Posts Tagged ‘nozzle techniques’

A Quick Review

As discussed in the last post in this series, military battle drills are an immediate response to enemy contact that requires fire and maneuver in order to succeed. Battle drills are initiated with minimal commands from the unit leader. Soldiers or marines execute preplanned, sequential actions in response to enemy contact.

This post discusses application of the battle drill concept in training firefighters to react appropriately on contact with our enemy (the fire) which requires fire (application of water) and maneuver (movement to a safer location) in order to succeed.

Remember: The key elements of a battle drill are fire and maneuver! This requires the ability to operate and maintain control of the hoseline while moving backward.

Working Without a Hoseline

In the United States, it is common for some companies working on the fireground to operate inside burning buildings without a hoseline (particularly when performing search). While common, this practice places firefighters at considerable risk when faced with extreme fire behavior. Without a hoseline your only defense against rapid fire progress is recognition of developing conditions and immediate reaction to escape to a safer location (see video below); which is not always possible. In some cases, firefighters fail to recognize developing conditions or the speed with which conditions will change. In other cases, firefighters are unable to escape or take refuge outside the flow path of hot gases and flames quickly enough.

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If your department’s operational doctrine includes companies working on the interior without a hoseline (or without being directly supported by a hoseline), it is essential that firefighters are trained to 1) recognize early indicators of potential for extreme fire behavior and 2) maintain a high level of awareness regarding locations which may provide an area of refuge. When confronted by rapidly worsening conditions, action to escape must be immediate and without hesitation.

Extreme Fire Behavior Battle Drill

Regardless of their assignment (e.g., fire attack, primary search), firefighters with a hoseline have a solid means of maintaining orientation, a defined primary escape route, and the ability to actively control the fire environment through application of water. However, as always, safe and effective operation in the fire environment is dependent on a solid size-up, dynamic risk assessment, maintenance of a high level of situational awareness, and proactively controlling the fire environment. The best way to deal with extreme fire behavior is to avoid it or prevent it from occurring. For more information on reading the fire and key fire behavior indicators related to potential for extreme fire behavior, see:

• 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
• Reading the Fire: Putting it all Together
• 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

In situations where you were unable to recognize potential for extreme fire behavior or you have been unable to control the fire environment, immediate action is required!

This is my nozzle, there are many like it but this one is mine. My nozzle is my best friend. It is my life. I must master it as I master my life. Without me it is useless, without my nozzle I am useless.

I will use my nozzle effectively and efficiently to put water where it is needed. I will learn its weaknesses, its strengths, its parts, and its care. I will guard it against damage, keep it clean and ready. This I swear.

As stated in the first paragraph of this adaptation of the United States Marine Corps Riflemans’ Creed, Without my nozzle I am useless.

The extent of thermal insult experienced in an extreme fire behavior event is dependent on both radiant and convective heat flux. Total radiant heat flux is dependent on temperature (of gases and compartment linings) and flow of hot gases. The higher the temperature and faster the speed of gas flow, the higher the heat flux. These scientific concepts drive the key elements of the extreme fire behavior battle drill. Extinguish or block the flames, cool hot gases, and maneuver out of the flow path to a point of egress or area of safer refuge.

Drill 8-Extreme Fire Behavior Battle Drill: Key hose handling and nozzle techniques when faced with extreme fire behavior are the ability to apply long pulses of water fog or maintaining a continuous flow rate while maneuvering backwards. This requires a coordinated effort on the part of the nozzle operator, backup firefighter, and potentially other firefighters working on the hoseline or at the point of entry.

Hose Handling & Nozzle Technique Drill 8 Instructional Plan

While this drill focuses on single company operations, it is important to extend this training to include crews operating backup lines. The importance, function, and operation of the backup line will be the focus of the next post in this series.

Not all That is Learned is Taught

When training to operate in a hazardous environment, avoid the mindset that it’s only a drill. As often observed, you will play the way that you practice. Extreme stress can activate inappropriate routine responses. For example, a Swedish army officer suddenly stood up while his unit was under fire while engaged in peacekeeping efforts in Bosnia. When asked about this response, he explained that in training, he often stood up while leading exercises (Wallenius, Johansson, & Larsson, 2002).

“A simple set of skills , combined with an emphasis on actions requiring complex and gross motor muscle operations (as opposed to fine motor control), all extensively rehearsed, allows for extraordinary performance levels under stress” (Grossman, 2008, p. 38).

When developing skill in nozzle technique and hose handline, and in particular the critical skills required to effectively perform this extreme fire behavior battle drill, it is essential to maintain critical elements of context such as appropriate use of personal protective equipment, position, and technique.

Ed Hartin, MS, EFO, MIFireE, CFO

References

Grossman, D. (2008). On-combat: The psychology and physiology of deadly conflict in war and peace. Millstadt, IL: Warrior Science Publications.

Wallenius, C. Johansson, C. & Larsson, G. (2002). Reactions and performance of Swedish peacekeepers in life-threatening situations. International Peacekeeping, 9(1), 133-152.

The first two posts in this series, Effective and Efficient Fire Streams, and Effective and Efficient Fire Streams: Part 2, discussed theoretical cooling capacity, fire stream efficiency, flow rate, nozzle design characteristics and methods of use. This post drills down with a look at the relationships between the pump, hose, and nozzle in developing effective and efficient fire streams.

Where to Start?

It is likely that the most common system for developing effective and efficient fire streams involves use of combination nozzles having a designed operating pressure of approximately 100 psi (690 kPa) and what my British and Australian colleagues would refer to as “layflat” hose with a diameter between 1-1/2” (38 mm) and 2” (52 mm). As this type of system seems to be common to most fire services (with a few variations), this is a good place to start.

Hydraulics

Developing effective and efficient fire streams requires an understanding of basic principles of fireground hydraulics. As discussed in earlier posts, each nozzle has a designed operating pressure. In order to provide this pressure at the nozzle, it is necessary to overcome loss of pressure in hoselines due to friction loss and increases in elevation.. Add To keep this discussion simple, the pump and nozzle will be at the same elevation.

Figure 1. Basic Handline Hydraulics

The major factors influencing friction loss in a hoseline are flow rate and diameter of the hoseline. The Pumping Apparatus Driver/Operator Handbook (IFSTA, 2006) identifies four friction loss principles:

First Principle: All other conditions being equal, friction loss varies directly with the length of the hoseline.

Second Principle: When hoseline diameter remains constant, friction loss varies approximately with the square of the increase in flow rate. Doubling the flow increases friction loss by a factor four.

Third Principle: At the same flow rate, friction loss varies inversely as the fifth power of the diameter of the hoseline (increasing hose diameter, even a small amount has a dramatic effect on friction loss. Increasing hose diameter from 1-1/2” (38 mm) to 1-3/4” (45 mm) reduces friction loss by 46% (1.50⁵/1.75⁵=0.46).

Fourth Principle: If hose diameter and flow rate are held constant, friction loss is independent of pressure.

Apparatus operators must understand these basic concepts and be proficient at determining the line pressure required to develop adequate nozzle pressure to produce the necessary reach and droplet size for effective and efficient fire control operations.

Scalability

Critical and optimal flow rate are dependent on the heat release rate from the fire. The higher the heat release rate, the higher the flow rate necessary to achieve fire control. However, the flow rate required for gas cooling (unignited gas phase fuel) is not so dependent on HRR! Cooling unignited gases is most effective at a considerably lower flow rate. 30 gal/min (115 l/min) to 60 gal/min (230 l/min) is often sufficient for gas cooling (unless compartment size is extremely large).

Single flow nozzles are simple to operate as control is limited to the angle of the fog pattern and the shutoff valve. The term single flow is a bit misleading in that flow can be varied using the shutoff valve. Partially opening the shutoff valve will provide a reduced flow rate. However, partially opening the valve also provides considerably lower nozzle pressure (at the orifice), resulting in poor stream performance (limited reach and large droplet size). If a nozzle is designed to develop the low flow rate and small droplet size that is typically optimal for gas cooling, it may not have sufficient flow for direct attack on larger fires or fires in larger compartments. On the other hand, nozzle designed for higher flow rates may be ideal for direct attack on larger fires or large compartments, but are inefficient and in some cases ineffective when used for gas cooling.

Ideally, the hose and nozzle system should be scalable to provide effective and efficient operation over a fairly wide range of flow rates. At the low end, the nozzle should be capable of gas cooling at 30 gpm (115 lpm). The upper end of flow capability for direct attack has room for considerable debate.

Some agencies such as the New South Wales Fire Brigades in Australia uses the Akron Turbojet with flow settings of 30, 60, 95, & 125 gal/min (115, 230, 360, 475 l/min). On the other hand, many fire departments in the United States use nozzles having upper end flow rates of 150-200 gal/min (568-757 l/min). Having a higher flow capability provides the ability to deal with higher HRR and larger size compartments typical in contemporary residential structures and commercial buildings.

Variable flow and automatic nozzles provide the capability to vary flow rate as needed to deal with varied tactical applications and fire conditions. However, each accomplishes this task in a different manner.

Variable Flow Nozzles

When using a variable flow nozzle, the size of the nozzle orifice can be changed manually to provide several specific flow rates at the designed nozzle pressure. This requires that the apparatus operator know the flow setting of the nozzle as well as the length of line in order to determine the line pressure required to develop the correct nozzle pressure. At first glance, it appears that changing flow rates on the fly would require a great deal of radio communication between the nozzle team and apparatus operator (communication of flow setting each time it is changed). However, this challenge can easily be overcome!

Consider what happens when the nozzle operator changes flow setting and the apparatus operator maintains the same line pressure. If the flow setting is reduced (decreasing the orifice size), flow rate will be decreased, reducing friction loss in the hoseline. As the line pressure remains the same, the pressure that is not used to overcome friction loss increases nozzle pressure. For example, if a 200’ (60 m) long 1-3/4” (45 mm) hoseline equipped with a variable flow nozzle such as an Akron Turbojet is flowing 125 gal/min (475 l/min) at a nozzle pressure of 100 psi (690 kPa) and the nozzle operator changes the flow setting to 30 gal/min (115 l/min) and discharge pressure remains constant, the flow rate will be reduced to 40 gal/min (150 l/min) at a nozzle pressure of 140 psi (965 kPa) (see Figure 2).

Figure 2. Changes in Flow Rate and Nozzle Pressure

Note: The preceding example is based on tests conducted with an Akron Turbojet variable flow nozzle.

How does the reduced flow rate and increased nozzle pressure impact on fire stream effectiveness and efficiency? Increased velocity of discharge (resulting from the higher nozzle pressure) results in reduced droplet size, increasing the effectiveness and efficiency of the stream when used for gas cooling. The reduced flow rate may be insufficient for direct attack on larger fires, but the nozzle operator can quickly return to a higher flow rate by adjusting the nozzle flow control. Pumping to deliver maximum flow allows the nozzle operator to select the flow rate and nozzle pressure that is appropriate based on conditions.

Automatic Nozzles

Automatic nozzles maintain a relatively constant nozzle pressure through a given flow range. The nozzle operator controls flow using the shutoff (opening the nozzle partially provides a lower flow rate than when the nozzle is opened fully).

The shutoff valve controls both water application and flow rate, automatic nozzles are a bit simpler to use, but unlike the example provided on how to maximize the capability with the variable flow nozzle, nozzle pressure remains constant (e.g., 100 psi (690 kPa).

System Design

The starting point for designing an effective system to develop effective and efficient fire streams needs to consider the desired flow rate, typical length of hoselines required, and tactical applications. Remember there is no universal, one size fits all, answer to this question. Fire services around the world successfully use a variety of different systems. Consider the following as a starting point:

• Both variable flow and automatic nozzles can be used effectively to apply water at varied flow rates. Automatic nozzles are simpler to operate (as they have fewer controls), but at lower flow rates are likely to develop larger droplets than variable flow nozzles operated at over 100 psi (690 kPa).
• Hoseline diameter should be sufficient to develop the desired flow rate given the likely attack line length. Remember that as hoseline diameter increases, friction loss decreases (but so may mobility).
• Pumping for maximum flow from the nozzle provides the nozzle operator with maximum flexibility as flow rate can be selected based on conditions. If other than maximum flow is selected as the standard flow rate it is important to train nozzle operators to request that the apparatus operator increase discharge pressure to provide maximum flow if needed.

The next post in this series will examine applications of high pressure and ultra-high pressure systems for developing effective and efficient fire streams. While considerably different than the system described in this post, this technology shows promise in expanding the range of tools available for fire control operations.

Ed Hartin, MS, EFO, MIFireE, CFO

References

International Fire Service Training Association (IFSTA). (2006). Pumping apparatus driver/operator handbook (2^nd ed). Stillwater, OK: Fire Protection Publications.

The previous posts in this series, examined the importance of proficiency in use of the firefighters’ primary weapon in offensive firefighting operations, and outlined several drills that can be used to develop proficiency in basic nozzle operation and hose handling.

• My Nozzle
• Basic Nozzle Techniques & Hose Handling
• Nozzle Techniques & Hose Handling: Part 2
• Nozzle Techniques & Hose Handling: Part 3

This post extends this examination of how to develop proficiency in nozzle operation and hose handling, presenting method or developing skill in working under conditions with poor visibility and application of indirect attack as an offensive firefighting tactic.

This is my nozzle, there are many like it but this one is mine. My nozzle is my best friend. It is my life. I must master it as I master my life. Without me it is useless, without my nozzle I am useless.

I will use my nozzle effectively and efficiently to put water where it is needed. I will learn its weaknesses, its strengths, its parts, and its care. I will guard it against damage, keep it clean and ready. This I swear [adapted from the Rifleman’s Creed, United States Marine Corps].

Operating Without Visual Reference

Drills to this point have been under conditions of good visibility where firefighters can observe nozzle pattern and fire stream effects. However, on the fireground it is critical that these skills can be used effectively under conditions of low or no visibility.

Sometimes it is necessary to go backward in order to move forward. One way to begin the process of developing the ability to work effectively with limited visibility is to go back to Nozzle Technique and Hose Handling Drills 1 & 2 and repeat these exercises with the firefighter’s breathing apparatus facepieces covered (unlike working in the dark, this makes it much easier for the instructors to observe and provide feedback). While this seems like an extremely slow and incremental process, it is likely to build a higher level of skill and require less time to develop proficiency than simply fumbling about in the dark!

Door Entry and Gas Cooling

In Nozzle Technique and Hose Handling: Part 3, door entry was illustrated at an exterior door. However, this method should be used anytime that firefighters encounter a closed door that may have hot gases or fire behind it. This becomes even more important when operating in a smoke (fuel) filled environment.

Smoke is fuel! The upper (hot gas) layer may contain a substantial mass of fuel that is ready to ignite. Flames exiting from a compartment door can ignite this fuel, resulting in rapid fire progression through the upper layer and into adjacent compartments. This phenomenon is demonstrated by CFBT-US Senior Instructor Trainer Matt Leech (LT Tualatin Valley Fire & Rescue) in Figures 1 through 3. While this demonstration involves use of a single compartment doll’s house and “porch roof”, the same phenomena can occur on a larger scale in any type of structure.

Figure 1. Accumulation of Fuel Overhead

Figure 2. Extension of Flames and Ignition of Fuel Overhead

Figure 3. Transition to Flaming Combustion Overhead

This simple demonstration illustrates the hazards presented by smoke overhead, the importance of gas cooling, and good door entry technique. While often overlooked, recognition of this hazard is not new. “Smoke contains unburned fuel and when mixed with air in the proper proportion becomes a flammable mixture” (Layman, 1955).

When working under conditions of limited visibility, other sensory feedback becomes even more important to the nozzle operator. It is essential that firefighters become familiar with audible indicators of stream performance. Think about the sound of a straight stream hitting the ceiling or a wall versus the sound of a fog pattern applied into the hot gas layer (without significant contact with compartment linings). Would you be attuned to the difference in sound? This is important when you can’t see the pattern being discharged. Changes in temperature can also be an important indicator. However, it is important to remember that perceived temperature is also influenced by moisture. Excess steam production (from water hitting hot compartment linings) may make it seem like the temperature is rising, when this is due to increased moisture content in the smoke and air. If it seems like it is getting hotter, it is important to recognize if this is due to worsening fire conditions, or inappropriate water application.

Drill 6-Operating Without Visual Reference: This drill integrates door entry, hose handling, and nozzle techniques (pulsing and painting) under conditions with limited visibility. The drill can be conducted with the facepiece covered, in darkness, or using cold smoke (e.g., from a smoke machine). Learners should begin by using good door entry technique on an exterior door and then move through several compartments (preferably of different sizes), encountering several doors (some of which should be closed) along the way to the seat of the “fire”. Alternately, this drill can be used to practice hose handling and nozzle technique in the context of primary search with a hoseline (or in support of crews performing search).

Hose Handling & Nozzle Technique Drill 6 Instructional Plan

Indirect Attack

Indirect attack is a commonly misunderstood firefighting tactic. Common misconceptions include:

• Indirect attack is only performed from the exterior of the building.
• Indirect attack will push fire throughout the building.
• Indirect attack involves banking water off the ceiling to reach burning fuel that is inaccessible to direct application of water (see Figure 4).
• Indirect attack and gas cooling is the same thing.

These statements are absolutely incorrect!

Figure 4. What Indirect Attack is NOT.

Several years ago I had a company officer that I worked with tell me that he had learned about a “new” fire control technique called the indirect attack at strategies and tactics class. I loaned him a small blue book titled Attacking and Extinguishing Interior Fires (Layman, 1955) and observed that this was not exactly a “new” idea.

The concept of the indirect attack was an outgrowth of extensive study of fuel oil fires within confined spaces conducted by the instructor staff of the US Coast Guard Firefighting School at Fort McHenry in Baltimore, Maryland during World War II (Layman, 1955). The term indirect, referred to application of water into a hot compartment, but not directly onto the burning fuel. Conversion of water to steam absorbed a tremendous amount of energy and the expansion of steam filled the compartment (and potentially adjacent compartments which may also have been involved in fire).

In 1947, Lloyd Layman completed his service with the US Coast Guard and returned to duty as Fire Chief with the Parkersburg West Virginia Fire Department. Over the next two years, Layman and the members of his department worked to implement the concept of indirect attack for structural firefighting. In 1950 Chief Layman delivered a presentation titled Little Drops of Water (Layman, 1950) which outlined the adaptation of indirect attack for structural firefighting. In 1952 he completed Attacking and Extinguishing Interior Fires (Layman, 1955), a textbook that provided a more comprehensive look at indirect attack including several case studies based on incidents in Parkersburg where this approach had been used successfully in dealing with both residential and commercial fires.

As presented by Layman, the indirect attack was generally performed from the exterior of the building. However, it is important to recognize historical context. In the late 1940’s respiratory protection (when it was used) was often limited to All Service Masks, which used a filter mechanism to remove toxic products of combustion (to some extent), but could not be used in significantly oxygen deficient atmospheres.

Layman’s Error: Chief Layman made a number of extremely important and astute observations, particularly with regards to the tremendous cooling capacity of water when it is not only heated to its boiling point, but also converted to steam. However, one of the major assumptions related to indirect attack was in error. Layman states: “The injection of water into a highly heated atmosphere results in rapid generation of steam…[increasing] the atmospheric pressure within the space (p. 36-37). This points to the Chief’s assumption that steam produced as water was evaporated in the hot gas layer added to the total volume of gas and vapor within the space (i.e., the volume of steam was added to the volume of smoke and hot gases in the compartment). As discussed in Estimating Required Fire Flow: The Iowa Formula [LINK]; this is incorrect, water vaporized as it passes through the hot gas layer actually reduces total volume (due to cooling of the hot gases). On the other hand, water that is vaporized in contact with hot surfaces (that did not significantly cool the gases as it passed through the hot gas layer) adds to total volume as expanding steam is added to the volume of hot gases within the compartment. The difference between indirect attack and gas cooling will be explored in detail in my next post on Fire Stream Effectiveness and Efficiency.

Figure 5. Indirect Attack

Drill 7-Indirect Attack from the Door: When faced with a fully developed fire in an enclosed area or a severely ventilation controlled fire (decay phase) that presents potential for a ventilation induced flashover or backdraft. Indirect attack may be an effective option for fire control. However, this tactic is not limited to exterior operations. Indirect attack can be initiated as part of the door entry procedure (exterior or interior doorway). If dynamic risk assessment indicates that entry is not viable due to fire conditions, the nozzle operator can use long pulses from the doorway (while the other member of the hose team controls the door) to apply water to hot surfaces, producing steam to gain control of conditions within the compartment prior to entry. This fire control method should be integrated with effective tactical ventilation (think planned, systematic, and coordinated).

Hose Handling & Nozzle Technique Drill 7 Instructional Plan

This approach can be extremely useful when the door to the fire compartment can be controlled and the hose team is presented with multiple priorities (persons reported and the need to control the fire to maintain the safety of interior operations). Figure 6 illustrates an example of how an indirect attack may be used when operating from the interior. In this scenario, the first arriving engine observes a fully developed fire in the bedroom on the A/D corner of a single family dwelling and receives information that an occupant is in the bedroom on the C/D corner. Rapidly developing fire conditions require immediate fire control. The crew makes entry from Side A, cools the hot gases overhead as they proceed to the fire compartment. As it is necessary to control the fire before proceeding past the involved compartment, they control the door, implement an indirect attack, and then extend an oriented search to locate the occupant while the nozzle operator protects the means of egress and maintains orientation for the firefighter performing the search in the adjacent compartments.

Figure 6. Application of Interior Indirect Attack.

While there are other tactical approaches that could be taken in this situation, use of an indirect attack allows the hose team to address both life safety (firefighters and occupants) and fire control tactical priorities.

Ed Hartin, MS, EFO, MIFIreE, CFO

References

Layman, L. (1955). Attacking and extinguishing interior fires. Boston, MA: National Fire Protection Association.

Layman, L. (1950). Little drops of water. Unpublished paper, presented at the Fire Department Instructors Conference (FDIC), Memphis, TN.

It is often stated and commonly believed that it takes gpm to overcome Btu. While I suspect that firefighters understand the underlying intent of this statement, it is actually incorrect as it is comparing apples and oranges. Flow rate is expressed in terms of volume and time (gal/m or l/m). However, Btu (or Joules) is a measure of quantity (more like volume than flow rate).

You can say that it takes gallons (or liters) to overcome Btu (or Joules), But the rate at which energy is absorbed by a fire stream must overcome heat release rate (energy released/unit of time). This concept points to the need for a higher flow rate when the heat release rate from a fire is larger. This leads to another common fire service saying: “Big Fire, Big Water”. While this is not completely incorrect, it is a bit misleading as it does not account for the efficiency of the fire stream in absorbing energy. Not all of the water that leaves the nozzle absorbs the same amount of energy.

Theoretical Cooling Capacity

Water is an excellent extinguishing agent because it has a high specific heat (energy required to raise its temperature) and high latent heat of vaporization (energy required to change it from water to steam). As illustrated in Figure 1, conversion of water to steam is most significant as it absorbs 7.5 times more energy than heating water from 20^o C (68^o F) to its boiling point.

Figure 1. Theoretical Cooling Capacity

However, this only tells us the theoretical cooling capacity of a single kilogram of water at 20^o C (68^o F) if it is raised to 100^o C (212^o F) and completely vaporized. Examining theoretical cooling capacity in terms of flow rate requires a bit more work.

Flow is defined in terms of gallons per minute (gal/m) or liters per minute (l/m) and theoretical cooling capacity of water was defined in terms of energy absorbed per second per unit mass (MJ/kg) we need to work through conversion to common units of measure.

While SI units are simpler to work with, I have worked cooling capacity out in both liters per minute (LPM) and gallons per minute (GPM). However, in that specific heat and latent heat of vaporization are applied to mass rather than volume and Watts are joules per second, it is first necessary to covert flow rate into kg/s

Figure 2. Flow Rate and Theoretical Cooling Capacity

This example assumes instantaneous heat transfer and 100% efficiency in conversion of water to the gas phase. Neither of which is possible in the real world!

Factors influencing effectiveness and efficiency of heat transfer (Svennson, 2002) include:

• Diameter (in the gas layer and on surfaces)
• Temperature (in the gas layer and on surfaces)
• Velocity (in the gas layer)
• Film formation (on surfaces)
• Temperature of the gas layer
• Surface temperature

Fire Stream Efficiency

The firefighter’s power is not simply related to flow rate, but flow rate effectively applied to transfer heat from hot gases and surfaces by changing its phase from liquid (water) to gas (steam). Extinguishing a compartment fire generally involves converting a sufficient flow (gal/m or l/m) of water to steam. So while the “steam” itself does not generally extinguish the fire, the energy absorbed in turning the water to steam has the greatest impact on fire extinguishment.

Experimental data (Hadjisophocleous & Richardson, 2005; Särdqvist, S., 1996) has shown that the cooling efficiency of water in both laboratory experiments and actual firefighting operations ranges from 0.2 to 0.6. Särdqvist (1996) suggests that an efficiency factor of 0.2 be used for interior fog nozzles. Based on my personal observations (but no experimental data), I think that Särdqvist’s efficiency factor of 0.2 might be just a bit on the low side. Barnett (as cited in Grimwood,2005) suggests that an efficiency factor of 0.5 be used for solid or straight stream application and 0.75 for fog application. The following table takes a slightly more conservative approach, using 0.6 as an average efficiency factor.

Figure 3. Flow Rate and Adjusted Cooling Capacity

Figure 3 is provided to illustrate the impact of efficiency (or lack thereof) on fire stream cooling capability. The key point is that actual cooling capability is considerably less than the theoretical cooling capacity. Another complication is that in addition to nozzle performance characteristics, nozzle efficiency is also dependent on the skill of the nozzle operator, the manner in which water is applied (straight stream, narrow fog pattern, wide fog pattern), the configuration of the space, and fire conditions. Unfortunately, there is no standardized test with specified conditions that permits comparison of different nozzles and/or methods.

However, the concept of efficiency gives rise to an interesting question. Does a nozzle flowing 100 gpm with an efficiency factor of 0.6 have the same extinguishing capability as 200 gpm nozzle with an efficiency factor of 0.3. This is simple math! The cooling capacity would be identical. While the practical application is more complex (as we do not really know the efficiency factors for the two nozzles and manner in which they are being used), this is worth thinking about.

Flow Rate or Heat Absorption Capacity

CFBT-US Senior Instructor Trainer Matt Leech (LT Tualatin Valley Fire & Rescue) proposed (half in jest) that nozzles should be labeled with their potential cooling capacity rather than flow rate. While this idea did not get significant traction, it is important for firefighters to recognize that flow rate and fire stream characteristics have a significant impact on potential cooling capacity.

Fire Stream Effectiveness

Safe, effective and efficient fire control requires:

• Water application to control the fire environment as well as direct attack on the fire
• Appropriate flow rate for the tactical application (cooling hot, but unignited gases may be accomplished at a lower flow rate than direct attack on the fire)
• Direct attack to exceed the critical flow rate based on the fire’s heat release rate
• Sufficient reserve (flow rate) be available to control potential increases in heat release rate that may result from changes in ventilation
• Water application in a form appropriate to cool its intended target (i.e., small droplets to cool hot gases or to cover hot surfaces with a thin film of water)
• Water to reach its intended target (fog stream to place water into the hot gas layer and a straight or solid stream to pass through hot gases and flames and reach hot surfaces)
• Control of the fire without excessive use of water

Accomplishing this requires different stream characteristics at different times. The characteristics that are optimal for gas cooling are likely quite different than for cooling hot surfaces, particularly when dealing with fully developed fire conditions in a large compartment.

Priorities

As regular readers have likely noted my posting schedule has been a bit off of late. My responsibilities as the new Fire Chief with Central Whidbey Island Fire & Rescue preclude the necessary research and writing necessary to constantly post twice weekly. I will be scaling back to a single post on Thursday for the next few months while I get a handle on my new job and get my family moved to Whidbey Island.

Ed Hartin, MS, EFO, MIFIreE, CFO

References

Grimwood, P. (2005) Firefighting Flow Rate: Barnett (NZ) – Grimwood (UK) Formulae. Retrieved January 26, 2008 from http://www.fire-flows.com/FLOW-RATE%20202004.pdf

Hadjisophocleous, G.V. & Richardson, J.K. (2005). Water flow demands for firefighting. Fire Technology 41, p. 173-191.

Särdqvist, S. (1996) An Engineering Approach To Fire-Fighting Tactics Sweden, Lund University, Department of Fire Safety Engineering

Svennson, S. (2002). The operational problem of fire control (Report LUTVDG/TVBB-1025-SE). Sweden, Lund University, Department of Fire Safety Engineering.

The previous posts in this series, examined the importance of proficiency in use of the firefighters’ primary weapon in offensive firefighting operations, and outlined several drills that can be used to develop proficiency in basic nozzle operation and hose handling.

• My Nozzle
• Basic Nozzle Techniques & Hose Handling
• Nozzle Techniques & Hose Handling: Part 2

Developing proficiency in nozzle use is somewhat like building skill with a rifle. Understanding what end of the rifle the bullet comes out of and that the rifle is fired by pulling the trigger is the easy part, learning to consistently hit what you are aiming at over varied distances requires considerably more effort.

This is my nozzle, there are many like it but this one is mine. My nozzle is my best friend. It is my life. I must master it as I master my life. Without me it is useless, without my nozzle I am useless.

I will use my nozzle effectively and efficiently to put water where it is needed. I will learn its weaknesses, its strengths, its parts, and its care. I will guard it against damage, keep it clean and ready. This I swear [adapted from the Rifleman’s Creed, United States Marine Corps].

In the first three nozzle drills learners develop basic proficiency in basic nozzle use (fixed position), integrating nozzle use while moving a hoseline forward and back, and use of the nozzle while moving the hoseline through varied size compartments. This post will provide an overview of door entry procedures.

Door Entry Concepts

For many firefighters, door entry is simply a process of remembering to “try before you pry” and then figuring out how to force the door if it is locked. For others it is simply kicking the door in! Often overlooked is the fact that the entry point is a ventilation opening; sometimes an inlet, sometimes an outlet, and often both. When the fire is ventilation controlled, opening the door and increasing air flow to the fire will result in increased heat release rate. Depending on the stage of fire development and conditions within the compartment or structure, this may result in extreme fire behavior such as a ventilation induced flashover or backdraft (see Fuel & Ventilation).

As illustrated in Figure 1, firefighters often encounter rapidly changing conditions after making entry. In this incident, flashover occurred less than 60 seconds after firefighters opened the door and made entry (see Situational Awareness is Critical for additional information on this incident)

Figure 1. Rapidly Changing Conditions

Note: Photos by Probationary Firefighter Tony George, Prince Georges County Fire Department.

Safe and effective firefighting operations depend on effectively reading the fire and recognizing potential stages of fire development and burning regime (see previous posts on Reading the Fire) and effective tactical operations to take control of the fire environment. Door entry is an important element in this process.

Door Entry Procedure

As you review this door entry procedure, you may find that it makes sense to you exactly as presented. On the other hand, you may find that some elements (e.g., size-up and dynamic risk assessment) make sense, but other components (e.g., cooling overhead prior to opening the door) require a bit more of a leap. The elements of the door entry process reinforce one another, adopt the elements that make sense to you, but consider the value of the procedure as an integrated process. The process outlined is not followed in a lock-step manner, it is important for the hose team to take action based on observed conditions.

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!

Control the Door: If the door is open, close it. If it is closed, don’t open it until you are ready. Heat release requires oxygen, controlling the air supply to the fire controls heat release rate. If you force the door in preparation for making entry, make sure you maintain control of it.

Gas Cool Above the Door and Assess, and Control Interior Conditions: When you open the door to assess conditions inside, hot smoke will likely exit at the top of the door. If it is hot enough it may auto-ignite. The hazard presented by the exiting smoke can be reduced by applying two short pulses above the door just as it is opened (the firefighter controlling the door should crack the door as the first pulse is applied).

The door should be opened sufficiently to allow the nozzle operator to visualize interior conditions, but not so much that a large amount of air is introduced (no magic number on how far to open, “it depends”). If hot smoke is present, the nozzle operator should cool the gases inside the compartment from the doorway. This may involve a short pulse or two or it may involve a longer pulse, depending on the size of the compartment and conditions (again, this requires the nozzle operator to think!).

Close the Door: While there is often a sense of urgency to make entry (due to developing fire conditions, persons reported, etc.), this step is important as it provides an opportunity for a focused risk assessment.

Risk Assessment: Is it safe to make entry (or to make entry through this opening)? Fully developed fire conditions inside the door or a pulsing air track (indicating potential for vent induced flashover or backdraft) may indicate a need to consider alternative tactics).

Entry: If it is safe to make entry, the process of cooling above the door as it is opened is repeated and hot gases inside the compartment are cooled as the hose team makes entry.

Figure 2. Door Entry Procedure

Note: Adapted from video clip 00000010 on the 3D Firefighting: Training, Techniques and Tactics Resource DVD.

Remember: The purpose of door entry procedures is to reduce risk of extreme fire behavior during and immediately after entry! Door entry procedures should be used any time that hot smoke or flames may be on the other side of the door. These procedures are used at exterior doors when making entry and on closed doors encountered inside the building.

Drill 4-Door Entry-Inward Opening Doors: Many doors (particularly interior and exterior residential) open inward (away from the nozzle team), door entry requires that the hose team integrate forcible entry, door control, and nozzle operation. Practicing door entry procedures with a variety of inward opening door configurations (location of the door in relation to walls and with varied size compartments) is critical in developing proficiency.

Drill 5-Door Entry-Outward Opening Doors: Commercial doors (and some interior doors) will open outward (towards the hose team). Outward opening doors require a somewhat different position when performing door entry. Firefighters must develop skill in performing door entry with both inward and outward opening doors.

Hose Handling & Nozzle Technique Drill 4 & 5 Instructional Plan

These two drills can be conducted using any door where water can be applied. However, a free-standing door entry prop (see Figure 3) provides a simple and effective aid to developing door entry proficiency.

Figure 3. Door Entry Prop

Note: Photo by Inspector John McDonough, ASFM, New South Wales Fire Brigades.

Alternately, a forcible entry prop could be used to integrate the forcible entry component of the door entry process.

Drills

As discussed in Nozzle Techniques and Hose Handling: Part 2 [LINK], it is essential for firefighters to have the ability to react immediately to deteriorating conditions. While battle drills will be discussed in depth in a subsequent post, consider how this concept might apply during door entry. What action should the hose team take if they encounter strong indicators of backdraft conditions at the doorway (e.g. pulsing air track, thick (optically dense) smoke)? How should the hose team react if, despite following good practice, conditions worsen immediately after entry?

Ed Hartin, MS, EFO, MIFireE, CFO

References

Grimwood, P., Hartin, E. McDonough, J. & Raffel, S. (2005). 3D firefighting: Training, techniques, and tactics. Stillwater, OK: Fire Protection Publications.

Understanding how to develop fire streams has been critical since firefighters began to use hose and nozzles (Figure 1) to increase the effectiveness and efficiency of firefighting operations.

Figure 1. In the Beginning!

When selecting handline nozzles, firefighters and fire officers generally consider four nozzle characteristics: 1) type of nozzle (combination or solid stream/smoothbore), 2) fixed or variable flow, 3) flow rate, and 4) designed operating pressure. Saving the big debate regarding combination and solid stream/smoothbore nozzles for another post, this post will focus primarily on nozzle pressure and flow rate.

Nozzle Function

A little over 20 years ago I was asked an interesting question by a newly hired recruit firefighter. She had no prior fire service experience and was puzzled by the hose evolutions being taught during her academy. As I attempted to help her make sense of these alien concepts, she finally asked “What’s the pump for? Why don’t we just put the nozzle on the end of the hose from the hydrant?” Her instructors may have assumed that hydraulics was a topic for apparatus operators or that everyone understood the basic concepts involved in developing an effective fire stream.

The primary function of a nozzle is to increase the velocity of water flowing from the hoseline. A fire stream must have sufficient velocity for water to reach from the nozzle to the intended target. The simple equation illustrated in Figure 2 is essential to understanding nozzle design and performance. Flow rate (the quantity of water) from a nozzle is dependent on the area of the opening and the velocity of the water being discharged (for a given size opening, the greater the velocity the higher the flow rate).

Figure 2. Important Equation

As indicated in the equation Q=AV, flow rate is related to velocity and the size (area) of the nozzle orifice. This relationship is simple to understand when looking at solid stream/smoothbore nozzles. Nozzle pressure translates to velocity at the tip. For a given size tip, increasing nozzle pressure increases velocity and thus the flow rate from the tip. For example, a 1-1/4” (32 mm) tip will flow 317 gpm (1200 lpm) at 50 psi (345 kPa). Increasing the nozzle pressure to 80 psi (552 kPa) increases the flow rate to 401 gpm (1518 lpm). Flow rate can be varied by changing the size of the tip, the nozzle pressure, or both.

Visualizing nozzle orifice size is a bit more difficult with combination nozzles. Most combination nozzles use a deflection stem (see Figure 3) to form the fog pattern. The nozzle orifice is an annular (ring shaped) space between the deflector and the body of the nozzle tip.

Figure 3. Combination Nozzle Orifice

The change in direction at the deflection plate results in formation of small droplets of water. Nozzles may also have fixed teeth or a spinning, toothed turbine to aid in the production of appropriate sized droplets as water leaves the nozzle.

Nozzle Pressure and Droplet Size

Water is an excellent extinguishing agent because it has a high specific heat (energy required to raise its temperature) and high latent heat of vaporization (energy required to change it from water to steam). Of these two factors, conversion of water to steam is most significant as it absorbs 7.5 times more energy than heating water from 20^o C (68^o) to its boiling point. The firefighters’ power is not simply related to flow rate, but flow rate effectively applied to transfer heat from hot gases and surfaces by changing its phase from liquid (water) to gas (steam). Extinguishing a compartment fire generally involves converting a sufficient flow (gpm or lpm) of water to steam. So while the “steam” itself does not generally extinguish the fire, the energy absorbed in turning the water to steam has the greatest impact on fire extinguishment

Where the water is vaporized into steam depends on the method of fire control being used (direct attack, indirect attack, or 3D gas cooling). In direct attack water is vaporized on burning and pyrolyzing fuel surfaces to slow and stop the process of pyrolysis. Water is also vaporized on contact with hot surfaces in an indirect attack, but in this case the purpose is to produce a sufficient volume of steam to fill the compartment, achieving fire control or mitigating potential for extreme fire behavior such as a backdraft. Gas cooling on the other hand requires that the majority of the water be vaporized in the hot gas layer. This cools the hot gases (fuel) overhead, providing buffer zone and safer work environment for firefighters. It is important to remember that gas cooling is not an extinguishing technique, but merely one tool in controlling the fire environment.

Heat moves from objects of higher temperature to objects of lower temperature until temperature equalizes. Key factors in the speed of heat transfer are the difference in temperature and surface area of the materials. In the fire environment, burning fuel, nearby surfaces, and hot gases are considerably higher temperature than the water used for fire control and extinguishment. Surface area of the water in contact with the material being cooled is extremely significant in determining the speed of heat transfer. A larger surface area in relation to the amount of water will result in faster heat transfer and more rapid cooling.

If the volume of water remains the same, reducing droplet size increases surface area substantially. For example if droplet size is reduced by half, surface area increases by a factor of four (see Figure 4).

Figure 4. Droplet Diameter and Surface Area

Note. Adapted from Water and Other Extinguishing Agents (p. 194) by Stefan Särdqvist, 2002, Karlstad, Sweden: Raddningsverket. Copyright 2002 by Stefan Särdqvist and the Swedish Rescue Services Agency

Increased surface area increases heat transfer as droplets travel through the hot gas layer, rapidly reducing temperature. However, the down side of smaller droplets is that they do not travel as far and may not be able to penetrate a large distance in an extremely hot environment, making a fog pattern with small droplets potentially less effective in direct attack or when working in an extremely large compartment. Fortunately, when a fog pattern is adjusted to a straight stream much (but not necessarily all) of this problem is overcome.

What does nozzle pressure have to do with droplet size? Nozzles do not produce uniform droplet sizes. The fog pattern developed by a typical combination nozzle produces a mix of small and larger droplets. However, average droplet size and the percentage of droplets that are 0.3 mm (0.012”) in diameter is dependent on both nozzle design and pressure. However, for any nozzle design, increased nozzle pressure will result in smaller droplets.

Gresham Fire & Emergency Services conducted a series of qualitative tests on droplet size produced by the Task Force Tips Dual-Pressure Mid-Force Nozzle operating at 50 psi (345 kPa) and 100 psi (689 kPa). Droplet size was assessed by examining hang time, the time which droplets remained suspended in the air after a short pulse of water fog (smaller droplets remain suspended for a longer time while large droplets fall to the ground more quickly). Results of this test were captured on video and synched to ensure that the visual comparison was at the same time after the nozzle was closed. As illustrated in Figure 5, with the same flow rate, the nozzle pressure of 50 psi (345 kPa) resulted in larger droplets than a nozzle pressure of 100 psi (689 kPa).

Figure 5.

Nozzles operating at a lower pressure will have larger droplet size. This does not impact substantially on direct attack, but can have a significant impact on the effectiveness and efficiency of these nozzles when used for gas cooling. This does not mean that they cannot be used! It simply means that they will be less effective and are likely to result in less efficient vaporization of water (more water will end up on the floor).

Impact on Operations

While it is important to understand the underlying principles related to nozzle design and performance, it is even more important to understand the impact of these concepts on firefighting operations. The next post in this series will examine the concepts of efficiency and effectiveness in greater depth and why effective cooling capacity may be more important than simply looking at flow rate.

Ed Hartin, MS, EFO, MIFireE, CFO

References

Särdqvist, S. (2002). Water and other extinguishing agents. Karlstad, Sweden: Raddningsverket (Swedish Rescue Services Agency).

Prior posts in this series, My Nozzle and Basic Nozzle Techniques & Hose Handling, examined the importance of proficiency in use of the firefighters’ primary weapon in offensive firefighting operations.

This is my nozzle, there are many like it but this one is mine. My nozzle is my best friend. It is my life. I must master it as I master my life. Without me it is useless, without my nozzle I am useless.

I will use my nozzle effectively and efficiently to put water where it is needed. I will learn its weaknesses, its strengths, its parts, and its care. I will guard it against damage, keep it clean and ready. This I swear [adapted from the Riflemans Creed, United States Marine Corps].

It is critical that firefighters have both a sound understanding of nozzle performance and skill in the use of their primary weapon. In Figure 1, Assistant Superintendent Mohamed Roslan Bin Zakaria, Bomba dan Penylamat, Malaysia examines stream characteristics from an Akron Turbojet. Note the change in droplet size as the nozzle is closed (droplet size increases as pressure drops). In a short pulse opening and closing the nozzle quickly minimizes production of large droplets that are unlikely to vaporize in the hot gas layer. In long pulses, closing the nozzle slowly increases the percentage of large droplets, but this is a necessary tradeoff to prevent excessive water hammer.

Figure 1. Determining Stream Characteristics

Note: Photo by Shan Raffel, ASFM, CMIFireE, EngTech.

This post continues with a discussion of training methods that can be used to develop proficiency in nozzle techniques and hose handling while deploying hoselines and in compartments having varied configurations. Continuing with our military metaphor, we will be practicing fire and maneuver.

Instructional Concepts

As discussed in Basic Nozzle Techniques and Hose Handling this sequence of drills is designed using the Simplifying Conditions Method (Reigeluth, 1999). This approach moves from simple to complex, beginning with the simplest version of the task that represents the whole and moves to progressively more complex versions until the desired level of complexity is reached. In the case of nozzle technique and hose handling, this involves moving from basic, individual skills, to team skills, and on to integration of physical skills and decision-making.

While modeling a specific technique (such as the short pulse) can be helpful in aiding the learners in developing basic skill, there is a danger. Technique is often mimicked without thought to why it is performed in a particular manner under specific circumstances. Demonstration of a short pulse with a 40o fog pattern (which might be appropriate in a small room) becomes “that is how all short pulses must be performed”. As the learners complete Hose and Nozzle Technique Drills 2 and 3, it is critical to provide changing conditions and encourage the learners to adapt their technique based on conditions.

Drill 2-Hose Handling and Nozzle Operation: Firefighters often lose focus on nozzle technique and operation when they are moving. This drill provides an opportunity for the firefighter with the nozzle and backup firefighter to develop a coordinated approach to movement and operation.

Hose Handling & Nozzle Technique Drill 2 Instructional Plan

Drill 3-Nozzle Operation Inside Compartments: Deployment of hoselines inside a building requires a somewhat different set of skills than simply moving forward and backward. Movement of hoselines around corners and adjustment of nozzle pattern to cool gases in hallways and varied size compartments are important additions to the firefighters’ skill set and provide the next step in developing proficiency in nozzle use.

Hose Handling & Nozzle Technique Drill 3 Instructional Plan

Battle Drills

Analysis of firefighter line-of-duty deaths (LODD) during structural firefighting operations points to the need for highly disciplined, immediate, and appropriate response to rapidly deteriorating conditions. In terms of military small unit tactics, battle drills provide a standardized, collective action rapidly executed without application of a deliberate decision making process (US Army, 1992).

Adapted to firefighting operations, Battle Drills:

• Require minimal leader orders to accomplish and are standard throughout the department
• Are sequential actions vital to success in firefighting operations or critical to preserving life
• Apply to individual companies or teams
• Are trained responses to changing conditions or leader’s orders
• Represent mental steps followed for actions followed in training and firefighting operations

As a starting point for discussing this concept, give some thought to what situations might require a pre-planned and trained set of actions during offensive firefighting operations. For example, this might apply to locating a victim while deploying a hoseline for fire attack, rapidly deteriorating conditions, breathing apparatus malfunction, etc. Also consider how hose handling and nozzle techniques might apply in each of these situations.

Ed Hartin, MS, EFO, MIFireE, CFO

References

Reigeluth, C. (1999). Elaboration theory: Guidance for scope and sequence decisions. In C.M. Reigeluth (Ed.) Instructional-design theories and models: A new paradigm of instructional theory volume II. Mawah, NH: Lawrence Erlbaum Associates.

United States (US) Army. (1992). FM 7-8 Infantry rifle platoon and squad. Washington, DC: Headquarters, Department of the Army

The previous post in this series, My Nozzle, examined the importance of nozzle knowledge and skill in using the firefighter’s primary weapon in offensive firefighting operations.

Figure 1. Practice is Essential to Effective Nozzle Technique

Note: These Fire Officers from Rijeka, Croatia are practicing the short pulse to place water fog into the hot gas layer. Droplet size, cone angle, position of the nozzle, and duration of application have placed water in the right form exactly where it was intended.

This is my nozzle, there are many like it but this one is mine. My nozzle is my best friend. It is my life. I must master it as I master my life. Without me it is useless, without my nozzle I am useless.

I will use my nozzle effectively and efficiently to put water where it is needed. I will learn its weaknesses, its strengths, its parts, and its care. I will guard it against damage, keep it clean and ready. This I swear [adapted from the Riflemans Creed, United States Marine Corps].

This post continues with a discussion of training methods and techniques that can be used to develop proficiency in nozzle techniques and hose handling.

Limitations in Fire Service Instructional Methods

Fire service instructor training and related instructional methods have direct linkage to the philosophy of vocational education that evolved in the United States in the early 1900s (Hartin, 2004). The philosophy of vocational education that evolved in the first half of the 20^th century put forth a mechanistic view of training and vocational education in which the goal is efficient production of trained individuals (Allen, 1919; Prosser & Allen, 1925). In early fire service instructor training, basic concepts of vocational education were combined with behaviorist psychological concepts of positive and negative reinforcement to guide learning. Over the last four decades, fire service instructor training has evolved to include humanist perspectives on motivation and the characteristics of adult learners. However, the basic principles used in training factory workers to perform simple repetitive tasks remain the meat and potatoes of this theoretical stew. All very interesting, but what does this have to do with nozzle technique?

The dominant focus of most fire service instructor training programs is on classroom instruction and to a lesser extent on demonstration of basic skills as an instructional method. Less focus is placed on effective methods for skills instruction (other than demonstration) and more importantly how to coach and provide effective feedback during skills instruction. Effectively and efficiently developing firefighters’ psychomotor skills requires a somewhat different focus.

There is a commonality between firefighters and athletes. Both require development of a wide range of physical and mental skills as well as underlying knowledge. A tremendous amount of research has been conducted on effective approaches to development of skill and proficiency in sport. Kinesiology (the science of human movement) and sport psychology provide a useful starting point for improving fire service skills training. While this post is focused on nozzle techniques and hose handling, the underlying theories can be applied to many other skills. It is essential that both the coach and the learner not only understand what needs to be done and how to do it, but why!

Motor Learning and Performance

A motor skill can be conceptualized as a physical task such as operating a nozzle or stretching a charged hoseline through a building. However, there are a number of dimensions on which these types of task can be classified:

• Task organization (simple, single task or multiple, interconnected tasks)
• Importance of motor and cognitive elements (doing or thinking)
• Environmental predictability (consistent or variable conditions)

Simply opening and closing the nozzle is a discrete task that predominantly involves motor skill, and takes place in a fairly predictable environment (the firefighters’ position may change, but the nozzle remains the same). However, when placed in the context of hoseline deployment inside a structure with variable fire conditions things change quite a bit. This involves serial (multiple, sequential) tasks and requires both physical and cognitive (decision-making) skills, in a somewhat predictable, but highly variable environment. This explanation makes things seem a bit more complicated than they appear at first glance!

Motor learning can be divided into several relatively distinct stages (Schmidt & Wrisberg, 2008). In the verbal-cognitive stage, learners are dealing with an unfamiliar task and spend time talking and thinking their way through what they are trying to do. As learners progress to the motor stage, they have a general idea of the movement required and shift focus to refining their skill. Progression through the motor stage often requires considerable time and practice. Some learners progress to the autonomous stage in which action is produced almost automatically with little or no attention. Other than the newest recruits, most firefighters are in the motor stage of learning when developing skill in nozzle techniques and hose handling.

Developing an understanding of motor performance and learning requires a conceptual model. However, in that many of you are likely to be less excited about learning theory than I am, I will make an effort to limit this to a simple framework.

1. Stimulus Identification: Recognize the need for physical action
2. Response Selection: Determination of the action needed.
3. Response Programming: Preparation and initiation of the required action.
4. Feedback: Determination of the effectiveness of the action (this loops back to stimulus identification and the process begins again).

In some cases, feedback is obtained during the action and corrective action can be taken during task performance (closed loop control). In other (shorter duration) tasks, feedback is received after the task is completed (open loop control)

Many nozzle techniques such as application of a short pulse of water fog into the hot gas layer involve open loop control as the action is completed before the firefighter can receive and process feedback on the effectiveness of the action. Training must develop sufficient skill (and preferably automaticity) to allow firefighters to apply various nozzle techniques with minimal conscious thought to allow focus on maintaining orientation in the building and key fire behavior indicators.

While there is much more to the story, this limited explanation of motor learning and performance provides a starting point to understand why the nozzle technique and hose handling drills are important and why they are designed the way that they are.

Nozzle Technique and Hose Handling Drills

One more bit of learning theory before we get our hands on the nozzle. This sequence of drills is designed using the Simplifying Conditions Method (Reigeluth, 1999). This approach moves from simple to complex, beginning with the simplest version of the task that represents the whole and moves to progressively more complex versions until the desired level of complexity is reached. In the case of nozzle technique and hose handling, this involves moving from basic, individual skills, to team skills, and on to integration of physical skills and decision-making.

Once basic proficiency is developed in simple tasks (such as the short pulse, long pulse, penciling, and painting), practice should be randomly sequenced (rather than blocked into practice of a single skill). In addition, practice should be distributed over a number of shorter sessions, rather than massed into fewer, but longer sessions. For more information on design of effective and efficient practice sessions, see Motor Learning and Performance (Schmidt & Wrisberg, 2008).

Drill 1-Basic Skills in Nozzle Operation: The starting point in developing a high level of proficiency in nozzle use is to gain familiarity with the nozzle(s) you will be using including performance characteristics such as flow rate, operating pressure, and nozzle controls (i.e., shutoff, pattern, flow). In addition, firefighters should build skill in basic nozzle techniques such as the short pulse, long pulse, penciling, and painting while in a fixed position. Click on the following link to download the instructional plan for Drill 1 in PDF format.

Hose and Nozzle Technique Drill 1 Instructional Plan

Firefighting is team based. After firefighters have demonstrated individual proficiency in basic nozzle techniques from a fixed position, the next step is to apply these techniques in a team context.

Drill 2-Hose Handling and Nozzle Operation: Firefighters often lose focus on nozzle technique and operation when they are moving. This drill provides an opportunity for the firefighter with the nozzle and backup firefighter to develop a coordinated approach to movement and operation.

Drill 3-Nozzle Operation Inside Compartments: Deployment of hoselines inside a building requires a somewhat different set of skills than simply moving forward and backward. Movement of hoselines around corners and adjustment of nozzle pattern to cool gases in hallways and varied size compartments are important additions to the firefighters’ skill set and provide the next step in developing proficiency in nozzle use.

Drills 2 and 3 will be addressed in the next post in this series. Subsequent posts will address door entry procedures, indirect attack, and will introduce the concept of battle drills to build skill in dealing with worsening conditions or other emergencies while operating inside burning buildings.

Ed Hartin, MS, EFO, MIFIreE, CFO

References

Hartin, E. (2004). Theoretical foundations of fire service instructor training (unpublished manuscript available from the author). Portland State University.

Allen, C. R. (1919). The instructor the man and the job. Philadelphia, PA: J. B. Lippencott Company. Prosser, C. A., & Allen, C. R. (1925). Vocational education in a democracy. New York: The Century Company.

Schmidt, R. & Wrisberg, C. (2008). Motor learning and performance (4^th ed.). Champaign, IL: Human Kinetics.

Reigeluth, C. (1999). Elaboration theory: Guidance for scope and sequence decisions. In C.M. Reigeluth (Ed.) Instructional-design theories and models: A new paradigm of instructional theory volume II. Mawah, NH: Lawrence Erlbaum Associates.

Warfare is often used as a metaphor for firefighting with fire being the enemy and the building the ground on which we fight. Extending warfare as a metaphor, handline nozzles are firefighters’ principle weapon in offensive firefighting operations.

In the early 1940s Major General William H. Rupertus, United States Marine Corps (USMC), wrote the Rifleman’s Creed (also known as My Rifle). The creed is part of Marine doctrine that emphasizes that regardless of specialty or assignment, all Marines are riflemen. The Rifleman’s creed emphasizes the criticality of caring for and mastering the use of the Marine’s individual weapon. How many firefighters have the same commitment to care and mastery of their nozzle?

All too often, firefighters consider the nozzle to be a simple device requiring little practice to master and seldom thought of until needed. Take a minute and think about the nozzle(s) that you use!

Nozzle Knowledge

These 20 questions focus on some of the fundamental knowledge that firefighters must have if they are truly going to master their primary weapon in offensive firefighting operations.

1. What kind of nozzle(s) are on your preconnected hoseline (combination or solid stream)?
2. What type of nozzles are they (i.e., fixed flow, variable flow, automatic, or single tip, stacked tips)?
3. What flow rate, rates, or range do they have?
4. If flow rate can be varied, how is this accomplished? Does the mechanism used to change flow operate freely?
5. If you change the flow without a corresponding change in line pressure at the pump, what happens to the nozzle pressure?
6. What is their designed operating pressure or pressures (for dual pressure nozzles)?
7. For combination nozzles, what is the impact of nozzle pressure on droplet size? Can you operate the nozzle at more than one nozzle pressure?
8. If a variable flow or automatic combination nozzle, does droplet size change with flow rate? Why might this be significant?
9. What is the maximum effective reach of the nozzle?
10. Can you flush debris from the nozzle? If so, how?
11. What type of coupling is the nozzle equipped with (e.g., if threaded, is it National Standard Hose, Iron Pipe, or some other thread)?
12. What type of valve is the nozzle equipped with (ball or slide valve) and what difference does it make?
13. If it is a combination nozzle, does it have fixed or spinning teeth? Why would this matter?
14. If the nozzle is equipped with spinning teeth, does the turbine spin freely?
15. Do your nozzles open and close easily when under pressure?
16. Are your nozzles clean (inside and out)? How should they be cleaned?
17. Do your nozzles require lubrication to ensure free movement of their operating mechanism? If so, when was the last time that they were lubricated?
18. If a combination nozzle, how to you adjust the nozzle to a wide angle fog pattern?
19. For combination nozzles, what is the maximum angle of the wide fog pattern?
20. If a combination nozzle, how far from straight stream or wide angle fog does the pattern control need to be turned to produced a 40^o (medium) fog pattern?

While knowing the answers to these questions, is necessary, it alone is not sufficient. In addition to knowledge of operating characteristics and maintenance procedures, firefighters must be skilled in nozzle operation in order to be able to accurately put water where it is needed.

Nozzle Skills

In some respects a nozzle is a fairly simple device designed to increase the velocity of water and provide a useful stream for firefighting operations. However, can you consistently:

1. Adjust a fog pattern to the desired angle without visual reference, before opening the nozzle to check the pattern?
2. Apply a short or long pulse of water fog so that the droplets evaporate in the hot gas layer, minimizing water contact with compartment linings (i.e. walls and ceiling)?
3. Apply a fog pattern to fill the maximum volume of a compartment without excessive water hitting the compartment linings?
4. Apply water gently in the form of a straight stream so that it flows onto a hot surface, maximizing cooling and minimizing runoff?
5. Recognize audible indicators of fire stream impact on compartment linings?
6. Adjust flow rate based on conditions and tactical application (i.e. gas cooling, indirect attack, direct attack)?
7. Maximize both effectiveness (in controlling the fire) and efficiency (by minimizing water use)?

These questions are obviously focused on combination nozzles. If you more commonly use solid stream nozzles, ability to cool hot gases is limited by the form in which water is applied. While limited in gas cooling effectiveness, what techniques can you use to have some impact on the threat presented by the hot gas layer?

As with knowledge of your nozzle, these skills are necessary, but not sufficient. Firefighters must be able to integrate physical skill with situational awareness and team based tactical skill.

My Nozzle

With due credit to General Rupertus and the USMC; I have adapted The Rifleman’s Creed:

This is my nozzle, there are many like it but this one is mine. My nozzle is my best friend. It is my life. I must master it as I master my life. Without me it is useless, without my nozzle I am useless.

I will use my nozzle effectively and efficiently to put water where it is needed. I will learn its weaknesses, its strengths, its parts, and its care. I will guard it against damage, keep it clean and ready. This I swear.

Developing Skill

During structural firefighting operations firefighters are faced with dynamic and rapidly changing conditions in which situational awareness is critical. Basic skills in the use of personal protective equipment and the tools of the firefighters’ craft must have reached the autonomous stage of performance to allow focus on critical decisions and tasks.

Habit hardens the body for great exertions, strengthens the heart in great peril, and fortifies the judgment against first impressions. Habit breeds that priceless quality, calm, which passing from hussar and rifleman up to the general himself, will lighten the commanders task. (Von Clausewitz, p. 122)

Colonel B.P. McCoy, USMC (2007) drew on Clausewitz’s wisdom in identifying combat marksmanship as a critical habit. “Anybody, even in the middle of a phobic response to the violence of combat can yank on a trigger and spray rounds in the general direction of the enemy, ‘spray and pray'” (p. 25). How many firefighters have the same response in the fire environment? “Combat marksmanship is the hallmark of the infantryman. Nothing nurtures confidence like the knowledge that one can hit what one is shooting at” (McCoy, 2007, p. 25). Firefighters require the same skill in nozzle use as Colonel McCoy’s Marines required in the use of their rifles.

During offensive firefighting operations firefighters apply water for one of two purposes. 1) to cool hot gases or 2) to cool hot surfaces (Grimwood, Hartin, McDonough, & Raffel, 2005). Each of these tasks requires a different method to put water where it is needed in a form that will accomplish the intended outcome.

Gas Cooling: In general water application to cool hot gases should be based on the following requirements:

• Most of the water applied must vaporize in the hot gas layer (not on surfaces)
• Nozzle pattern should maximize the volume of hot gases cooled.

The challenge to the nozzle operator is that there is not one single approach to meeting these requirements. In general, smaller droplets work better than large droplets, but nozzle pattern (wide, medium, or narrow fog) is dependent on the size of the space and temperature of the flames and/or hot, unignited gases.

Surface Cooling: The requirement for cooling hot surfaces is different than those required for gas cooling, but is equally simple.

Most of the water applied must vaporize on contact with hot surfaces (not in the hot gas layer)

As with gas cooling there is not a single approach to meeting these requirements. In general, effective surface cooling requires a thin layer of water on the hot surface. If the surface is extremely hot, water application must be continued until the temperature is reduced sufficiently to slow and stop pyrolysis.

Important! Water on the floor after extinguishment is completed did not do significant work. Far more energy is required for water to change phase into steam than to simply raise its temperature. Water application must be effective (in achieving fire control), but should also be efficient (in minimizing the water used and limiting fire control damage).

Effective and efficient fire control requires that firefighters be skilled at putting water in the right form where it is needed (in the hot gases or on hot surfaces). Development of autonomous (habitual) skill in nozzle use requires deliberate practice. This is not simply repetition of our current skills, but continuing to stretch just beyond our current abilities. Deliberate practice is designed specifically to improve sharply defined elements of performance.

The next several posts in this series will examine how research in sport psychology regarding motor learning and performance can be used to enhance our ability to develop proficiency in nozzle use (as well as other physical firefighting skills).

Ed Hartin, MS, EFO, MIFireE, CFO

References

US Army (1992). Field manual 7-8 infantry Rifle platoon and squad. Washington, DC: Headquarters, Dept. of the Army.

Clausewitz, C. (1984) On war. (M. Howard & P. Paret, Trans.). Princeton, NJ: Princeton University Press

McCoy, B. (2007). The passion of command. Quantico, VA: The Marine Corps Association.

Grimwood, P., Hartin, E., McDonough, J, & Raffel, S. (2005) 3D firefighting: Training, techniques, and tactics. Stillwater, OK: Fire Protection Publications.

The previous post (Shielded Fires) examined US Navy research on the effectiveness of different nozzle techniques when dealing with shielded fires conducted on the ex-USS Shadwell, the US Navy full scale damage control research facility (see Figure 1).

Figure 1. USS Shadwell

The researchers tested two different methods for controlling flaming combustion overhead while moving from the entry point to a location in a compartment where firefighters could make a direct attack on the seat of the fire. The first method involved use of a straight stream or narrow fog pattern and the second involved the use of a medium (60^o) fog pattern directed upward at a 45^o angle. In both cases, one to three second pulses were used in application of water into the hot gas layer.

US Navy Findings

Analysis of this series of tests resulted in identification of a number of specific findings related to tactics, equipment, and training. Three of these findings were particularly relevant to the differences between straight stream/narrow fog and medium fog applied to control flaming combustion in the upper layer.

• Pulsed application with a medium fog pattern directed upward at a 45^o angle resulted in less disruption of the thermal layer than use of a straight stream/narrow fog pattern.
• Use of a straight stream/narrow fog resulted in production of a large amount of steam. This was attributed to the fact that the hose streams had to be deflected compartment linings.
• Water management is important when controlling fire in the upper layer, particularly when using a straight stream/narrow fog. Excess water will only result in excess steam production.

Discussing the findings, the researchers observed that pulsed application of medium fog appeared to be an effective tactic for controlling flaming combustion in the upper layer. This conclusion is supported by consistent reduction of upper layer temperature over the course of the tests involving use of pulsed application of a medium fog pattern.  Previous concerns that this approach would result disruption of thermal layering and excess steam production appeared to be unfounded. This conclusion is supported by the heat flux data at 0.9 M (7′ 10″) and 2.9 M (3′) above the floor. Disruption of thermal layering is indicated by an upward spike in lower level heat flux or equalization of heat flux at the lower and upper levels.

Questions

Several questions about the outcome of these tests were posed at the end of the Shielded Fires post.

• Why did the application of water in a straight stream/narrow fog pattern fail to effectively control flaming combustion in the upper layer?
• Why did the upper layer temperature fluctuate when a straight stream/narrow fog was used?
• Why did the upper layer temperature drop consistently when a medium angle fog pattern was used?
• How did the heat flux measurements correlate with the upper layer temperatures in these two tests?
• What are the implications of the heat flux data recorded during these tests on tenability within the compartment for both firefighters and unprotected occupants?

Water converted to steam on contact with compartment linings or other hot objects cools the surfaces. This indirectly lowers gas layer temperature as the hot gases will continue to transfer heat to compartment linings and other cooler objects in an attempt to equalize temperature. However, the effect on upper layer temperature is limited, minimizing effectiveness of stream application in controlling flaming combustion in the upper layer. In addition, as gas temperature is not significantly reduced, steam produced on contact with hot surfaces is added to the volume of hot gases, resulting in a less tenable environment.

Ineffectiveness of straight stream/narrow fog attack in controlling flaming combustion in the upper layer and the perception of increased steam production with this type of attack likely have a common cause. Conversion of water to steam requires much more energy than simply heating water from ambient temperature to its boiling point. When water changes phase from liquid to gas (steam) while in the hot gas layer, the temperature of the gases is reduced. This has several consequences. First, sufficient reduction in temperature results in extinguishment of flaming combustion. Second, reduction of gas layer temperature causes a proportional reduction in gas volume. As illustrated in Figure 2, if 35% of the water is truned to steam in the hot gas layer, the total volume of steam and hot fire gases is less than the original volume of hot fire gases alone (Särdqvist, 2002). As this is often difficult to understand, I will provide a more detailed explanation of this in a subsequent post.

Figure 2. Gas Temperature and Relative Volume

Note. Adapted from Water and Other Extinguishing Agents (p. 155) by Stefan Särdqvist, 2002, Karlstad, Sweden: Raddningsverket. Copyright 2002 by Stefan Särdqvist and the Swedish Rescue Services Agency.

Production of the same volume of steam can have far different consequences depending on where it is produced (in the hot gas layer versus on contact with hot surfaces!

Total heat flux includes energy transferred through radiation, convection, and conduction. However, in these full scale fire tests, radiant and convective heat transfer was most significant. Radiant heat transfer is dependent on the temperature of upper layer gases and flaming combustion. Convective heat transfer is dependent on gas temperature, movement of hot gases, and moisture. Reduction in upper layer temperature while maintaining thermal layering minimizes total heat flux at the lower level where firefighters are working.

Other Considerations

These tests were conducted on a ship (see Figure 1) with most of the compartment linings being metal (rather than gypsum board, plaster, or wood as typically encountered in buildings. The fire compartment did not have windows or other ventilation openings that may exist in more typical buildings encountered by structural firefighters. These differences are significant, but do not diminish the importance of the results of these tests and findings by the researchers.

These tests provide substantive evidence in support of the effectiveness of water converted to steam in the hot gas layer (as opposed to on surfaces) in controlling flaming combustion in the hot gas layer. However, this does not diminish the importance of direct application of water onto burning fuel in a direct attack to complete the process of extinguishment.

Reference

Särdqvist, S. (2002). Water and other extinguishing agents. Karlstad, Sweden: Swedish Rescue Services Agency.

Scheffey, J., Siegmann, C., Toomey, T., Williams, F., & Farley J. (1997) 1994 Attack Team Workshop: Phase II-Full Scale Offensive Fog Attack Tests, NRL/MR/6180-97-7944. Washington, DC: United States Navy, Naval Sea Systems Command

Remember the Past

In Myth of the Self-Vented Fire I pointed out that every week represents the anniversary of the death of one or more firefighters as a result of extreme fire behavior. Some firefighters have heard about these incidents, but many have not. In an ongoing effort to encourage us to remember the lessons of the past and continue our study of fire behavior, I will occasionally be including brief narratives and links to NIOSH Death in the Line of Duty reports and other documentation in my posts.

February 11, 1998 – 1030
Firefighter Paramedic Patrick Joseph King
Firefighter Anthony E. Lockhart
Chicago Fire Department, Illinois

Firefighter King and Firefighter Lockhart responded on different companies to a report of a structural fire in a tire shop. No visible fire was encountered, there was no excessive heat, and only light smoke was found in most of the building with heavier smoke in the shop area. Ten firefighters were in the interior of the structure when an event that has been described as a flashover or backdraft occurred. The firefighters were disoriented by the effects of the backdraft. Some were able to escape but Firefighter King and Firefighter Lockhart were trapped in the structure. A garage door that self-operated due to fire exposure may have introduced oxygen into the fire area and may have been a factor in the backdraft. The exit efforts of firefighters were complicated by congestion in the building. Within minutes of the backdraft, the building was completely involved in fire and rescue efforts were impossible. Both firefighters died from carbon monoxide poisoning due to inhalation of smoke and soot. Further information related to this incident can be found in NIOSH Fire Fighter Fatality Investigation 98-F-05.

February 9, 2007
Firefighter-Paramedic Apprentice Racheal Michelle Wilson
Baltimore City Fire Department, Maryland

Firefighter Wilson and the members of her fire academy class were attending a live fire training exercise in a vacant rowhouse in Baltimore.

Firefighter Wilson was assigned to a group of apprentices and an instructor designated as Engine 1. Her group advanced a dry attack line into the structure. As they climbed the stairs, the line was charged. Engine 1 encountered and extinguished fire on the second floor but did not check the rest of the second floor for fire prior to proceeding to the third floor. On the third floor, they again encountered and began to extinguish fire.

Fire conditions began to worsen with a marked increase in smoke and heat that appeared to be coming from the second floor. Engine 1 firefighters who were on the stairs began to receive burns from the fire conditions. The instructor for Engine 1 climbed out a window at the top of the stairs and helped one burned firefighter escape to the roof.

Firefighter Wilson appeared at the window in obvious distress and attempted to escape. The windowsill was unusually high (41 inches) and she was unable to escape. Firefighter Wilson momentarily moved away from the window, at which time she advised other firefighters to go down the stairs to escape. When she returned to the window, her SCBA facepiece was off and she was beginning to receive burns. She was able to get her upper body out of the window but she could not make it through. Firefighters on the exterior were unable to pull her through until firefighters were able to gain access on the interior and assist with the effort.

When Firefighter Wilson was pulled to the roof, she was in full cardiac and respiratory arrest. She was immediately removed from the roof and received advanced life support care and transportation to the hospital. She was pronounced dead at 1250 hours. Firefighter Wilson received total body surface burns of 50 percent. The cause of death was listed as thermal burns and asphyxiation.

Further information related to this incident can be found in NIOSH Firefighter Fatality Investigation F2007-09 and the Independent Investigation Report on the Baltimore City Fire Department Live Fire Training Exercise, 145 South Calverton Road, February 9, 2007.

My next post will examine the incident in which Rachael Wilson lost her life in greater detail.

Ed Hartin, MS, EFO, MIFIreE, CFO