By Nick Peppard
The United States Marine Corps teaches new Marines going through basic training a creed known as “My Rifle.” This famous creed emphasizes the importance of knowing their weapon inside and out.
It drives home the importance of being intimately familiar with the inner workings of their rifle and the necessity of thorough inspections and maintenance. The rifle is their lifeline and, as such, they must become masters of its use.
The movement of water from a supply source through a fire engine’s pump and out the end of a fire hose and nozzle assembly to deliver a usable, sufficient, and effective fire stream is, at its core, the essence of engine company work. Much as the Marine Corps places high levels of importance on Marines being competent, confident, and masters of their weapons, so too must the fire service place the same attention to detail on the weapons of our warfare. Ineffective pressure, volume, or both; unmanageable nozzle reaction; and poor attack line performance and management can have negative consequences on the firefighters operating them and can spell disaster in our efforts to save lives and property. But, have you ever considered what goes into designing effective fire attack packages? As the saying goes, “The devil is in the details.” This article will examine these components and how to implement them as part of an attack package.
WEAPON SELECTION
Engine firefighters and officers must be well versed with the weapons at their disposal. While we all likely have our preferences for nozzle sizes, types, and brands, many of us are not in a place to dictate what is actually on our assigned apparatus. This leaves us two choices: We can make excuses for poor performance because we lack the ideal nozzles, hose, equipment, etc. or we can learn as much about our attack packages as possible to make the most of what we DO have and advocate for positive changes when opportunities present themselves by way of education and suggestions.
Sure, most have their own opinions as to what is the best hose/nozzle combination, apparatus configuration, hose load, adapters, etc. Hopefully, those opinions are well researched and thought out and not just regurgitated based on what our favorite firefighter, officer, or instructor touts. The truth is it is a package deal. Hose and nozzle construction and design absolutely impact performance. For example, if you were to take a 100-pound-per-square-inch (psi) automatic fog nozzle and a 50-psi ⅞-inch smooth bore, each flowing 160 gallons per minute (gpm), you’d have to contend with 30 pounds more nozzle reaction and a 50-psi higher pump discharge pressure right off the bat with the fog nozzle. All other components being equal, this places extra work on the hose team by default as they must manage more reaction force. It also makes our apparatus work harder to achieve equivalent flows.
Additionally, all hose is not created equal. But, don’t take my word for it. Do your own research and you’ll find that even from the same manufacturer, there are considerable differences in target flow ranges, internal diameter, liner construction, and friction loss, just to name a few. One hose manufacturer has hose where there is a 20-psi difference in friction loss in a 200-foot crosslay between one of its more budget-friendly hose specifications and one of its higher end hoselines. Some variances are even greater! How can this be? The answer is multifaceted. Liner design, materials, true internal diameter/diameter creep, and target flow ranges all play into the equation.
But, before we get into hose construction, let’s take a quick look at diameter creep. The push for greater fire flows has led to true hose internal diameter increases. Thus, the actual internal size of the hoseline once charged and pressurized with water compared with the size it is marketed at is often quite different. For example, many are surprised to find out that their 1¾-inch hose is actually closer to 2-inch hose once charged. Many 1¾-inch hoselines are actually 1.77, 1.78, 1.88, or even 1.9 inches when charged. While some may initially think that more is better, this is not necessarily true. With the increased internal diameter, there is certainly more water. However, at 8.35 pounds per gallon, that extra water translates into more weight for the engine crew to drag, which in turn means crews reaching fatigue sooner.
Additionally, as many have taken to the mindset of more is better, they have also increased handline flows by either overpumping the hoseline or increasing the nozzle orifice size. This extra water is good from an extinguishment standpoint but also creates more reaction force (nozzle reaction) for the hose team. The late Fire Department of New York Lieutenant Andrew A. Fredericks conducted several experiments that identified the ideal reaction force for the average firefighter is around 70 pounds for one firefighter and 100 pounds for two firefighters.
Remember, in most rural, suburban, and even many urban systems, the initial attack line may only be staffed with two personnel (an officer and a firefighter) as the driver/engineer is pumping the apparatus and doing “outside” functions. In a well-developed fire, it does no good if the firefighter must keep shutting down the nozzle because the reaction force is too high and is hard to manage. Furthermore, if the crew has difficulty advancing the line because of extra weight and reaction, the line may not reach the seat of the fire in a timely fashion, allowing the fire to grow.
HOSE CONSTRUCTION
There are three primary methods of liner construction:
- Ethylene propylene diene monomer (EPDM), a synthetic rubberized material.
- Extruded through-the-weave.
- Polyurethane.
Hose with EPDM liners is manufactured by pulling a synthetic rubber liner through a fabric jacket and bonding them together with an adhesive and application of steam.
Hose with extruded, “through-the-weave” liners is manufactured by applying a liquid form of a rubberized material to a tube of a fabric, such as polyester. The liquefied rubberized material is impregnated within the weave by forcing it through an extruding machine, which creates a tubular liner.
Hose with polyurethane liners is sometimes marketed as “high-rise” hose because it is lighter than the EPDM and through-the-weave counterparts. However, the light weight may have been achieved by sacrificing thermal and abrasion resistance. Because of the lack of durability, some fire departments only use it for high-rise/standpipe operations.
1 A properly specified hose and nozzle assembly in conjunction with well-trained firefighters work in harmony to achieve the objective of rapid fire suppression. (Photos by author.)
THE FREEMAN RATIO
As we continue our review, we must understand that there is a correlation between internal hose diameter and the nozzle orifice itself in regard to attack line performance. There is a scientific principle known as the Freeman ratio. This principle states: “The ideal nozzle tip size is one in which the internal diameter of the tip is at or less than one half the internal diameter of the hoseline to which it is attached” (Brumley, 2021). The goal is for the water to accelerate. Thus, to get the best performance out of your attack package, the nozzle must pair up with the hose. They are not independent of each other but are rather directly related to the performance of the handline and the fire stream produced. If the nozzle diameter is too large for the hoseline it’s attached to, it will be more prone to kinking or “nozzle whip.”
For example, a 15⁄16-inch smooth bore nozzle has an orifice size of 0.9375 inch. Thus, if you double the orifice size, it would equal 1.88 inches. Thus, a 15⁄16-inch smooth bore nozzle will perform best when it is attached and flowing from a hose with an internal diameter of 1.88 inches.
A ⅞-inch smooth bore has a decimal orifice size of 0.875 inch, which, if doubled, equals 1.75 inches. So, we can see that the ⅞-inch smooth bore is best suited for a hoseline with a true 1.75-inch internal diameter (Freeman, 2012).
Now, per the Freeman ratio, we can certainly pair the ⅞-inch nozzle on the 1.88-inch hose and still have decent results, although the hose will hold more water, making it heavier than a 1.75-, 1.77-, or 1.78-inch internal diameter hose. However, putting a 15⁄16-inch or larger orifice nozzle on a 1.75-inch internal diameter hoseline will yield a hoseline with more of a tendency to have nozzle whip.
Furthermore, placing low-pressure nozzles on hose designed for higher-pressure nozzles will have equally poor performance results. As a young firefighter, I recall being excited to finally get a 15⁄16-inch smooth bore nozzle to use on our engine companies. I eagerly placed it on our 1¾-inch hose bundle and set out to show the supremacy of the new smooth bore nozzle! We flaked it out, charged it to the correct nozzle pressure of 50 psi, and opened the line. I couldn’t figure out why we struggled with nozzle whip and kinking so badly. This left many questioning the effectiveness of the new nozzle that I had been hyping for months. Some immediately wrote it off as being too hard to handle. I wanted answers. I began taking more engine classes, reading as many engine texts, articles, and manuals as I could find. It wasn’t long before I was introduced to the Freeman ratio and the importance of pairing the nozzles and hoselines appropriately. I came to realize the problem wasn’t the nozzle in and of itself but rather the hoseline it was attached to, as we did not have premium hose constructed for high volume/low nozzle pressures.
The goal with this portion of the article is not meant to muddy the water but to draw attention to the fact that our attack packages are just that: packages. As such, each agency must determine its needed target flows, normal staffing on a handline, acceptable nozzle reaction thresholds, hose load configurations, and budgetary constraints. Ultimately, each department should do everything in its power to properly equip its firefighters with a well-thought-out, systematically assembled hose/nozzle attack package that gives it the desired flows while allowing mobility and reaction forces that ITS staffing levels can handle without having to constantly shut down or reposition. It does no good for a department with an average of two firefighters on a given handline to try to pattern its attack packages after a department that has an average of four or more firefighters on the same attack line.
HOSE LOAD CONSIDERATIONS
Many fire departments use preconnected hose loads for their primary method of extinguishing the lion’s share of their fires. There are a number of configurations available for preconnected handlines. From side- and top-configured preconnected handline troughs to pull-out speedlay trays to rear-configured hosebeds of varying heights and setups, there are certainly many options for departments to choose from when spec’ing their pumping apparatus. Of course, there are also bulk beds and hose bundle configurations in addition to preconnected handlines, but for the sake of time we will primarily discuss preconnected hose loads here.
FLAT LOAD
The flat load is one of the oldest (if not the oldest) hose loads in the American fire service. Its simplicity in both loading and deployment and its ability to be modified to suit the user’s needs make it a popular choice in many departments. Most preconnected flat loads feature some sort of length identifiers/pull loops and are typically finished with the nozzle on top of the hose load. Some may load it back and forth in a similar fashion to how large-diameter hose (LDH) is loaded, while others choose to stack it in neat vertical stacks. Others have opted to finish the last 50 to 100 feet in a bundled fashion with hose straps keeping the finished bundle together until the nozzle firefighter is ready to deploy the bundled hose. Proponents of the flat load tout its simplicity and ability to be pulled like a triple layer or minuteman hose load when loaded and deployed correctly. Those who aren’t fans of the flat load for preconnected attack lines argue that if the flat load needs to be modified to be deployed like another hose load, then why not just use those other loads to begin with? Another argument against the flat load is that it ends up being more of a hose “drag” than “shouldered” load in many configurations.
MINUTEMAN
The minuteman hose load, and modifications thereof, is a very popular hose load for several reasons. It is a “shouldered” hose load and allows for the nozzle firefighter to get the entire working length of hose off the ground, thus creating less friction and fewer pinch points. Furthermore, the minuteman hose load allows firefighters to clear obstacles and navigate stairs easier than hose “drags” because of the working length (often 100 feet) being on the firefighter’s shoulder until the time it needs to be flaked out. Many have modified the original minuteman load by only shouldering half the preconnected load. Others have added hose straps and pull loops to the shouldered portion of the load to create a “bundled” hose load. This helps keep the working length together until the firefighter reaches the drop point and deploys it.
TRIPLE LAYER
The triple layer load is the newer of the above-mentioned hose loads and became popular, particularly in the suburban fire service, with the advent of speedlays and transverse, preconnected hosebeds. The load is essentially a big “S” that is designed to deploy the entire length of the preconnected hose load in one-third the length of the hose. So, a typical 200-foot crosslay would clear the hosebed in approximately 66 feet. The triple layer is a hose “drag” rather than a “shouldered” load, so it doesn’t do particularly well with many obstacles to navigate. Stairs also take extra leg work to deploy the line up. In the suburban setting where houses are often uniformly spaced and have similar setbacks over 50 feet from the street, this load excels. This once very popular load has lost favor in recent years in many agencies, as departments have returned to more traditional “shouldered” loads that better suit their jurisdictions and give them better tactical options on the fireground.
BUNDLED LOADS
There are numerous variations of hose bundles. From the popular “Gustin Pack” named after Miami-Dade (FL) Fire Department Captain and national fire service instructor Bill Gustin to more regional bundles like the “Wichita Bundle,” the “Detroit Bundle,” the “Cleveland Load,” and the more generalized “flat” and “modified minuteman” bundles, there are certainly plenty of options for students of the job to choose from when evaluating bundled hose loads for their jurisdiction. Regardless of which “bundle” you choose, the concept is relatively the same: A bundled load (of a predetermined length) is attached to a static or preconnected hose load (often in a variation of the flat load). Sometimes the bundles are used as part of a preconnected attack package. Other times, the bundle is used to extend a line or when performing a “courtyard stretch” (2½-inch or larger trunk line supplying two or more smaller diameter attack lines) requiring longer hoselays.
2 Sometimes bundles are used as part of a preconnected attack package. Other times, the bundle is used to extend a line or when performing a “courtyard stretch” requiring longer hoselays.
ENERGY, ENERGY ABSORPTION, AND THEIR IMPACT ON HOSELINE SELECTION
As part of our size-up we must also consider some of our generalized “knowns.” For example, recent research conducted by the National Institute of Standards and Technology (NIST) has shown that our modern residential fuel load equation for determining energy output in typical residential homes is 0.07 megawatts (MW)/per square foot (ft2) (Vestal & Bridge, 2010). This formula allows us to quickly gather a rough estimate and choose a line that best suits our needs. For example, a 10- × 10-foot bedroom fire would produce 7 MW when fully involved. So, that being said, if I had three similarly sized bedrooms on fire, I would anticipate an energy release of approximately 21 MW.
We also know from research that it only takes 1 to 2 MW, 1,112°F at the ceiling, and/or a heat flux of 20 kW/m2 to produce flashover conditions (Vestal & Bridge, 2010). That said, we must also understand the concept of thermal rebound and what it means to engine companies engaging the fire. Thermal rebound occurs when we briefly apply water to cool the space temporarily. However, if we do not apply adequate water to the seat of the fire, we will see the heat rapidly begin to build again once we shut our nozzle down. This can be the case during a transitional attack where we apply water from a window for 15 to 20 seconds, shut it down, and then prepare to move to the interior for fire attack. If we do not get a line in position and flowing water very shortly after shutting the line down, we will see fire retake the space we previously cooled. This can also occur on interior fire attacks where the nozzle firefighter shuts down the nozzle deliberately or nondeliberately (excessive nozzle reaction, poor hoseline performance, or poor technique). Either way, the moment we stop cooling the environment, we allow the heat and pressure gradients to shift back toward our position and risk losing the firefight or, worse, causing civilians or firefighters to be exposed to greater thermal insult than if we continuously cooled the environment with the reach of our hose stream as we advance.
3 Firefighters build a Denver high-rise hose pack.
STREAM APPLICATION: PUTTING IT ALL TOGETHER
There are scores of different nozzles available in today’s fire service market. However, when it comes to structural firefighting, they can typically be lumped into one of four categories: smooth bore, fixed gallonage fog, adjustable gallonage fog, and automatic fog.
We must understand the pros and cons of our nozzles and how they impact our fire streams. Smooth bore nozzles have larger drops, thus creating more reach and penetration than their fog nozzle counterparts. They have a 50% heat absorption capacity, whereas fog nozzles have an approximately 75% heat absorption capacity (Vestal and Bridge, 2010) because of their smaller droplets, which equals more droplet surface area. For some basic points of reference, a ⅞-inch smooth bore and 15⁄16-inch smoothbore can absorb 24 MW and 27 MW, respectively, and a 150-gpm fog and a 180-gpm fog can absorb 33.8 MW and 40.6 MW, respectively (using the NIST formula of 0.3 MW/gpm × 50% for smooth bore and 75% for fog) (Vestal & Bridge, 2011).
Heat absorption capacity is only one part of the equation. One must consider all factors impacting water application to be best informed. The water can only absorb the heat producing energy emitted by the burning fuels if it can physically reach the burning fuels.
NIST researchers found that with fog streams, “Seventy-five percent of the droplets will evaporate at the ceiling, 12.5% will fall to the floor, and 12.5% will be caught in the thermal column.” Conversely, with smooth bore streams,“Forty percent of the stream evaporates at the ceiling, 55% of the stream falls to the floor, and 5% is trapped in the thermal column.” (NIST, 1992) Thus, while the fog nozzle may be more efficient at energy absorption, it is often less effective at reaching the seat of the fire to effect extinguishment compared with the smooth bore nozzle.
Further, research indicates that at flashover temperatures, the fog may not reach the burning fuel surfaces at all and, in fact, evaporates at heights of 5 feet from the floor (Grimwood, 2006). NIST corroborated Grimwood’s findings in 2009 and went on to show that the solid stream (not to be confused with fog nozzle’s straight stream) reduced heat release rates (HRR) 20 seconds faster than fog streams (NIST, 2009).
Additionally, when speaking to firefighters around the country, there is a misconception among some fire departments that two smaller 1¾-inch handlines equate to or exceed the knockdown power of a larger 2½-inch handline. This thinking is somewhat skewed. Yes, you may be flowing equivalent or even slightly greater volume, but what you lack is concentrated stream mass, energy, and reach. The larger caliber stream produced by a 2½-inch handline flowing 250 to 328 gpm offers more concentrated extinguishing power to knock down large bodies of fire easier than two smaller handlines. It has a larger stream delivering larger amounts of water with larger droplets over greater distances. It’s why we use master streams on defensive fires instead of five or six small-diameter attack lines.
Allow me to use another combat analogy. It’s why our military uses midlevel artillery instead of throwing more 5.56 cal. bullets at heavily fortified and armored enemies. No one would argue the knockdown power of a .45 caliber handgun vs. say a .38 caliber handgun. The same principles apply to our fire streams. If our “enemy” is larger than what can be easily handled with our “infantry” (i.e., 1¾-inch hoselines), then it’s time to consider our midlevel artillery (2- to 2½-inch hoselines) to knock back the fire to the point our firefighters can make entry with smaller lines for final extinguishment. Furthermore, if the fire is so large or intense that our medium-diameter hoselines cannot achieve the knockdown we need, it is time to break out our long-range, high-impact weapons (i.e., portable and fixed large-caliber streams).
Training Chief Brian Brush from the Midwest City (OK) Fire Department wrote an article for Fire by Trade called “Fire Streams and the Exponential Engine” (Brush, 2015). In it, he outlined a really great way to look at which attack package we select for the firefight. If it’s a 1¾-inch fire, we are looking for target flows of around 150 to 160 gpm. If the fire or fire building warrants a 2½-inch handline, our target flows should be approximately 300 gpm. And if the fire calls for a deck gun, we should be delivering a target flow of roughly 600 gpm.
His concept was that we should essentially double our flow rate with each increase in weapon selection. If we are going to take that next step up in “fire power,” so to speak, let’s make it worth our while. I agree. It does little good to go from flowing a 1¾-inch handline equipped with 15⁄16-inch smooth bore nozzle flowing 185 gpm to a 2½-inch handline equipped with a 1-inch tip flowing 210 gpm. You gain very little relative gpm to knock down the fire but gain all the added weight of the larger handline and increased nozzle reaction instead. This begs the question: “Is the juice worth the squeeze?” If we need “big” water, we must ensure that it’s in a volume sufficient to combat the HRR we are encountering on the fireground.
MASTER YOUR ATTACK PACKAGE
The above discussion on hose construction, nozzles, and hose loads is far from exhaustive, and there are numerous articles dedicated solely to each respective topic. As I mentioned earlier, many of us don’t have the ability to change what hose, hose loads, and nozzles are on our rigs. Thus, it is imperative that we fully understand the capabilities and limitations of our equipment with the intent of maximizing our potential to positively impact the fireground with what we have at our disposal. Engine companies should choose the most effective tools for the respective job.
Understanding factors impacting our attack line/nozzle selection is only half the battle, as it solves the “when” and the “why” components of the equation. Though being knowledgeable and well equipped is important, we must understand and be proficient in the “how” if we are to truly be effective at our jobs. For example, we may understand that a large, well-developed fire consuming the majority of a residential floor calls for pulling the 2½-inch handline with a target flow of 250 gpm or greater. However, knowing how to do something and being good at it are not the same thing. Skill acquisition takes intentional effort and repetition.
We must hone our knowledge and our skills collectively. A properly specified hose and nozzle assembly in conjunction with well-trained firefighters work in harmony to achieve the objective of rapid fire suppression. Firefighting is hard work. Firefighters need to focus on fighting the fire, not their attack package.
REFERENCES
1. Brumley, J. (2021, July 1). Big Considerations for Medium-Diameter Hoseline Purchases. Fire Apparatus & Emergency Equipment. https://emberly.fireapparatusmagazine.com/fire-apparatus/big-considerations-for-medium diameter-hoseline-purchases/#gref.
2. Freeman, J. R. (2012). Fire Stream Tables for Use of the Inspectors of the Associated Mutual Insurance Companies. Ulan Press.
3. Vestal, J. N., & Bridge, E. A. (2011, January 1). A Quantitative Approach to Selecting Nozzle Flow Rate and Stream, Part 2. Fire Engineering, 164(1). https://www.fireengineering.com/firefighting/a-quantitative-approach-to-selecting nozzle-flow-rate-and-stream-part-2/.
4. UL FSRI. (2017, July 25). Impact of Fire Attack Utilizing Interior and Exterior Streams on Occupant Survival, Part II. UL Fire Safety Research Institute. https://fsri.org/research-update/fsri-releases-part-ii-fire-attack-study-air-entrainment.
5. National Fire Protection Association. (2018). NFPA 1964, Standard for Spray Nozzles and Appliances, 4.1.5(2018 Edition). Retrieved June 15, 2023, from https://catalog.nfpa.org/NFPA-1964-Standard-for-Spray-Nozzles-and-Appliances P1477.aspx?icid=D729.
6. Vestal, J. N., & Bridge, E. A. (2010, October 1). A Quantitative Approach to Selecting Nozzle Flow Rate and Stream, Part 1. Fire Engineering, 163(10). https://www.fireengineering.com/firefighting/a-quantitative-approach-to-selecting nozzle-flow-rate-and-stream-part-1/.
7. NIST. (1992). In User’s Guide for the Fire Demand Model; A Physically Based Computer Simulation of the Suppression of Post-Flashover Compartment Fires (NIST GCR-92-612). Gaithersburg, MD: U.S. Dept. of Commerce.
8. Grimwood, P. (2006). A Comparison of 3D Water-Fog versus Straight Streams, using ‘Burst and Pause’ Cycles to Cool & Inert Dangerous Fire Gases in the Overhead of a Compartment Fire. High-Rise Firefighting. https://www.highrisefire.co.uk/docs/3D%20GAS%20COOLING.pdf.
9. NIST. (2009). Fire Fighting Tactics Under Wind-Driven Conditions: Laboratory Experiments. In (p. 335). NIST Technical Note, Gaithersburg, MD: U.S. Dept of Commerce.
10. Brush, B. (2015). Fire Streams and the Exponential Engine. Fire by Trade. https://countyfiretactics.com/wp-content/uploads/2021/08/Fire-Streams-and-the Exponential-First-Due-Engine-Company.pdf.
NICK PEPPARD is an 18-year firefighter/paramedic with the Oshkosh (WI) Fire Department and has numerous certifications and degrees. He is co-founder of the Rust Belt Jakes, president of the North Florida Fire Expo, training chair with the Old-Fashioned F.O.O.L.S., and co-host of the Make Due: Suburban Fireman Podcast.
