Fire Engineering Training Community

Where firefighters come to talk training

Water Rules: Summary of the recent UL Studies Part 4: Full Scale Experiments - Tactical Recommendations

Concluding my series of commentaries on the findings of the “Impact of Fire Attack Utilizing Interior and Exterior Streams on Firefighter Safety and Occupant Survival” collection of UL experiments, this installment will cover the 18 "Tactical Recommendations" from the "Full Scale Experiments" ( Inspired by the findings from this study, but also referencing those of several prior UL research projects, including the Water Mapping and Air Entrainment portions of this series of experiments, and other fire attack and ventilation tests performed over the past decade, these "lessons" were compiled by the members of its Fire Service Technical Panel:

Name                          Fire Department

Steve Brisebois           Montreal Fire Department

Matt Carrigan              Montgomery County Fire and Rescue Service

Tony Carroll                 District of Columbia Fire and Emergency Medical Service Department

Albert Castillo              Houston Fire Department

Chad Christensen       Los Angeles County Fire Department

John Chubb                Dublin Fire Brigade

Danny Doyle               Pittsburgh Fire Department

Aaron Fields               Seattle Fire Department

Jason Floyd                Las Cruces Fire Department

John Gallagher           Boston Fire Department

Chad Green                Anchorage Fire Department

Kelly Hanink                Riverside Fire District

Samuel Hittle              Wichita Fire Department

Jacob Hoffman           Toledo Fire/Rescue Department

Josh Hummel             Howard County Department of Fire and Rescue Services

Jerry Knapp               West Haverstraw Fire Department

Dennis Legear           Oakland Fire Department (Ret.) / LEFD Consulting

Nick Martin                Columbia Fire Department

Ray McCormack        Fire Department of New York

John McDonough      New South Wales Fire Department

Jordan Mohr              Sedgwick County Fire District 1

Hans Neiling             Zuid Limburg Fire

Steve Pegram           Goshen Township Fire and EMS

As with my previous installments, the reader is encouraged to review the study itself, rather than relying on this writer's opinions and interpretations. If for no other reason, the amount of valuable information in the report far exceeds that which can reasonably be included in this format, so making the effort to study the details is time well spent. I have also condensed the 18 separate recommendations into three related groups, covering what I believe to be the most important finding (Fastest Water Wins), data on survivability (Extinguishment Supports Rescue), and assorted new insights (Practical Lessons). (Please note that this approach will result in a list that is in a slightly different order than that which is included in the original document.) The numbers preceding each topic refer to the corresponding section of the report, where additional supportive and explanatory information can be found.

Fastest Water Wins
Four of the recommendations serve to describe this key takeaway from the experiments, each addressing it from different perspectives, with 7.7 Water in the Fire Compartment Matters, and so does Timing doing so most clearly. This advice emphasizes that it is not important from which direction (exterior or interior of the structure) the water is flowed, but how quickly it can be placed into the room containing the burning material. The previous arguments about attacking from the unburned or burning side have been muted by the new understanding that the best choice is whichever side you can reach first with the hose stream. 7.2 Transitional Attack With Fire Showing Near the Entry Point and 7.3 Fire Showing Remote from Primary Entry Point cover the two general situations a nozzle operator will face, each still concluding that the best choice is that which will most quickly allow water to reach the burning material.

Finally, 7.1 Interior Suppression With Only Smoke Showing addresses the circumstance where the seat of the fire is not immediately evident, as when an entire structure is charged with thick smoke, and suggests that in that instance an immediate attack from the nearest entryway should be initiated. While this advice is pragmatic and sound, it is only applicable when there is a failure of the various methods of determining the location of the fire, particularly the 360 degree survey and the use of a Thermal Imaging Camera (TIC). Also, this “When in Doubt, Go In and Put it Out” approach is easier to apply to the "laboratory" setting the expert panel was considering, where the location of the fire was known to be on the entry level, there was no basement, and attack was initiated before the structure had time to decay. At any non-staged incident, the presence of extensive smoke and heat exhausting under pressure requires careful analysis before committing interior crews. Still, the underlying message - that getting water onto the fire is the primary goal, from whichever, or any, direction - remains valid.

Extinguishment Supports Rescue
Our number one priority remains Life Safety, and it is considered second in this discussion only because Fire Control, or, more specifically, Water Application, was the focus of this study. Still, lingering concerns about the effects of hose streams on victims have dominated recent discussions amongst firefighters more than the effects of hose streams on fires, so this was a vital component of the overall analysis. For those of us who have supported the Principles of Modern Fire Attack, the results confirmed our position. 7.5 Fire Attack and Search & Rescue Can Occur Simultaneously removes the either/or dichotomy amongst fire tactic theorists. That is, we don’t need to delay or otherwise limit extinguishment efforts while we search. Now, staffing realities may certainly constrain our choices, as you cannot do both simultaneously unless you have sufficient personnel; and proper nozzle technique is required to prevent deterioration of the interior conditions that might affect searching crews, much less trapped civilians. Still, I maintain that extinguishment is often quicker, easier, and more effective in protecting occupants than searching an entire structure, and will typically also improve the efficiency (speed and effectiveness) of the latter process. This new information further supports this opinion.

The primary finding leading to this conclusion is 7.10 Suppression Operations Did Not Increase Potential Burn Injuries to Occupants. Despite the understandable hesitation firefighters have harbored about the potential for ill effects from steam creation and heat spread resulting from hose streams, the various instruments arrayed within the structure to analyze such data as temperature, water concentration, smoke movement, and tissue damage found no evidence of deterioration in conditions after extinguishment was initiated. It is also important to note that this recommendation is not endorsing one suppression approach over another, as neither exterior nor interior attacks showed an increase in the factors that would cause burns. In yet another example of the researchers’ thoroughness, though, they actually tested the only other alternative, which would be to allow the fire to continue to burn. They ran a “no intervention” scenario for each of their three fire types [No vent, One Room/One Vent, and Two Room/Two Vent] that demonstrated the consistent danger of any delay in initiating water application.

Practical Lessons
This final, “miscellaneous” category of recommendations should not be construed as containing topics of any less importance than those that support the first two. Some of them are new concepts, while others are confirmations of previous findings, but each represent a vital principle about which all firefighters must be knowledgeable in order to best accomplish our mission.

7.4 There Can Be Survivable Spaces on Arrival at a Single Family Residential Home and 7.6 Search Consideration: Closed Doors Significantly Increase Occupant Survivability emphasize the factors that protect occupants from death in fires, specifically being lower than the smoke layer, and separated from the fire by distance (good) or compartmentation (better). A closed bedroom door was reaffirmed as a surprisingly effective and durable barrier to heat and toxic gases. Depending upon staffing and other circumstances, the best method for actually saving occupants in the survivable spaces may be by removing them or by extinguishing the fire. It was emphasized, though, that entering a closed room via an interior door to perform a search before fire control, and thereby introducing into that space the very elements from which we are attempting to protect victims, should be avoided.

7.8 If You Can Get Water to Where it Needs to Go, You Don’t Need Much is based on the finding that it took only about 30 gallons of water flowed into each of the burning rooms to effect knockdown, albeit with additional flow required during interior attack to cool during the advance of the nuzzle, and in every case afterwards to complete extinguishment and perform overhaul. No one, of course, is suggesting we should carry less water on our apparatus or curtail laying supply lines, especially since the fires analyzed involved at most two rooms in a single story dwelling. What this does demonstrate is the surprising effectiveness of water for controlling ventilation limited fires, which describe most of the structure fires we firefighters will face. (This is also not a new concept, as it formed the basis of the Iowa Fire Flow Formula that was developed by Keith Royer and William Nelson in the 1950s [], which remains accurate even with our "modern", petroleum-based contents and their higher heat output when burned.)

7.9 Water Flow Can Impact Flow Path might appear to be an affirmation of the previously-taught notion that exterior hose streams can "push fire", a concept that was somewhat incompletely dismissed after earlier research with the statement that "You can't push fire with hose streams". The practical reality is somewhere in the middle. While you certainly cannot push flames with water, any more than you can push a balloon with a needle, you definitely can push heat and smoke, which is probably just as bad, by the use of certain nozzle techniques. Also, since those products of incomplete combustion can be transitioned to flame once they reach an oxygen source, propelling them out a window, door, or other exhaust site can result in a rather dramatic ball of fire being “pushed” outward.

These experiments confirmed that our water application methods have predictable effects, and, when performed correctly - that is, the right technique for the situation at hand - we can use them to our advantage. During interior attacks, flowing water down the corridor towards the seat of the fire pushed products of combustion away form the nozzle team, especially if there were a flow path established (i.e., open window[s] in the burning compartment ahead of the hose team, and open entry door behind), but even when there was not. On the flip side, for exterior attacks, the use of straight or solid stream to minimize entrained air, angling it steeply upward in order to strike the ceiling as near to the front wall as possible and maximize the distribution of water spray, and keeping the nozzle still in order to minimize blockage of the release of products of combustion (“Straight. Steep, and Still” - SSS), resulted in no movement of products of combustion deeper into the structure, even in the presence of an exhaust (open window or door) beyond. Wider exterior streams for further wetting down burning contents after initial knockdown were used only when the nozzle could be placed into the room and thereby not entrain air. So, you can use hose streams to push smoke and heat when it might help, and can avoid it when it might harm.

7.11 Speed of Transition is the Enemy of Re-Growth is a “bumper sticker” phrase that highlights that fire knockdown provides only initial, and temporary, cooling, and getting a hoseline into the burning compartment to complete extinguishment remains necessary. Still, exterior water flow resulted in cooling that persisted for at least the 40 seconds it typically took for the crew to stretch the same hoseline indoors and reach the fire room. This component of the attack might also be considered as an extension of the series of decisions that attempts to address the Fastest Water Wins goal, completing, as it does, the process of extinguishment.

7.12 Water Converted to Steam Expands, Hot Gases Cooled Rapidly Contract is the science lesson that explains much of the contrarian fire behavior that has been observed in this and previous fire dynamics experiments, in that the second reaction is greater than the first. While the fact that the volume of water increases by a factor of 1,700 when it is converted to steam is well-known extinguishment trivia amongst firefighters, conveying as it does an appreciation of the immensity of that reaction, the simultaneous, opposite, and more profound effects of cooling had previously been almost equally unappreciated. (For this writer, the findings at the Governors Island experiments that water application consistently resulted in universal cooling, even in areas adjacent, or even just an open stairway above, the fire compartments, where I had been sure a cloud of steam should have billowed, first demonstrated this phenomena with sufficient clarity to finally switch on the light of understanding in my thick head.) Understanding and acknowledging this reality are necessary steps for maximizing our extinguishment skills.

7.13 Water Vapor is a Bi-Product of Combustion is another concept that, while not actually debunking our previous fears about steam production from water application, instead helps put it to rest by putting it into perspective. Representing one of the more challenging data collection endeavors for researchers, with the quantity of water in smoke being technically difficult to measure, the results were well worth the effort. It is important to remember that steam is invisible, a natural byproduct of the process of combustion, and but one of many gases that make up the toxic and often combustible mix that we call "smoke". The measurements were taken at an uninvolved room with an open door and a closed window, representing one of the very types of locations we had been concerned that steam would travel to affect occupants.

What was found was that the concentration of water in smoke, aka "steam", increased steadily as the fire progressed, but, at the 1-foot level, little or none after the application of water for extinguishment. This suggests that a victim on the floor, out of the flow path, would be unaffected by steam created by extinguishment efforts. At the 3- and 5-foot elevations, the concentration of water vapor in the smoke did increase after water was introduced into the burning compartment, but at a rate similar to that which had occurred from the time of ignition to before water application, suggesting that the increase may have occurred even if the process of combustion had not been curtailed. Combined with 7.10 and 7.12 above, this data represent additional nails in the coffin of the "steam monster" we have been taught to fear these many years. (Of course, the only guaranteed method of preventing the creation of more steam is to utilize something other than water as an extinguishment agent.)

7.14 Flow vs. Shutdown is a debate I had been unaware of prior to reading this report. Continuously flowing water as the hoseline is advanced indoors, termed “Flow and Move” (F&M), a technique I had practiced only for outdoor flammable liquid or gas fires, and then using only fog patterns, has been promoted for its ability to propel products of combustion back towards the fire, and away from the nozzle crew, even when flowing a straight/solid pattern. When compared to the practice of merely flowing water, closing the nozzle, advancing the line, and then resuming flow, termed “Shutdown and Move” (S&M), F&M was shown to achieve more consistent flows of heat and hot gases back down the hall to the fire compartment, even in the absence of an open window. When performing S&M, gas flow ahead of the hose team would cease and overhead heat would increase while the nozzle was repositioned. Still, the practical benefits of one method over the other were not shown, as even a brief flow of water moved products of combustion significantly, and the intermittent rises in temperature in just the upper levels of the hallway between periods of water flow were not sufficient to affect a hose crew making a push while crouched down. Also, the limited duration of the S&M water flow was somewhat compensated for by its accuracy, as a stationary operator was found to be better able to aim the stream and maximize its effects.

7.15 You Should Cool as You Advance is another MFA slogan reinforced by this study’s findings, as temperatures in these fully-developed blazes would have likely prevented interior crews from advancing near enough to the fire compartment to reach it with a hose stream without first flowing water into the overhead gases. The lack of ill effects from interior water application, as discussed above in Extinguishment Supports Rescue, render it not only helpful, but harmless. Put another way, why would we not wish to begin improving interior conditions as soon as possible by flowing water as we stretch through a smoke- and heat-charged structure?

7.16 Understanding the Limitations of a Thermal Imaging Camera can be summarized as not relying on those devices to measure temperatures, because accuracy decreases as fires progress to fully-developed/flashover stages. So, use them to find heat, not measure it.

7.17 A Short Burst Cannot Tell You Gas Temperature actually debunks advice I had been dispensing regarding gas cooling, as water sprayed overhead and then splashing back down was thought (by me and others) to indicate the absence of elevated temperatures. The researchers instead repeatedly found that directing a straight/solid stream even into hot, ready-to-burn-if-more-oxygen-were-present gases would allow some water to return to the floor without vaporization. With this maneuver now discredited, and our Thermal Imaging Cameras unreliable for that purpose, the reader is referred again to 7.15 You Should Cool as You Advance.

7.18 Large Volume Gas Cooling Requires a Large Volume of Water summarizes a separate experiment performed in one of the same structures used for the other demonstrations, but with most of the interior walls removed. The fire was set in one corner of the structure, behind the sole remaining wall, the intent being to create a large amount of overhead, heated smoke in order to measure the effects of various water application methods on temperatures. What was found was that spraying water overhead, in a space that approximated the interior of a burning garage or small commercial facility, resulted in only minimal, brief reductions in temperatures, with the most significant and prolonged improvements occurring after higher and longer flows.

This study measured the effects of attacks on fires in single family residences from the interior, exterior, and combinations thereof. The intent was not necessarily to compare their relative effectiveness, but to provide new insights and understanding that we can apply to the infinite variety of circumstances that surround the processes of combustion that we will be summoned to control. A key lesson is that there is no practical difference in the resulting environment within a burning building when water is flowed from the exterior vs. the interior, so we can put to rest many of our previous concerns and assumptions regarding the ideal direction of fire attack, and instead focus on how to most quickly begin to apply water into the burning compartment.

While the results of these detailed and comprehensive experiments might be accurately summarized with the simple formula: “Fire + Water = Better”, the process of structure firefighting remains complex in both understanding and performance. Achieving mastery of our craft requires that we assimilate this new information into our teaching and practice, an undertaking that will look different and require a unique level of effort for everyone reading this blog. Still, it is new knowledge such as this that drives the advancement of our individual and collective skills and abilities.

Keep in mind that the outcomes of these experiments have not so much told us what we should do, but what happens when we do it, allowing us to determine how to best apply these new insights.


The author can be reached at

Views: 994


You need to be a member of Fire Engineering Training Community to add comments!

Join Fire Engineering Training Community

Policy Page


The login above DOES NOT provide access to Fire Engineering magazine archives. Please go here for our archives.


Our contributors' posts are not vetted by the Fire Engineering technical board, and reflect the views and opinions of the individual authors. Anyone is welcome to participate.

For vetted content, please go to

Fire Engineering Editor in Chief Bobby Halton
We are excited to have you participate in our discussions and interactive forums. Before you begin posting, please take a moment to read our policy page. -- Bobby Halton

Be Alert for Spam
We actively monitor the community for spam, however some does slip through. Please use common sense and caution when clicking links. If you suspect you've been hit by spam, e-mail

FE Podcasts

Check out the most recent episode and schedule of

© 2022   Created by fireeng.   Powered by

Badges  |  Report an Issue  |  Terms of Service