireground risk management philosophy of the department. Consider the following:

  • There have been instances where VES has resulted in saving of civilian life.
  • There have been instances where VES has resulted in significant thermal injury to firefighters.
  • The UL ventilation tests (Kerber, 2011) demonstrate that conditions rapidly become untenable for civilian occupants in rooms with open doors. Rooms with closed doors remain tenable for civilian occupants for a considerable time.
  • VES may result in rapid search of specific threatened areas.
  • VES is a high risk tactic that involves working alone (but if a second firefighter remains at the entry point this is similar to oriented search).
  • VES (as normally practiced) involves working without a hoseline.
  • VES changes the ventilation profile and places firefighters in the flow path between the fire and an exhaust opening (unless or until the door to the compartment is closed)
  • As demonstrated in the UL ventilation tests (Kerber, 2011), thermal conditions change from a tenable operating environment for firefighters to untenable and life threatening in a matter of seconds.

Based on these factors, you may determine that VES is not an appropriate tactic for primary search under any circumstances, or you may determine that it might be appropriate under specific circumstances. The following tactical scenarios may provide a framework for discussion of these issues.

Scenario 1:You have responded to a fire in a medium sized, two-story, wood frame, single-family dwelling at 02:13 hours. You observe a smoke issuing at moderate velocity from the eaves and condensed pyrolizate on the inside of window glazing. A dull reddish glow can be observed through several adjacent windows on the Charlie Side (back of the house), Floor 1.

Given your normal first alarm assignment and staffing Is VES an appropriate option for primary search given the conditions described and potential for possible occupants? Why or why not?

Scenario 2: You have the same building, smoke, air track, heat, and flame indicators as in Scenario 1, but a female occupant meets you on arrival and reports that her husband is trying to rescue their daughter who was sleeping in a bedroom on Floor 2 at the Alpha/Bravo corner of the house.

Given your normal first alarm assignment and staffing Is VES an appropriate option for primary search given the conditions described and reported occupants?  Why or why not?

Scenario 3: You have the same building, smoke, air track, heat, and flame indicators as in Scenario 1, and observe two occupants, an adult male and a female child in a window on Floor 2 at the Alpha/Bravo corner of the house. Smoke at low velocity is issuing from the open window above the occupants. However, before you can raise a ladder to rescue the occupants in the window, they disappear from view and the volume and velocity of smoke discharge from the window increases.

Given your normal first alarm assignment and staffing Is VES an appropriate option for primary search given the conditions described and initial observation of occupants? Why or why not?

Vertical Ventilation Study

UL has commenced a study on the Effectiveness of Vertical Ventilation and Fire Suppression Tactics using the same legacy and contemporary residential structures used in their study of horizontal ventilation. This research project will examine a range of vertical ventilation variables including the size, location, and timing of openings. In addition, further research will be conducted on the effectiveness of exterior streams and their impact on interior conditions.

Preliminary design parameters for the study were developed in conjunction with a technical panel representing a wide range of jurisdictions and types of fire service agencies, including:

  • Atlanta Fire Department (GA)
  • Central Whidbey Island Fire & Rescue (WA)
  • Chicago Fire Department (IL)
  • Cleveland Fire Department (OH)
  • Coronado Fire Department (CA)
  • Fire Department of the City of New York (FDNY) (NY)
  • Loveland-Symmes Fire Department (OH)
  • National Institute of Standards and Technology (NIST) (MD)
  • Northbrook Fire Department (IL)
  • Milwaukee Fire Department (WI)
  • Lake Forest Fire Department (IL)
  • Phoenix Fire Department (AZ)

Full scale tests are anticipated to begin in January 2012. I will provide updates as this research project progresses.

References

Fire Department of the City of New York (FDNY). (1997) Firefighting prodedures volume 3 book 4: Ladder company operations at private dwellings. New York: Author.

Kerber, S. (2011). Impact of ventilation on fire behavior in legacy and contemporary residential construction. Retrieved July 16, 2011 from http://www.ul.com/global/documents/offerings/industries/buildingmaterials/fireservice/ventilation/DHS%202008%20Grant%20Report%20Final.pdf

Influence of Ventilation in Residential Structures: Tactical Implications Part 5

Thursday, September 8th, 2011

The fifth tactical implication identified in the Underwriters Laboratories study of the Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction (Kerber, 2011) is described as failure of the smoke layer to lift following horizontal natural ventilation and smoke tunneling and rapid air movement in through the front door.

In the experiments conducted by UL, both the single and two story dwellings filled rapidly with smoke with the smoke layer reaching the floor prior to ventilation. This resulted in zero visibility throughout the interior (with the exception of the one bedroom with a closed door). After ventilation, the smoke layer did not lift (as many firefighters might anticipate) as the rapid inward movement of air simply produced a tunnel of clear space just inside the doorway.

Put in the context of the Building, Smoke, Air Track, Heat, and Flame (B-SAHF) fire behavior indicators, these phenomena fit in the categories of smoke and air track. Why did these phenomena occur and what can firefighters infer based on observation of these fire behavior indicators?

Smoke Versus Air Track

There are a number of interrelationships between Smoke and Air Track. However, in the B-SAHF organizing scheme they are considered separately. As we begin to develop or refine the map of Smoke Indicators it is useful to revisit the difference between these two categories in the B-SAHF scheme.

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

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

Smoke Indicators

There are a number of smoke characteristics and observations that provide important indications of current and potential fire behavior. These include:

  • Location: Where can you see smoke (exterior and interior)?
  • Optical Density (Thickness): How dense is the smoke? Can you see through it? Does it appear to have texture like velvet (indicating high particulate content)?
  • Color: What color is the smoke? Don’t read too much into this, but consider color in context with the other indicators.
  • Physical Density (Buoyancy): Is the smoke rising, sinking, or staying at the same level?
  • Thickness of the Upper Layer: How thick is the upper layer (distance from the ceiling to the bottom of the hot gas layer)?

As discussed in Reading the Fire: Smoke Indicators Part 2, these indicators can be displayed in a concept map to show greater detail and their interrelationships (Figure 1).

Figure 1. Smoke Indicators Concept Map

Air Track

Air track includes factors related to the movement of smoke out of the compartment or building and the movement of air into the fire. Air track is caused by pressure differentials inside and outside the compartment and by gravity current (differences in density between the hot smoke and cooler air). Air track indicators include velocity, turbulence, direction, and movement of the hot gas layer.

  • Direction: What direction is the smoke and air moving at specific openings? Is it moving in, out, both directions (bi-directional), or is it pulsing in and out?
  • Wind: What is the wind direction and velocity? Wind is a critical indicator as it can mask other smoke and air track indicators as well as serving as a potentially hazardous influence on fire behavior (particularly when the fire is in a ventilation controlled burning regime).
  • Velocity & Flow: High velocity, turbulent smoke discharge is indicative of high temperature. However, it is essential to consider the size of the opening as velocity is determined by the area of the discharge opening and the pressure. Velocity of air is also an important indicator. Under ventilation controlled conditions, rapid intake of air will be followed by a significant increase in heat release rate.

As discussed in Reading the Fire: Air Track Indicators Part 2, these indicators can be displayed in a concept map to show greater detail and their interrelationships (Figure 2).

Figure 2. Air Track Indicators Concept Map

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Discharge of smoke at openings and potential openings (Building Factors) is likely the most obvious indicator of air track while lack of smoke discharge may be a less obvious, but equally important sign of inward movement of air. Observation and interpretation of smoke and air movement at openings is an essential part of air track assessment, but it must not stop there. Movement of smoke and air on the interior can also provide important information regarding fire behavior.

An Ongoing Process

Reading the fire is an ongoing process, beginning with reading the buildings in your response area prior to the incident and continuing throughout firefighting operations. It is essential to not only recognize key indicators, but to also note changing conditions. This can be difficult when firefighters and officer are focused on the task at hand.

UL Experiment 13

This experiment examined the impact of horizontal ventilation through the door on Side A and one window as high as possible on Side C near the seat of the fire. The family room was the fire compartment. This room had a high (two-story) ceiling with windows at ground level and the second floor level (see Figure 3).

Figure 3. Two-Story Dwelling

In this experiment, the fire was allowed to progress for 10:00 after ignition, at which point the front door (see Figure 3) was opened to simulate firefighters making entry. Fifteen seconds after the front door was opened (10:15), an upper window in the family room (see Figure 3) was opened. No suppression action was taken until 12:28, at which point a 10 second application of water was made through the window on Side C using a straight stream from a combination nozzle.

As with all the other experiments in this series fire development followed a consistent path. The fire quickly consumed much of the available oxygen inside the building and became ventilation controlled. At oxygen concentration was reduced, heat release rate and temperature within the building also dropped. Concurrently, smoke and air track indicators visible from the exterior were diminished. Just prior to opening the door on Side A, there was little visible smoke from the structure (see Figure 4).

Figure 4. Experiment 13 at 00:09:56 (Prior to Ventilation)

As illustrated in Figure 5, a bi-directional air track was created when the front door was opened. Hot smoke flowed out the upper area of the doorway while air pushed in the bottom creating a tunnel of clear space inside the doorway (but no generalized lifting of the upper layer.

Figure 5. Experiment 13 at 00:10:14 (Door Open)

As illustrated in Figure 6, opening the upper level window in the family room resulted in a unidirectional air track flowing from the front door to the upper level window in the family room. No significant exhaust of smoke can be seen at the front door, while a large volume of smoke is exiting the window. However, while the tunneling effect at floor level was more pronounced (visibility extended from the front door to the family room), there was no generalized lifting of the upper layer throughout the remainder of the building.

Figure 6. Experiment 13 at 00:10:21 (Door and Window Open)

With the increased air flow provided by ventilation through the door on Side A and Window at the upper level on Side C, the fire quickly transitioned to a fully developed stage in the family room. The heat release rate (HRR) and smoke production quickly exceeded the limited ventilation provided by these two openings and the air track at the front door returned to bi-directional (smoke out at the upper level and air in at the lower level) as shown in Figure 7.

Figure 7. Experiment 13 at 00:11:22 (Door and Window Open)

What is the significance of this observation? Movement of smoke out the door (likely the entry point for firefighters entering for fire attack, search, and other interior operations) points to significant potential for flame spread through the upper layer towards this opening. The temperature of the upper layer is hot, but flame temperature is even higher, increasing the radiant heat flux (transfer) to crews working below. Flame spread towards the entry point also has the potential to trap, and injure firefighters working inside.

Gas Velocity and Air Track

A great deal can be learned by examining both the visual indicators illustrated in Figures 4-7 and measurements taken of gas velocity at the front door. During the ventilation experiments conducted by UL, gas velocities were measured at the front door and at the window used for ventilation (see Figure 3). Five bidirectional probes were placed in the doorway at 0.33 m (1’) intervals. Positive values show gas movement out of the building while negative values show inward gas movement. In order to provide a simplified view of gas movement at the doorway, Figure 8 illustrates gas velocity 0.33 m (1’) below the top of the door, 0.33 m (1’) from the bottom of the door, and 0.66 m (2’) above the bottom of the door.

A bidirectional (out at the top and in at the bottom) air track developed at the doorway before the door was opened (see Figure 8) as a result of leakage at this opening. It is interesting to note variations in the velocity of inward movement of air from the exterior of the building, likely a result of changes in combustion as the fire became ventilation controlled. The outward flow at the upper level resulted in visible smoke on the exterior of the building. While not visible, inward movement of air was also occurring (as shown by measurement of gas velocity at lower levels in the doorway.

Creation of the initial ventilation opening by opening the front door created a strong bidirectional air track with smoke pushing out the top of the door while air rapidly moved in the bottom. Had the door remained the only ventilation opening, this bidirectional flow would have been sustained (as it was in all experiments where the door was the only ventilation opening).

Opening the upper window in the family room resulted in a unidirectional flow inward through the doorway. However, this phenomenon was short lived, with the bidirectional flow reoccurring in less than 60 seconds. This change in air track resulted from increased heat release rate as additional air supply was provided to the fire in the family room.

Figure 8. Front Door Velocities

Note: Adapted from Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction (p. 243), by Stephen Kerber, Northbrook, IL: Underwriters Laboratories, 2011.

While not the central focus of the UL research, these experiments also examined the effects of exterior fire stream application on fire conditions and tenability. Each experiment included a 10 second application with a straight stream and a 10 second application of a 30o fog pattern. Between these two applications, fire growth was allowed to resume for approximately 60 seconds.

The straight stream application resulted in a reduction of temperature in the fire compartment and adjacent compartments (where there was an opening to the family room or hallway) as water applied through the upper window on Side C (ventilation opening) cooled the compartment linings (ceiling and opposite wall) and water deflected off the ceiling dropped onto the burning fuel. As the stream was applied, air track at the door on Side A changed from bidirectional to unidirectional (inward). This is likely due to the reduction of heat release rate achieved by application of water onto the burning fuel with limited steam production.

When the fog pattern was applied, there was also a reduction of temperature in the fire compartment and adjacent compartments (where there was an opening in the family room or hallway) as water was applied through the upper window on Side C (ventilation opening) cooled the upper layer, compartment linings, and water deflected off the ceiling dropped onto the burning fuel. The only interconnected area that showed a brief increase in temperature was the ceiling level in the dining room. However, lower levels in this room showed an appreciable drop in temperature. Air track at the door on Side A changed from bidirectional to unidirectional (outward) when the fog stream was applied. This effect is likely due to air movement inward at the window on Side C and the larger volume of steam produced on contact with compartment linings as a result of the larger surface area of the fog stream.

The effect of exterior streams will be examined in more detail in a subsequent post.

Important Lessons

The fifth tactical implication identified in the Underwriters Laboratories study of the Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction (Kerber, 2011) is described as failure of the smoke layer to lift following horizontal natural ventilation and smoke tunneling and rapid air movement in through the front door.

Additional lessons that can be learned from this experiment include:

  • Ventilating horizontally at a high point results in higher flow of both air and smoke.
  • Increased inward air flow results in a rapid increase in heat release rate.
  • The rate of fire growth quickly outpaced the capability of the desired exhaust opening, returning the intended inlet to a bi-directional air track (potentially placing firefighters entering for fire attack or search at risk due to rapid fire spread towards their entry point).

Tactical applications of this information include:

  • Ensure that the attack team is in place with a charged line and ready to (or has already) attack the fire (not simply ready to enter the building) before initiating horizontal ventilation.
  • Cool the upper layer any time that it is above 100o C (212o F) to reduce radiant and convective heat flux and to limit potential for ignition and flaming combustion in the upper layer.

Note that this research project did not examine the impact of gas cooling, but examination of the temperatures at the upper levels in this experiment (and others in this series) point to the need to cool hot gases overhead.

What’s Next?

I am on the hunt for videos that will allow readers to apply the tactical implications of the UL study that have been examined to this point in conjunction with the B-SAHF fire behavior indicators. My next post will likely provide an expanded series of exercises in Reading the Fire.

The next tactical implication identified in the UL study (Kerber, 2011) examines the hazards encountered during Vent Enter Search (VES) tactical operations. A subsequent post will examine this tactic in some detail and explore this tactical implication in greater depth.

References

Kerber, S. (2011). Impact of ventilation on fire behavior in legacy and contemporary residential construction. Retrieved July 16, 2011 from http://www.ul.com/global/documents/offerings/industries/buildingmaterials/fireservice/ventilation/DHS%202008%20Grant%20Report%20Final.pdf

Influence of Ventilation in Residential Structures: Tactical Implications Part 4

Sunday, August 14th, 2011

The fourth tactical implication identified in the Underwriters Laboratories study of the Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction (Kerber, 2011) is that fire attack and (tactical) ventilation must be coordinated. This recommendation has been repeated in National Institute for Occupational Safety and Health (NIOSH) Death in the Line of Duty Reports for many years. In fact, most reports on firefighter fatalities related to rapid fire progression contain this recommendation.

Importance of Coordination

Coordination of (tactical) ventilation and fire attack as a tactical implication is closely related to the first two tactical implications identified in the UL study; potential changes in fire behavior based on stages of fire development, burning regime, and changes in ventilation profile that increase oxygen supplied to the fire.

If air is added to the fire and water is not applied in the appropriate time frame the fire gets larger and the hazards to firefighters increase. Examining the times to untenability provides the best case scenario of how coordinated the attack needs to be. Taking the average time for every experiment from the time of ventilation to the time of the onset of firefighter untenability conditions yields 100 seconds for the one-story house and 200 seconds for the two-story house. In many of the experiments from the onset of firefighter untenability until flashover was less than 10 seconds. These times should be treated as very conservative. If a vent location already exists because the homeowner left a window or door open then the fire is going to respond faster to additional ventilation openings because the temperatures in the house are going to be higher at the time of the additional openings (Kerber, 2011, p. 289-290)

The Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction Underwriters Laboratories (UL) on-line course and report provide an example of firefighters are at risk when ventilation is performed prior to entry, fire attack is delayed, and other tactical operations such as primary search are initiated.

In UL’s hypothetical example, the firefighters make entry into the one-story house, search the living room (fire compartment), the kitchen, and dining room shortly after forcing the door and ventilating a large window in the fire compartment. Consider a somewhat different scenario, with the same fire conditions.

Companies respond to a residential fire with persons reported during the early morning hours. A truck and engine arrive almost simultaneously and while the engine lays a supply line from a nearby hydrant, the truck company forces entry, ventilates a window on Side A, and begins primary search (anticipating that the engine crew will be right behind them to attack the fire). The engine completes a forward lay and begins to stretch an attack line after the search team has made entry.

Figure 1. Timeline and Progression of Primary Search

Figure 2. View of the Living Room (Fire Compartment) from the Door on Side A

As illustrated in Figure 3, visible flaming combustion when the door is opened at 08:00 is limited to a small flame from the top of the couch just inside the door on Side A. However, in the 30 seconds that it takes for the search team to make entry, flaming combustion has resumed and flames are near or at the ceiling above the couch. The search team may estimate that they have time to complete a quick search of the bedrooms (likely location of the reported persons). However, fire development progresses to untenable conditions within a minute, trapping the crew on Side D of the house.

Figure 3. Fire Progression in the Living Room 00:08:00 to 00:10:00

As the search team completes primary search of Bedroom 2 and moves towards Bedroom 3 in the hallway, conditions have deteriorated to an untenable level. Figure 4 illustrates the change in temperature at the 3’ level in the Living Room (fire compartment). Shortly before the search team reached Bedroom 2, fire conditions in the living room began to change dramatically, with temperature at the 3’ level transitioning from ordinary to extreme, quickly becoming untenable in the living room, hallway and adjacent compartments. In addition to this significant change in temperature, flames (with temperatures higher than the gas temperature at the 3’ level) significantly increase radiant heat transfer (flux) to the surface of both fuel packages and firefighters protective equipment.

Figure 4. Temperature at the 3’ Level

Note: Figure 4 illustrates temperature conditions starting eight minutes after ignition. The fire previously progressed through incipient and growth stages before beginning to decay due to lack of ventilation.

Why the Dramatic Change in Conditions?

As discussed in UL Tactical Implications Part 1, Fires in the contemporary environment progress from ignition and incipient stage to growth, but often become ventilation controlled and begin to decay, rather than continuing to grow into a fully developed fire. This ventilation induced decay continues until the ventilation profile changes (e.g., window failure due to fire effects, opening a door for entry or egress, or intentional creation of ventilation openings by firefighters. When ventilation is increased, heat release rate again rises and temperature climbs with the fire potentially transitioning through flashover to the fully developed stage (see Figure 4 and 5).

Figure 5. Fire Development in a Compartment

Captain James Mendoza of the San Jose (CA) Fire Department and CFBT-US Lead Instructor demonstrates the influence of ventilation on fire development using a small scale prop developed by Dr. Stefan Svensson of the Swedish Civil Contingencies Agency.

The prop used in this demonstration is a small, single compartment with a limited ventilation opening on the right side (which in a full size building could be represented by normal building leakage or a compartment opening that is restricted such as a partially open door or window). The front wall of the prop is ceramic glass to permit direct observation of fire conditions within the compartment.

As you watch this demonstration, pay particular attention to how conditions change as the fire develops and then enters the decay stage. In addition, observe how quickly the fire returns to the growth stage and develops conditions that would be untenable after the window is opened at 12:17.

Download Doll’s House Plans (or Doll’s House Plans: Metric) for directions on how to construct a similar small scale prop.

Fire development and changes in conditions following ventilation in this demonstration mirror those seen in the full scale experiments conducted by UL. Increasing ventilation to a ventilation controlled fire, results in increased heat release rate and transition from decay to the growth stage of fire development.

The same phenomena can be observed under fireground conditions in the following video clip of a residential fire in Dolton, Illinois (this is a long video, watch the first several minutes to observe the changes in fire behavior).

It appears that the front door was open at the start of the video clip and the large picture window on Side A was ventilated at approximately 00:47. Fire conditions quickly transition to the growth stage with flames exiting the window and door, causing firefighters on an uncharged hoseline that had been advanced into Floor 1, to quickly withdraw.

As discussed in UL Tactical Implications: Part 1:

  • Fires that have progressed beyond the incipient stage are likely to be ventilation controlled when the fire department arrives.
  • Ventilation controlled fires may be in the growth, decay, or fully developed stage.
  • Regardless of the stage of fire development, when a fire is ventilation controlled, increased ventilation will always result in increased HRR.
  • Firefighters and fire officers must recognize that the ventilation profile can change (e.g., increasing ventilation) as a result of tactical action or fire effects on the building (e.g., window failure).
  • Firefighters and fire officers must anticipate potential changes in fire behavior related to changes in the ventilation profile and ensure that fire attack and ventilation are closely coordinated.

Coordinated Tactical Operations

Understanding how fire behavior can be influenced by changes in ventilation is essential. But how can firefighters put this knowledge to use on the fireground and what exactly does coordination of tactical ventilation and fire attack really mean?

Tactical ventilation can be defined as the planned, systematic, and coordinated removal of hot smoke and fire gases and their replacement with fresh air. Each of the elements of this definition is important to safe and effective tactical operations.

Ventilation (both tactical and unplanned) not only removes hot smoke, but it also introduces fresh air which can have a significant effect on fire behavior.

Tactical ventilation must be planned; these two elements speak to the intentional nature of tactical ventilation. Tactics to change the ventilation profile must be intended to influence the fire environment or fire behavior in some way (e.g., raise the level of the upper layer to increase visibility and tenability). The ventilation plan must also consider the flow path (e.g., vent ahead of, not behind, the attack team; vent in the immediate area of the fire, not at a remote location).

Tactical ventilation must be systematic, exhaust openings should generally be made before inlet openings (particularly when working with positive pressure ventilation or when taking advantage of wind effects).

And as pointed out in the UL Study (Kerber, 2011), tactical ventilation must be coordinated. Coordination of ventilation and other tactical operations requires consideration of sequence and timing:

Sequence: Ventilation may be completed before, during, or after fire attack has been initiated. Sequence will likely depend on the stage of fire development, burning regime, time required to reach the fire.

If the fire is small and staffing is limited, it may be appropriate to control the fire and then effect ventilation (e.g., hydraulic ventilation performed by the attack team). This approach minimizes potential fire growth,

In general, when the fire is ventilation controlled (as those beyond the incipient stage are likely to be), ventilation should not be completed unless the attack line(s) can quickly apply water to the seat of the fire. In a small, single family dwelling this may mean that the attack team is on-air, the line is charged, and the entry door is unlocked or has been forced and is being controlled (held closed). In a larger building, this may mean that the attack line has entered the structure and is in position to move onto the fire floor or into the fire area.

The key questions that must be answered prior to implementing tactical ventilation are:

  1. What influence will these ventilation tactics have on fire behavior?
  2. Are charged and staffed attack line(s) in place?
  3. Will the attack team(s) be able to quickly reach the fire?
  4. How will this impact crews operating on the interior of the building?

Coordination requires clear, direct communication between companies or crews assigned to ventilation, fire attack, and other tactical functions that are or will be taking place inside the building.

Important: While not a tactical implication directly raised by the UL study, another important consideration is the hazard of working without or ahead of the hoseline. While a controversial topic in the US fire service (where truck company personnel generally work on the interior without a hoseline), searching with a hoseline provides a means of protection and a defined exit path. Staffing is another key element of the operational context. If you do not have enough personnel to control the fire and search; in most cases it is likely the best course of action to control the fire and ensure a safer operating environment for search operations.

What’s Next?

The next tactical implication identified in the UL study (Kerber, 2011) examines information that may be obtained by reading the air track at the entry point opening. This implication will be expanded with a broader discussion of air track indicators and how related hazards can be mitigated to improve firefighter safety.

References

Kerber, S. (2011). Impact of ventilation on fire behavior in legacy and contemporary residential construction. Retrieved July 16, 2011 from http://www.ul.com/global/documents/offerings/industries/buildingmaterials/fireservice/ventilation/DHS%202008%20Grant%20Report%20Final.pdf

 

Note: Figure 4 illustrates temperature conditions starting eight minutes after ignition. The fire previously progressed through incipient and growth stages before beginning to decay due to lack of ventilation.

Why the Dramatic Change in Conditions?

As discussed in UL Tactical Implications Part 1 [LINK], Fires in the contemporary environment progress from ignition and incipient stage to growth, but often become ventilation controlled and begin to decay, rather than continuing to grow into a fully developed fire. This ventilation induced decay continues until the ventilation profile changes (e.g., window failure due to fire effects, opening a door for entry or egress, or intentional creation of ventilation openings by firefighters. When ventilation is increased, heat release rate again rises and temperature climbs with the fire potentially transitioning through flashover to the fully developed stage (see Figure 4 and 5).

Figure 5. Fire Development in a Compartment

Influence of Ventilation in Residential Structures: Tactical Implications Part 3

Sunday, July 17th, 2011

UL’s third tactical implication is that there may be little smoke showing when a fire initially enters the decay stage as a result of limited ventilation. These fire conditions may present similar indicators to an incipient fire. However, fire conditions and the hazards presented to firefighters are considerably different.

Visible Indications of Fire Development

In Reading the Fire: B-SAHF, I introduced Building, Smoke, Air Track, Heat, and Flame (B-SAHF) as an organizing scheme for fire behavior indicators. Use of a standardized and organized approach to reading the fire can improve our ability to assess current fire conditions and predict likely fire development and changes that may occur.

Station Officer Shan Raffel of Queensland (Australia) Fire Rescue recently published an excellent article titled The Art of Reading Fire on the FirefighterNation website that provides another view of the B-SAHF indicators and Reading the Fire.

Building factors (particularly the normal ventilation profile, size and compartmentation, and thermal characteristics) can have a significant impact on fire development and how fire conditions present from the exterior of the building. However, this UL tactical implication relates most closely to Smoke and Air Track as well as somewhat indirectly to Heat (but this is the key to understanding what is happening). First a quick review of these key indicators

Smoke: What does the smoke look like and where is it coming from? This indicator can be extremely useful in determining the location and extent of the fire. Smoke indicators may be visible on the exterior as well as inside the building.

Air Track: Related to smoke, air track is the movement of both smoke (generally out from the fire area) and air (generally in towards the fire area).

Heat: This includes a number of indirect indicators. Heat cannot be observed directly, but you can feel changes in temperature and may observe the effects of heat on the building and its contents. Visual clues such as crazing of glass and visible pyrolysis from fuel that has not yet ignited are also useful heat related indicators. Important: Temperature influences smoke and air track indicators such as volume and velocity of smoke discharge.

For a more detailed look at B-SAHF and reading the fire, see the following posts:

How to Improve Your Skills
Building Factors
Building Factors Part 2
Building Factors Part 3
Smoke Indicators
Smoke Indicators Part 2
Air Track Indicators
Air Track Indicators Part 2
Heat Indicators
Heat Indicators Part 2
Heat Indicators Part 3
Flame Indicators
Flame Indicators Part 2
Incipient Stage Fires: Key Fire Behavior Indicators
Growth Stage Fires: Key Fire Behavior Indicators
Fully Developed Fires: Key Fire Behavior Indicators
Decay Stage Fires: Key Fire Behavior Indicators

Stages of Fire Development, Burning Regime, Smoke, Air Track & Heat

While the “stages of fire” have been described differently in fire service textbooks the phenomenon of fire development is the same. For our purposes, the stages of fire development in a compartment will be described as incipient, growth, fully developed and decay (see Figure 1). Despite dividing fire development into four “stages” the actual process is continuous with “stages” flowing from one to the next. While it may be possible to clearly define these transitions in the laboratory, in the field it is often difficult to tell when one ends and the next begins.

Understanding the stages of fire development is important, but this only provides a limited picture of fire development in a compartment. Conversion of chemical potential energy from fuel depends on availability of adequate oxygen for the combustion reaction to occur. As the ambient air in the compartment provides adequate oxygen, in incipient stage and early growth stage, heat release rate is limited by the chemical and physical characteristics of the fuel. This condition is known as a fuel controlled burning regime. In a compartment fire, combustion occurs in an enclosure where the air available for combustion is limited by 1) the volume of the compartment and 2) ventilation. Ventilation in a compartment fire is limited (particularly if doors and windows are closed and intact), as the fire grows and heat release rate increases, so too does demand for oxygen. When fire growth is limited by the available oxygen, heat release rate is slowed and then diminishes. This condition is known as a ventilation controlled burning regime.

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 existing ventilation. 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 (see Figure 1)

Figure 1. Fire Development Curve (Fuel and Ventilation Controlled Regimes)

Several things happen as a compartment fire develops: Heat release rate increases, smoke production increases, and pressure within the compartment increases proportionally to the absolute temperature. These conditions result in a number of fire behavior indicators that may be visible from the exterior of the building. As a fire moves from the Incipient to the Growth Stage, an increasing volume of smoke may be visible from the exterior (Smoke Indicator) and the velocity of smoke discharge will likely increase (Air Track Indicator and indirect Heat Indicator).

It is a reasonably logical conclusion that a smaller volume of smoke and lower velocity of smoke discharge will be observed in incipient and early growth stage fires and the volume and velocity of smoke discharge will increase as the fire develops. However, what happens when the fire becomes ventilation controlled?

Influence of Ventilation on Residential Fire Behavior

Earlier this year, Underwriters Laboratories (UL) conducted a series of full-scale experiments to determine the influence of ventilation on fire behavior in legacy and contemporary residential construction (see Did You Ever Wonder? and UL Ventilation Course).

These tests were conducted in full-scale one and two-story, wood-frame structures constructed inside the UL laboratory in Northbrook, IL. Fires in the one-story structure were all started in the living room (see Figure 2) and involved typical contents found in a single-family home.

Figure 2: One-Story Structure and Floor Plan

As discussed in UL Tactical Implications Part 1 and Part 2, each of the fires during these tests quickly became ventilation controlled due to the fuel load within the buildings and limited ventilation provided by closed and intact doors and windows.

As each fire developed, the volume of smoke visible from the exterior and velocity of smoke discharge increased. This is consistent with fire development within the structure and increasing heat release rate, temperature, and volume of smoke production from the developing fire. Figure 3 illustrates exterior conditions at 05:05 during Test 5 conducted in the one-story residence.

Figure 3: Conditions at 05:05 (UL Test 5)

Interestingly, as the fire became ventilation controlled (as determined by both measurement of oxygen concentration and the heat release rate in the building), the volume and velocity of smoke discharge decreased to a negligible level as illustrated in Figure 4.

Figure 4: Conditions at 05:34 (UL Test 5)

This change occurred within a matter of 30 seconds! How might this influence firefighters’ perception of fire conditions inside the building if they arrived at 05:34 rather than 05:04? While presenting much the same as an incipient or early growth stage fire, conditions within the building at 05:34 are significantly ventilation controlled and increased ventilation resulted in rapid fire development and transition through flashover to a fully developed fire.

NIST Phoenix Warehouse Tests

In the Hazard of Ventilation Controlled Fires, I discussed a series of tests conducted by the National Institute for Standards and Technology (NIST) at an ordinary constructed warehouse in Phoenix, AZ. These tests were intended to develop information about performance of ordinary constructed buildings related to structural collapse. However, they also provided some interesting information regarding fire behavior.

One of the tests involved a fire in the front section of the warehouse that measured 50’ x 90’ (15.2 m x 27.4 m) with a height of 15’ (4.6 m) to the top of the pitched truss roof. The fuel load for this test included four stacks of 10 wood pallets and the interior finish and combustible structural elements of the building.  All doors and windows were closed at the start of the test.

Figure 5 illustrates a large volume of dark gray to black smoke discharging from the roof of the structure and flames visible from roof ventilators at 03:57. The B-SAHF indicators visible n this photo indicate a significant growth stage fire within this building.

Figure 5. Conditions at 03:57 (NIST Warehouse Test)

However, at 05:31 conditions visible on the exterior are quite different. The color and volume of smoke discharge (Smoke Indicators) as well as the velocity of discharge (Air Track Indicator) may lead firefighters to believe that this is an incipient or early growth stage fire. Nothing could be further from the truth. This fire is in the decay stage as a result of limited ventilation and any increase in ventilation will result in a rapid and significant increase in heat release rate!

Figure 6. Conditions at 05:31 (NIST Warehouse Test)

For more information on these tests see Structural Collapse Fire Tests: Single Story, Ordinary Construction Warehouse (Stroup, Madrzykowski, Walton, & Twilley, 2003) or view the videos of this series of tests at the NIST Structural Collapse webpage.

The Key

Heat release rate and temperature drop as the fire becomes ventilation controlled. Volume and velocity of smoke discharge are a function of pressure (given a constant opening size). Reduction in temperature and corresponding reduction in pressure will result in a smaller volume and lower velocity of smoke discharge.

When the temperature is the same, the velocity of discharge will likely be similar. Figure 1 shows that the temperature inside a compartment may be the same during the growth and decay stages of the fire. If the ventilation profile (number, size, and location of openings) remains the same, similar Smoke and Air Track indicators can be present.

Decay stage incidators may be subtle. Consider the full range of B-SAHF inciators that may be observed under ventilation controlled, decay stage conditions (see Figure 7.

Figure 7. B-SAHF Decay Stage Indicators.

Durango, Colorado Commercial Fire

CFBT-US developed a case study examining an extreme fire behavior event that occurred during a commercial fire in Durango, CO in 2008 injuring nine firefighters and fire officers. The reporting party indicated that there was a large amount of dark smoke coming from the roof of the building. However, when firefighters arrived, they found nothing showing but a small amount of light colored smoke. Why might this have been the case?

Download a copy of the Fire Behavior Case Study: Durango CO Commercial Fire and see if this may have been a result of similar fire development and presentation of fire behavior indicators as seen in the UL and NIST tests!

Ed Hartin, MS, EFO, MIFireE, CFO

References

Kerber, S. (2011). Impact of ventilation on fire behavior in legacy and contemporary residential construction. Retrieved July 16, 2011 from http://www.ul.com/global/documents/offerings/industries/buildingmaterials/fireservice/ventilation/DHS%202008%20Grant%20Report%20Final.pdf.

Stroup, D., Madrzykowski, D., Walton, W., & Twilley, W. (2003). Structural collapse fire tests: Single story, ordinary construction warehouse, NISTIR 6959. Retrieved July 16, 2011 from http://www.nist.gov/customcf/get_pdf.cfm?pub_id=861215

Safe & Effective Live Fire Training or Near Miss?

Monday, July 4th, 2011

A recent video posted on the firevideo.net [http://firecamera.net/] web brought to mind a number of painful lessons learned regarding live fire training in acquired structures. When watching video of fire training or emergency incidents, it is essential to remember that video provides only one view of the events. This video, titled Probationary Live House Burn shows a live fire evolution from ignition through fire attack with the comment “Burnin up the probies… LOL”.

This video shows multiple fire locations and an extremely substantial fire load (well in excess of what is necessary to bring typical residential compartments to flashover). I am uncertain if the comment posted with the video “burnin up the probies…LOL [laughing out loud]” was posted by an instructor or learner. Likely this is considered as just a joke, but comments like this point to our collective cultural challenges in providing safe and effective live fire training.

Fuel Load & Ventilation in Live Fire Training

NFPA 1403 Standard on Live Fire Training is reasonably explicit regarding the nature of acceptable fuel, extent of fuel load, as well as number and location of fires used for live fire training in acquired structures.

4.3.1 The fuels that are utilized in live fire training evolutions shall have known burning characteristics that are as controllable as possible.

4.2.17 Combustible materials, other than those intended for the live fire training evolution, shall be removed or stored in a protected area to preclude accidental ignition.

4.3.3* Pressure-treated wood, rubber, and plastic, and straw or hay treated with pesticides or harmful chemicals shall not be used.

A.4.3.3 Acceptable Class A materials include pine excelsior, wooden pallets, straw, hay, and other ordinary combustibles.

Fuel materials shall be used only in the amounts necessary to create the desired fire size.

A.4.3.4 An excessive fuel load can contribute to conditions that create unusually dangerous fire behavior. This can jeopardize structural stability, egress, and the safety of participants.

4.3.5 The fuel load shall be limited to avoid conditions that could cause an uncontrolled flashover or backdraft.

4.4.15 Only one fire at a time shall be permitted within an acquired structure.

4.4.16 Fires shall not be located in any designated exit paths.

While quite explicit regarding fuel requirements and limitations, NFPA 1403 (2007) has little to say about the ventilation with the exception of a brief mention that roof ventilation openings that are normally closed but may be opened in an emergency are permitted (not required as many believe). However, the Appendix has a much more important statement regarding the importance of ventilation to fire development:

A.4.3.7 The instructor-in-charge is concerned with the safety of participants and the assessment of conditions that can lead to rapid, uncontrolled burning, commonly referred to as flashover. Flashover can trap, injure, and kill fire fighters. Conditions known to be variables affecting the attainment of flashover are as follows:

(1) The heat release characteristics of materials used as primary fuels

(2) The preheating of combustibles

(3) The combustibility of wall and ceiling materials

(4) The room geometry (e.g., ceiling height, openings to rooms [emphasis added])

In addition, the arrangement of the initial materials to be ignited, particularly the proximity to walls and ceilings, and the ventilation openings [emphasis added] are important factors to be considered when assessing the potential fire growth.

The building in this video appeared to have been used for multiple evolutions prior to the one depicted in the video. A number of the windows appeared to be damaged, providing increased ventilation to support combustion. The fuel load of multiple pallets and excelsior or straw (acceptable types of fuel) provided an excess of fuel required to reach flashover in typical residential rooms (which may have been an intended outcome and level of involvement given the transitional attack (defense to offense)). If in fact the sets were in multiple rooms, this would be inconsistent with the provisions of NFPA 1403 limiting acquired structure evolutions to a single fire.

It is essential for those of us who conduct live fire training to remember that most of the provisions of NFPA 1403 (2007) are based on line-of-duty deaths of our brothers and sisters. Safe and effective live fire training requires that instructors be technically competent, well versed in the requirements or relevant regulations and standards, and that individually and organizationally we have an appropriate attitude towards safe and effective learning and the process of passing on the craft of firefighting.

One useful case to focus discussion of these issues is the death of Firefighter/Paramedic Apprentice Rachael Wilson of the Baltimore City Fire Department:

Live Fire Training: Remember Rachael Wilson

Live Fire Training Part 2: Remember Rachael Wilson

NIOSH Death in the Line of Duty F2007-09

Independent Investigation Report: Baltimore City Fire Department Live Fire Training Exercise

Door Entry

At 4:56 in the video, accumulation of a layer of smoke is clearly visible under the porch roof. No comment is made about this by the instructors and no action is taken to mitigate the hazard. At 5:55, flames exiting a broken window to the left of the door ignite the smoke layer just prior to when the attack team opens the door.

Figure 1. Fire Gas Ignition Sequence

It is essential to recognize that smoke is fuel and that ignition of this gas phase fuel overhead results in a rapid and signfiicant increase in radiant heat flux (which is dependent largely on temperature and proximity). Cooling the gases overhead and use of good door entry technique can minimize risk of this thermal insult to firefighters and potential for transition to other types of extreme fire behavior such as flashover.

Fire Streams

This video also shows some interesting aspects of fire stream application. A solid (or straight) stream can be quite effective in making a direct attack on the fire. However, when the fire is shielded, the effectiveness of this type of stream is limited. While limited steam production is often cited as an advantage of solid (and straight) streams, initial application of water through the doorway in this video results in significant steam production and limited effect on the fire. This is likely due to shielding of the burning fuel by interior configuration and compartmentation. Remember than no single type of fire stream is effective for all applications.

Perspective

Consider the question posed in the title of this post: Was this a safe and effective live fire training session or a near miss? I suspect that the learners in the video enjoyed this live fire training session and that the instructors desired to provide a quality learning experience. It is even likely that this evolution was conducted substantively (but likely not completely) in compliance with the provisions of NFPA 1403. Like most training exercises and emergency incidents, it is easy to watch a video and criticize the actions of those involved. I do not question the intent of those involved in this training exercise, but point to some issues that we (all of us) need to consider and reflect on as we go about our work and pass on the craft to subsequent generations of firefighters.

What’s Next?

I am working hard at getting back into a regular rhythm of posting and hope to have a post looking at another of the Tactical Considerations from the UL ventilation study up within the next week.

Ed Hartin, MS, EFO, MIFireE, CFO

References

National Fire Protection Association. (2007). NFPA 1403 Standard on live fire training. Quincy, MA: Author.

National Institute for Occupational Safety and Health (NIOSH). (2002). Death in the line of duty, F2007-09. Retrieved February 19, 2009 from http://www.cdc.gov/niosh/fire/pdfs/face200709.pdf

Shimer, R. (2007) Independent investigation report: Baltimore city fire department live fire training exercise 145 South Calverton Road February 9, 2007. Retrieved February 19, 2009 from http://www.firefighterclosecalls.com/pdf/BaltimoreTrainingLODDFinalReport82307.pdf.

Influence of Ventilation in Residential Structures: Tactical Implications Part 2

Saturday, June 18th, 2011

Is making entry with a hoseline for fire attack, ventilation? Is entering through a doorway when conducting search, ventilation? While many firefighters do not think about ventilation when performing these basic fireground tasks, the answer is a resounding yes!

Making Entry is Ventilation

While the Essentials of Firefighting (IFSTA, 2008) defines ventilation as “the systematic removal of heated air, smoke, and fire gases from a burning building and replacing them with cooler air” [emphasis added] (p. 541), the main focus of most ventilation training is on the exhaust opening. In discussing compartment fire development, the 6th Edition of Essentials (IFSTA, 2008) includes a discussion of the concept of fuel and ventilation controlled burning regimes. In addition, the section of the text addressing the positive effects of ventilation such as reducing potential for flashover and backdraft, Essentials (IFSTA, 2008) cautions that increasing ventilation to ventilation limited fires may result in rapid fire progression. However, these concepts were not included in earlier additions and the connection between openings made for the purpose of ventilation and openings made for other reasons is often overlooked.

Ventilation versus Tactical Ventilation

Despite the definitions given in fire service text that describe ventilation in terms of actions taken by firefighters, ventilation is simply the exchange of the atmosphere inside a building with that which is outside. Normal air exchange between the interior and exterior of a building is expressed as the number of complete air exchanges (by volume) per hour and varies depending on the purpose and function of the space. In residential structures, the air in the building is completely exchanged approximately four times per hour. In commercial and industrial buildings this rate may be significantly higher, depending on use. When firefighters arrive to find smoke issuing from a building, ventilation is occurring and when firefighters open a door to make entry, the ventilation profile changes as ventilation has been increased. Remember:

  • If smoke exits the opening (air is entering somewhere else) ventilation is occurring.
  • If air enters the opening (smoke is exiting somewhere else), ventilation is occurring.
  • If smoke exits and air enters the opening ventilation is occurring.

The entry point is a ventilation opening and if the fire is ventilation controlled, any ventilation opening will increase heat release rate (HRR)!

Ventilation Controlled Fires

As discussed in Influence of Ventilation in Residential Structures: Tactical Implications Part 1 [LINK], compartment fires that have progressed beyond the incipient stage are likely to be ventilation controlled when the fire department arrives. Firefighters and fire officers must recognize the potential for a rapid increase in HRR when additional atmospheric oxygen is provided to ventilation controlled fires. This is particularly important when considering door entry and door control during fire attack, search, and other interior operations. The Underwriters Laboratories (UL) research project Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction (Kerber, 2011) examined fire behavior in a small, single-story, wood frame house and a larger, two-story, wood frame house (see Figures 1 & 2) Figure 1. Single-Story Legacy Dwelling

Figure 2. Two-Story Contemporary Dwelling

Each of the fires in these experiments occurred in the living room (one-story house) or family room (two-story house). While the fuel load was essentially the same, the family room had a much greater volume as it had a common cathedral ceiling with an atrium just inside the front door. Experiments one and two examined fire behavior in each of these structures with the front door being opened at the simulated time of arrival of the fire department. Figure 3 illustrates the changes in temperature during UL Experiment 1 (Single Story-Door as Vent Opening) and Experiment 2 (Two-Story-Door as Vent Opening). Figure 3. Living/Family Room Temperature Curves-Door as Ventilation Opening

As illustrated in Figure 3, temperature conditions changed dramatically and became untenable shortly after the front door was opened. In the one-story experiment (Experiment 1) temperature:

  • Was 180 °C (360 °F) at ventilation (480 s),
  • Exceeded the firefighter tenability threshold of 260 °C (500 °F) at 550 s
  • Reached 600 °C (1110 °F) at 650 s and transitioned through flashover to a fully developed fire in the living room

In the two-story experiment (Experiment 2) temperature:

  • Was 220 °C (430 °F) at ventilation (600 s)
  • Exceeded the firefighter tenability threshold of 260 °C (500 °F) at 680 s
  • Reached 600 °C (1110 °F) at 780 s and transitioned through flashover to a fully developed fire in the family room

When the door is opened the clock is ticking! HRR will increase and the tenability within the fire compartment and adjacent spaces will quickly deteriorate unless water can be applied to control the fire. Keeping the door closed until ready to make entry delays starting the clock. Closing the door after entry (leaving room for passage of your hoseline) slows fire development and buys valuable time to control the fire environment, locate the fire, and achieve fire control.

Just as in the UL experiments on the influence of ventilation in residential structures, heat release rate will increase and fire conditions can change dramatically when a door is opened for access and entry.

In 2008, two firefighters from the Riverdale Volunteer Fire Department in Prince Georges County Maryland recently were surprised by a flashover in a small, single family dwelling. In the first photo, firefighters from Engine 813 and Truck 807 prepare to make entry. Note that the front door is closed, the glass of the slider and windows are darkened, and smoke can be observed in the lower area of the front porch. Six seconds later it appears that the front door has been opened, flames are visible through the sliding glass door, and the volume of smoke in the area of the porch has increased. However, the smoke is not thick (optically dense). Forty eight seconds later, as the crew from Truck 807 makes entry to perform horizontal ventilation the volume of smoke from the front door increases and thickens (becomes more optically dense).

Figure 4. Ventilation Induced Flashover-Door as a Ventilation Opening

Note: Photos by Probationary Firefighter Tony George, PGFD The crew from Engine 813 experienced a burst hoseline, delaying fire attack. Two minutes after the first photo, and shortly after the crew from Truck 807 made entry, flashover occurred. For additional information on this incident, see Situational Awareness is Critical.

Door Control

The issue of door control presents a similar (and related) paradox as ventilation. Ventilation is performed to improve interior tenability and to support fire control, but when presented with a ventilation controlled fire, increased air supply increases HRR and can result in worsening tenability and potential for extreme fire behavior. Firefighters often chock doors open to provide ease of hoseline deployment and an open egress path, but when the fire is ventilation controlled, this (ventilation) opening starts the clock on increased HRR and rapid fire development. It is useful to consider door control in two phases, door entry procedures and control of the door after entry.

Size-Up: Door entry begins with a focused size-up as you approach the building. Assessment of conditions is not only the incident commander or officer’s job. Each member entering the building should perform a personal size-up and predict likely conditions. When making entry, size-up becomes more closely focused on conditions observed at or near the door and includes an assessment of potential forcible entry requirements as well as B-SAHF (Building-Smoke, Air Track, Heat, and Flame) indicators. If available, a thermal imaging camera (TIC) can be useful, but remember that temperature conditions may be masked by the thermal characteristics of the building. If a thermal imaging camera is not available, application of a small amount of water to the door may indicate temperature and the level of the hot gas layer (water will vaporize on contact with a hot door).

Size-up begins as you exit the apparatus and approach the building, but continues at the door and after you make entry!

At the door, pay close attention to air track and heat (door temperature) indicators as these can provide important clues to conditions immediately inside the building!

Prior to Entry: If the door is open, close it. If it is closed, don’t open it until you are ready. If the door is unlocked, control is generally a simple process (see Nozzle Techniques and Hose Handling: Part 3 for detailed discussion of door entry when the door is unlocked).

If the door is locked and must be forced, this adds an element of complexity to the door entry process. In selecting a forcible entry method, consider that the door must remain intact and on its hinges if you are going to maintain control of the air track at the opening.

This is fairly easy with outward opening doors. Inward opening doors present a greater challenge. A section of webbing or rope can be used to control an inward door by placing a cinch hitch around the door knob (see Figure 5). As the the door is forced, it can be pulled closed. However, if the door was not locked with a deadbolt, it may re-latch when pulled closed. Figure 5. Door Control with Web or Utility Rope

Figure 5. Door Control with Webbing or Utility Rope

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Alternately, a Halligan or hook may be used to capture the door and pull it substantially closed after it is forced (see Figure 6).

Figure 6. Door Control with a Tool

If B-SAHF (Building, Smoke, Air Track, Heat, & Flame) indicators point to hazardous conditions on the other side of the door, forcible entry must be integrated with good door entry procedure to control potential hazards. After Entry: The most effective way to control the door after entry and provide ease of egress is to have a firefighter remain at the opening to control the door and feed hose to the hose team working inside (see Figure 7).

Figure 7. Door Control After Entry

Note: The Firefighter maintaining door control would be wearing complete structural firefighting clothing and breathing apparatus (this is simply an illustration of door control with a hoseline in place)!

Unfortunately, many companies do not have sufficient staff to maintain a nozzle team of two and leave another firefighter at the door. In these cases, it may be possible for the standby firefighters (two-out) to control the door for the crew working inside until additional resources are available.

Nozzle Technique & Hose Handling

Prior posts on nozzle technique and hose handling included a series of drills to develop proficiency in critical skills.

Review these nine drills and then extend your proficiency by integrating forcible entry with good door entry procedure by maintaining control of the door.

Drill 10-Door Entry-Forcing Inward Opening Doors: Many doors (particularly interior and exterior residential) open inward. In this situation forcible entry, door control, and nozzle operation must bee closely coordinated. Practicing these techniques under a variety of conditions (e.g., wall locations, compartment sizes) is critical to developing proficiency.

Drill 11-Door Entry-Forcing Outward Opening Doors: Commercial (and some interior residential doors) open outward. While less complex, Firefighters must develop skill in integration of forcible entry, door control, and nozzle technique in this situation as well.

Hose Handling and Nozzle Technique Drills 11 & 12 Instructional Plan

In both of these drills, focus on maintaining control of the door during forcible entry and limit air intake by keeping the door as closed as possible while passing the hoseline as it is advanced.

References

Kerber, S. (2011). Impact of ventilation on fire behavior in legacy and contemporary residential construction. Retrieved January 20, 2011 http://www.ul.com/global/documents/offerings/industries/buildingmaterials/fireservice/ventilation/DHS%202008%20Grant%20Report%20Final.pdf

International Fire Service Training Association (IFSTA). (2008) Essentials of firefighting (6th ed.). Stillwater, OK: Fire Protection Publications.

UL Ventilation Course

Saturday, December 18th, 2010

Impact of Ventilation on Fire Behavior

Earlier this year, Underwriters Laboratories (UL) conducted a series of full-scale experiments to determine the influence of ventilation on fire behavior in legacy and contemporary residential construction (see Did You Ever Wonder?).

UL University recently releases an on-line training program based on this research. Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction is an excellent examination of the influence of ventilation on fire behavior and discussion of the tactical implications of the lessons learned through this research.

Every Firefighter and Fire Officer should complete
this training program within the next 30 days!

Completion of this on-line program could be the most important 90 minutes of training that you complete in the next year! I do not make this statement lightly. Understanding the relationship between ventilation and fire behavior is a critical competency for firefighters and fire officers.

After completing this on-line training program, consider the following questions and discuss them with the firefighters and fire officers you work with:

  • What are the indicators of a ventilation controlled fire?
  • How do your forcible entry and door entry procedures influence fire behavior?
  • How do you (or do you) coordinate fire attack and ventilation? How can tactical coordination be improved in your department?
  • What hazards are presented when performing VES (Vent, Enter, & Search) under ventilation controlled conditions? How can these hazards be mitigated?
  • What influence do closed doors have on the survivability profile (for either civilian occupants or trapped firefighters)?
  • What other lessons can you draw from this important research?

Research Report

In addition to the on-line course, UL has published a comprehensive report on this important research projects: Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction.

Video

You can also download an excellent video illustrating the difference between fuel characteristics and loading in legacy and contemporary residential occupancies. This video is a tremendous tool to illustrate changes in the built environment to both firefighters and civilian audiences.

High Resolution Video

Low Resolution Video

Lima Backdraft

I am still working the report on my staff ride to the site of the 1997 backdraft at Luis Giribaldi Street and 28 de Julio Street in the Victoria section of Lima, Peru and should have it posted within the next week.

Ed Hartin, MS, EFO, MIFireE, CFO