Archive for June, 2013

Jason Sowders recently wrote an post on the Fire Engineering in support 150 gpm (570 lpm) as the minimum flow rate for interior structural firefighting and the use of solid (or if not solid, at least straight) streams for interior fire attack. I commented on-line that many of the conclusions stated in Jason’s post was not supported by scientific evidence or the experience of many of the world’s fire services. Have a look at Jason’s post: Nozzle Selection: Are We Defeating the Enemy? and give some thought to what he has to day. What do you agree with, what do you disagree with, and why?

I commend Jason on presenting his perspective in a public forum. While I don’t agree with many of the things that he has to say, putting ideas in a public space allows discussion and argument (using this term in its most positive sense) to improve our knowledge and understanding. Today more than ever, we have access to a tremendous amount of information via the internet and print publications. Some of this information is correct and some is not. To make things even more complicated, some of it is based on commonly held belief resulting from observation of the world around us, that seems quite logical and some of it is based on science which is sound but may seem to conflict with our practical experience. How do we sort through these statements, claims, and arguments?

• Think about what you know?
• How do you know this?
• What are your assumptions and biases (this may be the most difficult question)?
• What resources are available to help you develop a deeper understanding?

Military Metaphor

Jason begins his post by asserting that warfighting involves precision, well thought out methods of attack and overwhelming force to obliterate the enemy. Both statements have an element of truth, but the military metaphor for structural firefighting while useful in some contexts has significant limitations. Consider the differences between a ground offensive in a war and a special operations mission to capture or kill a terrorist leader. Both have elements of precision and well thought out methods, but the later does not use overwhelming force to obliterate the enemy, but employs the force necessary to accomplish the task while minimizing collateral damage.

Jason states that we are in a war and that fire has already invaded our homes, ready to show itself in a very “hostile” manner. The major fallacy in the use of military action or warfare as a metaphor for firefighting is the tendency to anthropomorphize the fire, ascribing humanlike characteristics such as thought and intent. An uncontrolled fire is not alive, it is not hostile, and it is not trying to kill either firefighters or civilians it is simply a physical and chemical phenomena that presents a hazard to life and property in either the natural or built environment.

Chief Fire Officer Paul Young of the Devon & Somerset Fire & Rescue Service asked two important questions during a presentation at an Institution of Fire Engineers presentation several years ago: Are we participating in an individual struggle with a dangerous enemy? Or are we part of a disciplined, organized, and coordinated attack on an increasingly well understood chemical reaction?

These points do not diminish the hazards presented by the modern fire environment, but frame a fundamental difference in perspective about our work. One is dramatic, exciting, and focused to a greater extent on an emotional response (which is necessary, but not sufficient) and the other recognizes that our work while difficult, physical, and requiring emotional strength, must be based on integration of scientific evidence and experience developed in the field.

Heat Release Rate

Jason asserts that the heat release rate of today’s fuels is catching firefighters off guard and that they need to be treated as highly flammable fuels. While this is true to some extent, the term flammability generally refers to ease of ignition (e.g. flash point of liquids, ignition temperature, etc.) rather than heat of combustion (potential energy) or heat release rate (HRR). Jason’s statement that “heat makes more heat” is nonsense at face value in that heat (thermal energy in transit cannot multiply itself. Chemical potential energy in fuel can be transformed to thermal kinetic energy, but it can neither be created or destroyed (law of conservation of energy). However, if the point is that HRR does not (generally) increase in a linear manner, but frequently increases in an exponential manner, is generally correct.

Understanding the concept of heat release rate is critical to understanding and recognizing the hazards presented in the fire environment as well as the capabilities of water as an extinguishing agent.

Flow Rate

Jason asserts that flow rates below 150 gpm (768 lpm) are inadequate for interior structural firefighting without supporting this argument with specific evidence. While I agree that a 1-3/4” hoseline with a flow rate of 150 gpm (570 lpm) is a reasonable choice for interior structural firefighting, there are many fire service agencies around the world that are quite effective with much lower flow rates. How can this be? Context is critical and it is important to consider building characteristics, fuel loading, and tactical framework. That said, it is interesting that the New South Wales Fire Brigades in Australia (who has similar buildings and fuel loads to those found in North America) typically makes entry to residential fires with a flow rate that is five times lower than 150 gpm (570 lpm). This large fire brigade serving both the city of Sydney and smaller communities is effective in fire control while having a firefighter fatality rate that is considerably lower than the US fire service. This is likely due to a combination of factors, but their typical flow rate and use of 38 mm (1-1/2”) hoselines does not seem to have a negative impact on their fire suppression performance.

Jason provides an example of the effect of reducing line pressure on 200’ a 1-3/4” handline from 170 psi to 130 psi (to reduce nozzle reaction); stating that this would reduce the flow rate from 150 gpm (570 lpm) to 115 gpm (435 lpm) and that this would be “woefully inadequate and not a safe practice” as you would be simply containing the fire, not extinguishing it.

The first part of this argument has an element of truth. Reducing the line pressure on a handline reduces flow rate. However, depending on the type of nozzle, there may be other impacts as well. An automatic nozzle will maintain its design pressure with reduced flow rate (as long as the flow is within the nozzle’s flow range). If the nozzle is a standard combination nozzle with a designed nozzle pressure of 100 psi (689 kPa) as evidenced by the original 170 psi (1172 kPa) nozzle pressure in this example, reducing the line pressure not only reduces flow rate, but also increases droplet size and velocity of the stream; which further degrades performance. However, this leaves the question of what flow rate is “adequate” for structural firefighting. As with most questions, the answer is it depends.

Before starting a discussion of the adequacy of given flow rates, it is important to provide a bit of context (as this is not a debate just for the sake of argument, it is important for us to understand not only what we do, but why we do it).

Jason states that a flow rate of 115 gpm (435 lpm) will is inadequate and unsafe and that it will only contain the fire and not extinguish it (without stating fire conditions). Consider the cooling capacity of 115 gpm (435 lpm); this flow rate has a theoretical cooling capacity of 18.87 MW (7.26 kg/s x 2.6 MJ/kg = 18.87 MW). Given that this cooling capacity cannot be achieved in a practical sense it may be reasonable to say that the efficiency of hand held fire streams varies considerably, but as a point of illustration, consider an efficiency of 50% (half of the water is vaporized to steam). In this case, the cooling capacity of 115 gpm (435 lpm)  would be 9.43 MW. As a point of comparison, tests of a fully furnished modern living room conducted by Underwriters Laboratories resulted in a heat release rate of slightly less than 9 MW (Kerber, 2012) and could be readily controlled and extinguished with a flow rate lower than 150 gpm (570 lpm).

I have no argument with establishing a minimum flow rate for 1-3//4” handlines (and actually use 150 gpm as the standard for the agency where I serve as Fire Chief). However, not all fires require 150 gpm (768 lpm) and in other cases 150 gpm (570 lpm) is inadequate. Safety is not driven by flow rate, but by appropriate or inappropriate use of a given flow rate depending on conditions. At a minimum, the flow must at least meet the critical flow rate (minimum to extinguish the fire) and more likely should be somewhat higher to reduce the time to extinguishment. Drastically exceeding the critical flow rate has considerably less impact on time to achieve extinguishment, but has a significant impact on the total volume of water used (which in rural contexts can be limited and in any context results in unnecessary fire control damage). If this resulted in increased firefighter safety, this might be a reasonable tradeoff, but I have not seen evidence that this is the case.

Fire Streams

Jason’s use of Lloyd Layman’s work as an illustration of how water fog is used in firefighting is misleading. Indirect attack is only one way in which a combination nozzle can be used in structural firefighting. Jason is correct in that indirect attack involves production of a large volume of steam to cool and inert a fire compartment or compartments and that this method of fire attack should not be used in compartments occupied by firefighters (or savable victims).

Jason states “the fog stream has a much larger surface ratio and little if any of the broken stream makes contact with solid surfaces or fuel source. Remember, our goal is to apply water to the fuel source, not to just cool off the thermal layer.” While, a fog stream has a much larger surface area than a straight or solid stream, the remainder of this statement presents a number of problems.

First it is important to distinguish between a fog stream and a broken stream (which are quite different). A fog stream has much smaller droplets (which appears to be Jason’s point) while a broken stream (such as that produced by a Bresnan distributor) has much larger droplets.

Jason’s second point that little if any of the water makes contact with solid surfaces of the burning fuel is in direct conflict with his claim that the fog pattern produces a large volume of steam to fill the compartment (as in Layman’s indirect attack). Due to the substantial energy required to heat water to its boiling point (specific heat) and vaporize it into steam (latent heat of vaporization) and the relatively low specific heat of the hot gases; water vaporized in the upper layer actually reduces the total volume of hot gases and steam in the compartment. Water vaporized on hot surfaces does not take appreciable energy from the hot gases and the volume of steam produced is added to the total volume of the upper layer, resulting in the lowering of the bottom of the layer and making conditions less tenable. For a more detailed discussion of gas cooling see my prior post Gas Cooling, Part 2, Part 3, Part 4, and Part 5. If in fact the water is not reaching hot surfaces, it would not have the effect that Jason describes. If it does reach the surfaces, resulting in the effect described, a fog pattern actually does cool hot surfaces and burning fuel. The fact of the matter is somewhere between these two extremes. Effective use of a combination nozzle allows for cooling of gases when this is the goal and cooling of hot surfaces and burning fuel when position allows direct attack.

I agree with Jason’s third point, that the goal is to “apply water to the fuel source, not just to cool off the thermal layer” [emphasis added]. However, if faced with a shielded fire and direct attack is not possible from the point of entry, it is necessary to cool the hot upper layer to reduce potential for ignition of the hot smoke (fuel) and reduce the thermal insult to the firefighters below. This requires a stream that is effective at cooling the gases (rather than only or primarily surfaces). Once it is possible to apply water directly onto the burning fuel, this is critical as gas cooling is not an extinguishing technique, but simply a way to more safely gain access to the seat of the fire. For additional discussion of shielded fires and application of gas cooling see my previous post Shielded Fires and Part 2.

It is indisputable that a fog pattern can be used to create a negative pressure at an opening such as a window or door to aid in ventilation and that a solid stream held in a stationary position and projected through the same opening will create less of a negative pressure and have less impact on ventilation. However, it is incorrect to state that the fog stream will always have this effect and thus will have a negative impact if used for interior firefighting. Development of the increased air movement described requires that the stream be positioned in an opening to create a negative pressure, thus influencing air flow. Intermittent operation on the interior does not produce the same result.

Jason Sowders states “Let’s leave ventilation to the truck companies. Our main focus for the initial stretch should be extinguishment.” I have no argument that the main focus of the first line stretched should be confinement and extinguishment of the fire. However, engine companies have a significant impact on ventilation (and are an essential part of this essential tactic) in that all openings created in the building (including the door that the line was advanced through) are ventilation openings. For more on the entry point as ventilation, see my earlier post Influence of Ventilation in Residential Structures: Tactical Implications Part 2 and the last several posts on door control; Close the Door! Were You Born in a Barn? and Developing Door Control Doctrine.

Jason also states “We have been fooled for many years believing that a curtain of water between you and the fire is protection. What is occurring is that you are pushing heat, fire, smoke, and other products of combustion out in front of you.”

There are several interesting issues with these claims. First, if a fog pattern did not provide effective protection from radiant heat, fog streams would be ineffective protection when dealing with exterior flammable gas fires. However, this is not the issue here. As demonstrated in tests conducted by Underwriters Laboratories (UL) on Horizontal (Kerber, 2011) and Vertical Ventilation (Kerber, in press) as well as additional tests conducted by the National Institute of Standards and Technology (NIST) and the Fire Department of the City of New York (FDNY) (Healey, Madrzykowski, Kerber, & Ceriello, 2013), water does not push fire (for more information see the UL Report and On-Line Training Program Impact of Ventilation on Fire Behavior in Legacy and Contemporary Residential Construction. When a stream is operated continuously as in a combination attack where the stream (fog, straight, or solid) is rotated to cover the ceiling, walls, and floor and water is vaporized on contact with hot surfaces and burning fuel, steam is produced and the air flow developed by the stream aids in pushing these gases away from the nozzle and hopefully, towards an exhaust opening (half of the ventilation equation). Coordination of fire attack and ventilation is always important, but in this case ventilation in front of the hoseline is critical to safe and effective extinguishment. This is true regardless of the type of nozzle and stream used.

Jason cites the disruption of the hot upper layer in the fire environment as a problem presented by application of water fog into the hot gases. He further asserts that a straight or solid stream will provide a more rapid knockdown by reaching the seat of the fire without premature conversion to steam or being carried away by convection currents. As with many of the other arguments in Jason’s post, there is an element of truth here, but not the entire story.

As discussed above, application of water in a manner to produce steam on contact with hot surfaces will in fact disrupt thermal layering (regardless of the type of stream), this has given rise to empirical (observed) evidence that application of water fog into the hot upper layer has adverse consequences. However, if applied at a flow rate and/or duration that results in vaporization in the hot upper layer, conditions improve. Penetration is often cited as an advantage of straight or solid streams. This is true, provided that the stream can be directly applied to the burning fuel. Reach of the stream becomes particularly important when working in large compartments that are well involved. In many cases, firefighters must gain access to the fire compartment prior to being able to make a direct attack on burning fuel and thus may have need first cool the hot gas layer on approach and then make a direct attack. These two tasks may be efficiently accomplished using a combination nozzle to cool hot gases with pulsed application of water fog and a straight stream for direct attack.

Jason emphasizes that solid stream nozzles produce a superior stream in comparison to that produced by a combination nozzle set on a straight stream. The primary rationale stated in this argument is that the stream is denser and droplets produced when the solid stream is deflected off the ceiling or walls are larger and have sufficient mass to reach the burning fuel without being vaporized in the hot gases or carried away by convection. As with several other of Jason’s arguments, this has an element of truth. Larger droplets are effective for direct attack due to their mass and smaller surface area, increasing the amount of water reaching the burning fuel. The effects of convection on a straight stream from a combination nozzle are far less pronounced in a compartment than they are when attempting a defensive direct attack on a large fire with a significant convection column.

Most Fire Departments

Jason asserts that “Most fire departments throughout the country are aware of the harmful effects of fog application and are teaching their recruits to use straight stream water application for interior structural firefighting”. I am uncertain if most fire departments are teaching that only straight or solid streams should be used for interior firefighting operations. However, I would dispute that fog application is “harmful”. There are potentially harmful effects of inappropriate water application regardless of the type of stream. Firefighters must understand water as an extinguishing agent and develop mastery in the use of their primary weapon (to use the military metaphor), the nozzle. Firefighters today are more aware of the need to cool hot smoke (fuel) in the upper layer, it is essential to understand the capabilities and limitations of each type of fire stream

Constant Change

Jason concludes with the statement “We must be ready for battle with effective hoseline selection, nozzle selection, and flow rates…. It is our duty to be proactive when it comes to the constant changes our profession brings.”  I agree completely! However, our strategies, tactics, and doctrine must be evidence based, must have a sound theoretical foundation and be supported by both scientific research and practical experience. Unfortunately, our profession continues to struggles to integrate these elements and is saddled with conclusions based on experience without understanding. Theory and scientific research does not trump experience, neither does experience trump scientific knowledge. Both are essential!

The issues of flow rate and stream selection are not one sided, there is evidence for the effectiveness of both water fog and solid stream application for control of fires in today’s fire environment. It is easy to examine the evidence and choose the facts that support our preconceived ideas (regardless of your perspective). It is much more difficult to objectively evaluate the evidence and determine what conclusions are actually supported. We must continue to ask why and question our assumptions!

Ed Hartin, MS, EFO, MIFireE, CFO

References

Healey, G., Madrzykowski, D., Kerber, S., & Ceriello, J. (2013). Scientific research for the development of more effective tactics; Governors Island experiments July 2012 [PowerPoint]. Gaithersburg, MD: National Institute of Standards and Technology (NIST).

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

Kerber, S. (2012). Analysis of changing residential fire dynamics and its implications on firefighter operational timeframes. Retrieved June 26, 2013 from http://www.ul.com/global/documents/newscience/whitepapers/firesafety/FS_Analysis%20of%20Changing%20Residential%20Fire%20Dynamics%20and%20Its%20Implications_10-12.pdf

Sowders, J. (2013) Nozzle Selection: Are We Defeating the Enemy? Retrieved June 26, 2013 from http://www.fireengineering.com/articles/2013/06/nozzle-selection–are-defeating-the-enemy-.html?sponsored=firedynamics

Door Control Doctrine

As discussed in my last post, doctrine is a guide to action rather than a set of rigid rules. Clear and effective doctrine provides a common frame of reference, helps standardize operations, and improves readiness by establishing a common approach to tactics and tasks. Doctrine should link theory, history, experimentation, and practice to foster initiative and creative thinking.

One way to frame the discussion necessary to develop doctrine that is applicable to a range of circumstances, is to use a series of scenarios presenting different conditions and examine what is similar and what is different. Ideally, firefighters will work together to integrate this theoretical discussion with their experience to develop sound doctrine based on their own context (e.g., staffing, building and occupancy types).

Fireground Scenarios

Important! Not all of the tactics presented in the questions are appropriate and others may be appropriate in one context, but not necessarily in another. For example, a lightly staffed engine may not have the option of offensive operations until the arrival of additional resources (barring a known imminent life threat), where a company with greater staffing may have greater strategic and tactical flexibility. These questions focus on the impact of strategic (offensive or defensive) tactical options on fire dynamics.

Scenario 1: The first arriving company arrives to find a small volume of smoke showing from around windows and doors and from the eaves on Side Alpha with low velocity, no air inlet is obvious. Performing a 360^o reconnaissance, the officer observes similar smoke and air track indicators on other sides of the building and that all doors and windows are closed. Several windows on Side Alpha (Alpha Bravo Corner) are darkened with condensed pyrolysis products and the home appears to have smoke throughout (smoke logged).

How do you think the fire will develop between arrival and initiation of offensive fire attack (assuming that adequate resources are on-scene for offensive operations) assuming no change in ventilation prior to fire attack.

The fire is likely in a ventilation controlled, decay stage. If the ventilation profile does not change prior to entry (e.g., doors are kept closed, windows remain intact), the heat release rate (HRR) from the fire will continue to decline and temperatures within the building will drop (but may still be fairly high when entry is made).

How would opening the front door prior to having a charged line at the doorway on Side Alpha impact fire development?

Increased ventilation will result in a significant and potentially rapid increase in HRR. The proximity of the door to the fire compartment and temperature in the fire compartment at the time that ventilation is increased will have a direct impact on the speed with which the fire returns to the growth stage (but still remaining ventilation controlled). The closer the air inlet to the fire and the higher the temperature, the more rapidly the fire will return to the growth stage.

How would horizontal ventilation of the fire compartment (Alpha/Bravo Corner) impact fire development if performed as soon as the hoseline is deployed to the (still closed) doorway on Side Alpha?

As noted in the answer to question 2, increased ventilation will result in an increase in HRR. As windows in the fire compartment are in closer proximity to the fire, taking the windows potentially will result in a more rapid return to the growth (but still ventilation controlled) stage. It is also important to consider that a window cannot be unbroken; selecting this ventilation option does not provide an option for changing you mind if you do not like the result.

What would be the impact on fire behavior if the engine company advanced the first hoseline to the windows; took the glass and applied water to the burning fuel inside the fire compartment prior to making entry through the door? How might this change if offensive fire attack was delayed (e.g., insufficient staffing for offensive operations)?

This is an interesting question! Research by UL, NIST, and FDNY has shown the positive impact of exterior application of water into the fire compartment in reducing heat release rate. However, as noted in the answer to the preceding question, a window cannot be unbroken. If this is simply a contents fire in the compartment where the window is broken and water is applied, the result is likely to be favorable with a temporary reduction in HRR due water applied on burning fuel. However, if the fire extended to other areas of the building which shielded from direct attack at this point of application, effectiveness of exterior application from this single location is likely to be limited.

How would opening the front door and horizontal ventilation of the fire compartment (Alpha/Bravo Corner) impact fire development if performed as soon as the hoseline is deployed to the doorway on Side Alpha?

Advice on coordination of tactical ventilation and fire attack has typically stated, don’t vent until a charged hoseline is in place. This is good advice, but requires a bit of clarification.

“As soon as the hoseline is deployed to the doorway” may simply mean that a dry line has been stretched and firefighters are donning their self-contained breathing apparatus (SCBA) facepieces while waiting for water. The fire will begin transition back to the growth stage as soon as tactical ventilation is performed. Depending on the time required for the firefighters to mask up, the line to be charged, air bled off, pattern checked, and the charged line advanced to the fire compartment(s), the HRR may increase significantly and conditions are likely to be quite a bit worse than if the door and window had remained closed until the hoseline was in place to begin offensive fire attack from the interior.

If tactical ventilation is performed after the line is charged and firefighters are ready to immediately make entry and quickly advance to the fire compartment, it is likely that the effect of increased ventilation will be positive. There may be some increase in HRR, but it is likely to be minimal due to the short distance and simple stretch from the front door to the fire compartment(s). Once direct attack has begun to control the fire, the increased ventilation will improve conditions inside the building.

Assuming that sufficient resources are on-scene to permit an offensive attack, when should the entry point be opened? Assuming that the door is unlocked, how should the fire attack crew approach this task?

Tactical size-up is critical for the crew assigned to offensive fire attack. This includes assessment of B-SAHF (Building, Smoke, Air Track, Heat, and Flame) indicators, forcible entry requirements, and assessment of fire attack requirements (e.g., flow rate, length of line, and complexity of the stretch).

The door should remain closed until the crew on the hoseline is ready to make entry; hoseline charged, air bled off, nozzle function and pattern checked, SCBA facepeices on, on-air. Check to see if the door is unlocked, but control the door (closed) and check conditions inside (visible fire, level of the hot upper layer, presence of victims inside the doorway) by opening the door slightly. The firefighter on the nozzle should do this check while the tools firefighter opens and controls the door. If hot smoke or flames are evident, the nozzle firefighter should cool the upper layer with one or more pulses of water fog (depending on conditions). The door should be closed while the crew assesses the risk of entry (e.g., floor is intact and fire conditions will permit entry from this location). If OK for entry; the crew can open the door and advance the line inside, while cooling the upper layer as necessary.

See Nozzle Techniques & Hose Handling: Part 3 for additional information on door entry procedure.

Once the hoseline is deployed into the building through the door on Side Alpha for offensive fire attack, should the door remain fully open or closed to the greatest extent possible? Why?

Ideally, the door will be closed after the hoseline is advanced through the doorway to limit the air supplied to the fire. How this is accomplished will depend on staffing. The door may be controlled by the fire attack crew or it may be controlled by the standby crew (two-out).

As discussed in the prior post Influence of Ventilation in Residential Structures: Tactical Implications Part 2, when the door is open, the clock is ticking! In the ventilation controlled burning regime, increased ventilation results in an increasing HRR as the fire returns to the growth stage. The timeframe for increased HRR is dependent on the proximity of the inlet to the fire, configuration of the building, and temperature in the fire area (higher temperature results in faster increase in HRR). Closing the door (even partially) slows the increase in HRR. Once the attack line begins direct attack, the door can be opened as part of planned, systematic, and coordinated tactical ventilation.

Assuming that this is a contents fire and horizontal ventilation will be appropriate, when and where should it be performed (describe the flow path from inlet to exhaust)?

As with most questions, the answer here is “it depends”. There are a few missing bits of information that are important to horizontal tactical ventilation. Wind direction and the location of potential openings. To keep things simple, assume that there is no wind and that the only potential openings in the fire compartment are two windows on Side Alpha at the Alpha/Bravo Corner.

Once direct attack has commenced, horizontal tactical ventilation can be performed from Alpha (doorway) to Alpha (windows in the fire compartment). As the top of the door and tops of the windows are likely to be approximately at the same level, there a bi-directional flow path (smoke out at the top and air in at the bottom) is likely to develop. However, the bottom of the door is lower than the windows which will provide increased air movement from the door to the fire compartment.

In discussing this question (and the entire topic of door control for that matter), some firefighters will undoubtedly raise the question of positive pressure attack (PPA) or positive pressure ventilation (PPV). These tactics may provide an effective approach in this scenario, but developing comprehensive tactical ventilation doctrine requires examination of all of the options to control both smoke and air movement, so we are starting with a look at anti-ventilation and tactical ventilation using natural means.

Scenario 2: The first arriving company arrives to find smoke showing with moderate velocity and a bi-directional air track (smoke out the top and air in the bottom) from an open door on Side Alpha. A moderate volume of smoke is also pushing from around windows and from the eaves on Side Alpha. Several windows on Side Alpha (Alpha Bravo Corner) are darkened with condensed pyrolysis products and a glow is visible inside in the room behind these windows. Performing a 360^o reconnaissance, the officer observes similar smoke and air track indicators on other sides of the building and that all doors and windows with the exception of the door on Side Alpha are closed. Returning to Side Alpha, the officer observes that the velocity of smoke from the open door has increased and flames at the interface between the smoke and air as it exits the doorway. The home appears to have smoke throughout (smoke logged).

How do you think the fire will develop between arrival and initiation of offensive fire attack (assuming that adequate resources are on-scene for offensive operations) assuming no change in ventilation prior to fire attack.

The fire is in a ventilation controlled burning regime (indicators include the limited ventilation provided by the single opening at the front door and flames at the interface between the smoke and air at the door). The open door will likely provide sufficient ventilation for the fire to continue its growth and extension from the compartment of origin along the flowpath to the front door.

How would the officer closing the front door prior to having a charged line at the doorway on Side Alpha (e.g., when performing the 360) impact fire development?

Based on the reported observations during 360^o reconnaissance, the only significant ventilation opening is the front door. The bi-directional air track indicates that this opening is serving as both an inlet and outlet. Closing the door will reduce the air supply to the fire and will reduce the HRR and slow worsening conditions outside the fire compartment. Ideally this would be done prior to starting the 360^o reconnaissance.

Assuming that sufficient resources are on-scene to permit an offensive attack and the door was closed during the 360, when should the entry point be opened? How should this task be approached?

As in Scenario 1, the door should be opened only when the crew on the hoseline is ready to make entry; hoseline charged, air bled off, nozzle function and pattern checked, SCBA facepeices on, on-air. The same door entry procedure described in Scenario 1 should be used as if the door had been closed on arrival.

How would horizontal ventilation of the fire compartment (Alpha/Bravo Corner) impact fire development is performed as soon as the hoseline is deployed to the open doorway on Side Alpha?

The outcome of tactical ventilation of the fire compartment will depend on sequence and timing. If the door remained open during initial size-up and while the line was being stretched, he fire would have continued to grow (limited by ventilation provided by the doorway and interior configuration of the building). Additional ventilation in this case would result in a rapid increase in HRR. If the door had been closed during the 360, the increase in HRR on ventilation of the windows would likely be somewhat slower as the HRR and temperature in the fire compartment would have dropped once the door was closed. In either case, HRR will increase while the charged line is being stretched from the entry point to the fire compartment. This is not necessarily a problem if the stretch is quick and the flow rate of the hoseline is adequate. It is essential that the crews stretching the line and performing ventilation understand the influence of their actions on fire behavior and are not surprised at the result.

Once the hoseline is deployed into the building through the door on Side Alpha for offensive fire attack, should the door remain fully open or closed to the greatest extent possible? Why?

As noted in Scenario 1, closing the door to the greatest extent possible after the line is inside will slow fire development until the hoseline is in place to begin a direct attack.

Assuming that this is a contents fire and horizontal ventilation will be appropriate, when and where should it be performed (describe the flow path from inlet to exhaust)?

The same basic approach would be taken as in Scenario 1. Once direct attack has commenced, horizontal tactical ventilation can be performed from Alpha (doorway) to Alpha (windows in the fire compartment).

Scenario 3: The first arriving company arrives to find smoke showing with moderate velocity and a bi-directional air track (smoke out the top and air in the bottom) from an open door on Side Alpha. A moderate volume of smoke is also pushing from around windows and from the eaves on Side Alpha. Flames are visible from several windows on Side Alpha (Alpha Bravo Corner) with a bi-directional air track (flames from the upper ¾ of the window with air entering the lower ¼). Performing a 360^o reconnaissance, the officer observes similar smoke and air track indicators on other sides of the building and that all doors and windows with the exception of the two windows and door on Side Alpha are closed. Returning to Side Alpha, the officer observes that the velocity of smoke from the open door has increased and flames at the interface between the smoke and air as it exits the doorway. Flames from the windows on Side Alpha are similar to when first observed. The home appears to have smoke throughout (smoke logged).

How do you think the fire will develop between arrival and initiation of offensive fire attack (assuming that adequate resources are on-scene for offensive operations) assuming no change in ventilation prior to fire attack.

The fire is likely in a ventilation controlled burning regime (indicators include the limited ventilation provided by the openings at the front door and windows. Existing ventilation will likely be sufficient for the fire to continue its growth and extension from the compartment of origin along the flowpath to the front door. As there are multiple ventilation openings (more cross sectional area), HRR is greater and as a result fire development and spread will be much more rapid than in Scenario 2.

How would the officer closing the front door prior to having a charged line at the doorway on Side Alpha (e.g., when performing the 360) impact fire development?

As the windows in the fire compartment have failed and are serving as ventilation openings (in addition to the front door), the fire will likely remain in a ventilation controlled growth stage even if the door is closed. However, closing the door will still reduce the air supply to the fire and will slow fire growth. In addition, elimination of the flow path between the fire compartment and front door will reduce heat transfer along this flow path.

Assuming that sufficient resources are on-scene to permit an offensive attack and the door was closed during the 360, when should the entry point be opened? How should this task be approached?

As in Scenarios 1 and 2, the door should be opened only when the crew on the hoseline is ready to make entry; hoseline charged, air bled off, nozzle function and pattern checked, SCBA facepeices on, on-air. The same door entry procedure described in the prior scenarios should be used.

How would horizontal ventilation of the fire compartment (Alpha/Bravo Corner) impact fire development if performed as soon as the hoseline is deployed to the open doorway on Side Alpha?

As the windows in the fire compartment have already failed, some ventilation of the fire compartment has already occurred. In that the fire is ventilation controlled, any additional ventilation will significantly increase HRR. With a ventilation controlled growth stage fire and high temperature in the fire compartment, the HRR will increase rapidly.

Once the hoseline is deployed into the building through the door on Side Alpha for offensive fire attack, should the door remain fully open or closed to the greatest extent possible? Why?

As in the previous two scenarios, the door should be closed to as great an extent possible after the hoseline is advanced inside the building. This will limit air to the fire, slow fire development, an reduce the flow path between the fire and the front door.

Assuming that this is a contents fire and horizontal ventilation will be appropriate, when and where should it be performed (describe the flow path from inlet to exhaust)?

As the windows in the fire compartment have already failed, they will continue to provide ventilation. Once a direct attack has been initiated, the front door may be opened to increase air flow and the efficiency of the horizontal ventilation from Side Alpha to Side Alpha.

As noted in the previous post, these questions were all based on a similar fire (different development based on the ventilation profile at the time of the first company’s arrival) in the same, simple building, a one story, wood frame dwelling. It is important to examine other levels of involvement and ventilation profiles in this building as well as other types of buildings and fire conditions with similar questions. Also give some thought to the impact of door control when using vertical ventilation in coordination with fire attack.

Additional Examples

The following video of pre-arrival conditions and initial fireground operations provides an additional opportunity to consider the impact of ventilation and the importance of door control.

Video 1: In the first video, the door is closed when the fire department arrives, but the fire has self-vented through a window on Side Delta.

 

How might effective door control have influenced fire development and the safety of companies operating at this incident?

Video 2: In this video, the front door is open when the fire department arrives and it appears that the fire may have self-vented on Side Charlie.

How might effective door control have influenced fire development and the safety of companies operating at this incident?

Video 3: In the last video, the front door is partially open and existing ventilation includes a window on Side Alpha and one or more openings on Side Charlie.

 

How might effective door control have influenced fire development and the safety of companies operating at this incident?

My next post will come back to the final set of questions regarding door control doctrine posed in Close the Door! Where You Born in a Barn?