Rod Carringer

Tactical Advance

Published:  03 June, 2015

F&R Q2 TASTER: Task Force Tips’ Rod Carringer shares his perspective on nozzle performance with Class A foam solutions in different tactical situations during structural firefighting scenarios.

The use of Class A foam agents as an enhancement to initial attack fire flows often leads to a review of handheld nozzles to determine how to gain additional effectiveness and flexibility during structural attack. The problem is often these decisions are made without a complete understanding of operational needs. Before we delve into the world of application tools, it is imperative to accept some of the benefits and limitations of Class A foam agents as we integrate their use into operational guidelines.   

•            Class A foam is an enhancement to, not a replacement for, water.  All that we have learned about the required fire flows and critical application rates must be held as the baseline for suppression tactics.

•             Class A foams are not designed to effectively suppress the vapours of a flammable liquid. Much like water, the finished foam made with Class A concentrates may knock down a flammable liquid fueled fire, but post fire security is absent. If there is a source of ignition, expect a re-ignition of vapours even with a visible foam blanket on the spill.

•             Even a 0.1-0.2% injection of Class A concentrate (soap) into our fire flows provides amazing knockdown performance by simply reducing the surface tension of the water. The low cost solution soaks easily into deep seated fuels, clings to hot surfaces more effectively absorbing heat, and when expanded, offers a level of smothering or thermal insulation during exposure protection.

Before we look at nozzle choices, we now have some basic facts to use as a foundation for our assessment. Tactically, we will maintain needed and target fire flows; we will use the foam for Class A combustibles only; and we will take advantage of the soaking and penetrating characteristics of the finished foam to make our efforts more effective.

 Next, as we build upon this foundation, we need to understand the importance of how different finished foams (aspirated or solution) perform in the structural firefighting environment. We are adding foam concentrate (from 0.1% up to 1%) to our water through either a direct injection system, an eductor, or simply by batch mixing in our tank and providing a foam solution at the nozzle. Now, the next tactical opportunity presents itself. Sometimes the firefighter only requires 'wet' water to soak, other times a wet soaking low expansion finished foam to coat and cling and drain its moisture into the fuel beneath is needed, and other times it is important to have highly aspirated foam that will help to smother, insulate, or reflect radiant heat while protecting an exposure. While we all enjoy seeing lots of dry long lasting bubbles being made, tactically on a smoldering couch, blown in cellulose insulation, or a burning hay bale it isn’t the right tool for the job. From a training standpoint it becomes an important action to educate the initial attack teams on the performance aspects of the finished foams and how to make the best choice for the task at hand.

Finally, before we move on to nozzle choices, there are several key performance characteristics of foam concentrates that ultimately can and will affect the finished foam performance the crew expects from the nozzle. Once understood, tactical actions can be taken to enhance or improve the final performance.

•             Foam concentrates (in the bucket) come from many sources. Find and use foam that offers certification for acceptable environmental performance, provides outstanding bubble production throughout a range of fire ground criteria, and gives the best return on investment (not always the cheapest).

•              Water quality affects finished foam performance. The harder or mineral laden the water, the harder it will be to make lots of bubbles.

•             Temperature affects finished foam creation and longevity. The colder it is (air and water temperature) the harder it will be to make consistently long-lasting foam.

•             The injection percentage choice, typically from 0.1% up to 1%, may be varied to achieve the type of finished foam desired for your application. Lower injection percentages up to 0.3% are ideal when just a wet soaking application is desired. Up to a 0.5% application will increase the potential to make more bubbles, and at 1% not only can you generate more bubbles, but with more soap in the bubble skeleton, it will last longer.

 To summarize at this point, if you buy high quality foam, have soft water, nice warm temperatures, and turn your injection up to 1%, it is likely you will always make great amounts of bubbles. For the rest of us we need to adjust according to our environmental and operational limitations. Using Class A foam in structural firefighting is not an exact science, and understanding all of the factors that can affect finished foam performance will ultimately lead to making good tactical choices.

The next fork in the road are the application methods. A high-energy delivery system, such as Compressed Air Foam System, may incorporate an on-board air compressor system, or a low-energy delivery system that will use the energy of the pressure (velocity) in the line to make finished foam at the nozzle tip. Both are Class A foam delivery systems, yet each has very unique equipment requirements, operational constraints, and training needs.

High-energy systems, such as CAFS, rely on both the energy of air flow/pressure injected at the apparatus and the scrubbing of the homogenous foam mix as it travels down the attack hose line to provide a long lasting very consistent bubble structure. From a nozzle delivery standpoint, anything that is done internally to direct, shape, or straighten the fire stream typically tends to strip out some of the bubble structure turning the stream into much ‘wetter’ foam. As discussed earlier, tactically there is always a need to have a wetter more soaking foam to get into those deep seated fires and a combination nozzle on a high-energy system will accomplish that but for dry foam, an appropriately sized smooth bore tip does much better when a ‘drier’ foam structure is desired.

When using a high energy system for Class A foam operations, a two-piece nozzle offers the most versatility. The combination nozzle (fixed, selectable or automatic) will provide wet soaking foam, and has the straight stream and fog pattern capabilities necessary for interior suppression tactics. When dry foam is needed for applications such as exposure protection or pretreatment of fuels, removing the combination nozzle and using the integrated (and unrestricted) smooth bore provides maximum foam aspiration, reach and longevity.

The other fork in the road are low-energy or nozzle-aspirated foams; for most structural firefighters these are little more than a variation of the foam equipment and tactics we employ during Class B foam operations. By its basic waterway design, a standard combination nozzle provides great reach and penetration as well as a wide protective fog pattern, but little in the way of foam aspiration. From an initial attack standpoint though, this is ideal with the wet-soaking foam providing better suppression and elimination of rekindles than ‘water only’ applications.

If the tactical need for wetter foam providing both smothering and soaking capabilities is critical, a  low-expansion attachment offers the easiest and most cost effective method. Additionally, the low expansion tip is quickly removed, even during initial attack, to allow for a wide protective fog pattern if needed. From a stream performance standpoint, while you can expect an increase in foam aspiration, a decrease in reach and penetration will also be realized. In all low-energy finished foam or nozzle-aspirated applications, the energy being used at the nozzle tip can be easily characterised as a sliding scale from maximum reach and penetration at one end to maximum foam expansion at the other. The available energy will be used in some manner to provide the required foam expansion for the tactical need.

At the far end of this sliding scale is the medium or multi-expansion foam attachment. From a performance standpoint it maintains the same flexibility as the low-expansion attachment because it is easily removed from – or added to – the combination nozzle during operations based on tactical foam expansion needs. The multi-expansion attachment, being larger in size to allow for more air entrainment into the fire stream, often includes an integrated screen to enhance aspiration even more. Tactically, reach will be very limited, often only 5-6m, but expansion ratios of the finished foam may be substantial, up to 35:1 in many cases.

Having discussed many of the aspects of foam applications only one component is still needed to integrate Class A foam into operational guidelines – safety. Water with foam does react differently in the firefighting environment. Following are some initial observations that do require consideration during training.

•             While water’s high surface tension often makes fire streams less than effective by simply draining away, the injection of Class A foam and the corresponding reduction of surface tension found in the solution adds water weight to places often unnoticed. Dropped ceiling tiles, drywall, furniture, cellulose insulation will all now hold water and weight that in the past would have been shed. Increased weight brings with it a higher probability of the building infrastructure coming down on an interior crew. With 1 kg/l now soaking into and being held in fuels, additional vigilance needs to take place.

•             Class A foams are designed for Class A combustibles, and Class B foam such as AFFF and AFFF-AR are designed chemically for flammable liquids.

•             The use of Class A foam in an interior structural attack often leads to foam solution or bubbles getting on an SCBA face piece. Natural instinct in the heat of battle is to wipe it off with a dirty leather glove. The results are a black foaming mess that truly inhibits vision during an operation.

•             Bubbles visually conceal what is beneath them. Holes, debris, and uneven footing will all be hidden under the foam blanket. Step cautiously. Also, foam on tile floors, smooth concrete, or wood floors can also be a challenge with rubber-soled boots. Again, step cautiously.

•             Mother Nature is very clear about required fire flows. If more BTUs (British Thermal Units) are being generated in a fire space than you can provide water or solution to absorb usually the fire will not go out. Foam has little effect on the formulas for initial attack fire flows. It is an enhancement, not a replacement for water. If Class A foam is being used in a surround-and-drown defensive operation, the only smiling face may be the local foam salesman.

The use and integration of Class A foam into department operational procedures may be no small task. There are many considerations such as the foam agents, the method of application, equipment, tactics and safety considerations that must all be investigated. And after all the facts have been reviewed, the use of Class A foam, much like all firefighting, is still a very inexact science. What is known and proven every day is that the use of Class A foam as an enhancement to initial attack firefighting streams is a major benefit as we work both smarter and safer.

For additional information on operational considerations with foam, please contact the author and request the ‘Foam Operations Awareness Level’ PowerPoint/video.

  • Operation Florian

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