As we continue to discuss and explore modern fire attack (MFA) methods, I thought it was time to start talking about what may be the greatest tactical change: we can stop routinely cutting holes in roofs and breaking windows of burning buildings! (And by "greatest" I mean the one offering the most benefits and challenges.) Now, you can read all of the recent fire dynamics research reports and analyses yourself and never find that recommendation, but I see it as a logical and practical progression of the structure fire fighting improvements already being implemented based on those experiments. I believe that eliminating, or even just reducing, the performance of vertical ventilation will significantly reduce risk, free up resources, and improve our efficiency on the fireground.
Here’s my reasoning: Live fire tests demonstrated that creating a ventilation opening above or beside a fire in a compartment increases the heat output of a fire, without improving conditions. The more ventilation, the hotter the fire becomes. Water application, on the other hand, has been shown to quickly and extensively cool the interior environment, even if initiated before entry (See MFA #4: The New Rules at http://community.fireengineering.com/profiles/blog/show?id=1219672%...). These findings lead to the recommendation that ventilation not be performed until after the burning fuel has been extinguished, so it will not react to increased air flow, and then only for the purpose of removing smoke and steam. Therefore, ventilation is no longer intended for fire control, but is an overhaul tactic, and should be considered as such when we make risk/benefit calculations regarding the best method for its accomplishment.
It was previously taught that ventilating a fire improved conditions for occupants and firefighters. In addition, it was emphasized that any fire that had “darkened down” due to having consumed the available oxygen within the structure - what we would now call “ventilation limited”, and which describes the stage of many fires upon our arrival - must be opened at the highest possible point in order release the pent-up products of combustion and prevent a backdraft explosion. With these motivations, it seemed reasonable to use whatever means necessary to quickly create openings in burning buildings, including destroying windows and damaging rooftops in the process. Immediately sending two or more firefighters above a fire and having them cut a h*** in the roof(s), and then the ceiling(s) below, at the time was thought to be an appropriate and necessary utilization of fireground resources (in this case, personnel, time, and luck). Based on the knowledge at the time, it was calculated that the harm inflicted to the building by this aspect of the firefighting process was justified by the harm prevented by more rapid fire control. Indeed, many of us have developed impressive skills in the performance of this difficult and hazardous process, and are rightly proud of those abilities.
With recent live-fire experiments instead demonstrating the necessity of limiting, to the extent possible, the amount of air flow to a fire involving today's contents, the previous ventilation mandate has been repealed, and we must re-evaluate our approach. No longer is there an urgent reason to commit personnel to the time-consuming, dangerous, and, as we now know, unproductive process of opening rooftops, or even the extensive removal of windows. Certainly the increase in visibility and decrease in temperature that result from post-extinguishment ventilation are beneficial, but with the fire at that point already controlled, we no longer have the justification of causing damage to prevent damage. Many of us veteran firefighters have found it necessary at times to step in to prevent over-eager rookies from breaking windows long after a fire is extinguished, and this new insight should inspire the entire fire service to undertake a similar reconsideration of what have become our routine actions.
My personal misgivings about vertical ventilation are a recent development, arrived at only after repeated exposure, over several years, to the findings of the fire dynamics research that consistently contradicted any claims of its benefit. In fact, I fought hard, for many years, to increase the use of ventilation. For some departments with whom I served, a h*** in the roof was usually there only because a fire had burned through, and we struggled to improve our ability to perform vertical ventilation in a more timely manner. Training, equipment improvements (specifically, motorized cutting tools), SOPs, critiques, and more training eventually brought us to the point of integrating this step into our fire suppression efforts, though we were often holding back on entry and water application as we focused on that tactic. Now I work with firefighters who can vent a roof almost as quickly as we can stretch hoselines, and our challenge is to restrain them until water flow begins. For example, I was once on the first-in Engine with my current Department at a 3rd floor garden apartment fire when, as we searched the unit, the smoke cleared and a shaft of light from the ceiling – or, at least, from where the ceiling had been before the truck crew cut a vent h*** in it - illuminated the site of where a small fire had self-extinguished. And we on the Engine had arrived on-scene first!
Considerations about which method to utilize for smoke removal need to include firefighter safety, ease and speed of performance, collateral damage, and effectiveness. Vertical ventilation is, in fact, the most efficient natural method, but only in the narrow context of comparing the passive movement of smoke between either vertical or horizontal openings. In other words, if you have ready-to-open exhaust paths to the side of or above a fire, as the live fire experiments had built into the structures they were using, the rooftop route removes the products of combustion better. But, while hot gases will self-exhaust upward more quickly than laterally, and will do so even without the assistance of fans or hose streams, actually creating an opening in a roof and ceiling(s) of sufficient size to allow for this natural movement, in the best location, and in a timely manner is, as we all know, no easy task, and not without significant drawbacks. Furthermore, with a charged hoseline already in hand, and likely a portable fan on the rig, why should we limit ourselves to natural ventilation when we can augment and direct the exhaust of products of combustion? Certainly, any existing rooftop openings that allow the passage of smoke (e.g., bulkhead doors, hinged skylights) should be utilized, but, lacking the presence of such vents, I would argue that the risk, effort, time, and destruction entailed in performing vertical ventilation renders it far from the most efficient method.
Obviously, getting to and operating upon any roof is dangerous, designed as they are for shedding the elements rather than supporting groups of heavily-equipped and vigorously working firefighters. Such factors as pitch, darkness, smoke, and precipitation, frozen or otherwise, commonly add to the hazards, while fire burning below multiplies them. Once the roof is successfully mounted and footing is secured, actually penetrating the multiple layers of roofing material, and avoiding structural (supporting) members, all the while coordinating theses actions so that they are completed immediately after the application of water, requires yet another feat of skill, daring, and, sorry to say, luck (that there was not a rain roof, collapse, miscommunication, or any other mishap).
The preventable damage issue is significant. A friend who makes his living as a remediation contractor, making repairs necessitated by fires and firefighting, informed me about the downstream costs associated with our line of work. Boarding up a broken window at about $50.00, or a roof vent at $100.00, is just the beginning. When damaged, modern windows need to be replaced in their entirety, with a unit cost in the $200.00 to $300.00 range, and installation easily doubling that price, accompanied as it often is by the need to replace/repair trim, siding, etc. On the roof, closing the h*** we make is relatively straightforward, especially if we keep to our textbook 4-foot by 8-foot size, unless rafters or, God forbid, trusses are also cut, necessitating their repair. The real money is typically spent to replace the shingles on the entire surrounding slope, or “field”, if not the whole roof, in order to restore a uniform appearance. This can easily run into several thousands of dollars. All of these costs, of course, assume we were successful in checking the fire damage before it rendered the structure unsalvageable, a condition reached quite rapidly in many cases.
The alternative approach to ventilation after fire control is to choose an exhaust opening, which the fire has often already done by causing a nearby window to fail, or by opening a window if all remain intact, and then directing a water stream out of the window to pull, or placing a fan at the entry to the fire area to push, the smoke out. In this manner, the products of combustion are removed from the structure in a rapid and controlled manner, and via a more efficient and safe utilization of personnel. (The subject of Positive Pressure Ventilation [PPV] will be the topic of a future MFA post, but keep in mind this point: if conditions worsen after ventilation is performed, a fan can be turned off, but a cut roof cannot be closed.)
Our newfound knowledge of fire behavior has allowed us to revise our approach, in the process making firefighting a little safer, easier, and faster, though it remains, admittedly, far from safe, easy, or fast.
PS: I appreciate the support and interest from the hundreds who have been following this series on Modern Fire Attack, and would encourage anyone who notices anything I may have left out or misinterpreted to utilize the handy Comment box that follows this post to add their voice to this discussion.
Thanks for the encouragement and compliments, and, I have to admit, it's hard for me to disagree with someone who says he agrees with me so much, but here goes:
I maintain my position that the importance of vertical ventilation as it relates to a working structure fire is in avoiding its use. While I am not recommending it be removed from our playbook, any more than other tactics like attacking from the unburned side or searching without a hoseline that have had their efficacy questioned, my point was to have us all take a collective step back from what has become almost a reflexive maneuver, the usefulness of which has been effectively disproven.
This holds true also for attic fires, which my article did not address specifically, but which have been covered quite nicely in an Underwriters Laboratory (UL) training program available online here:
Addressing ventilation specifically, the UL findings lead to this recommendation: "Closely time or limit vertical ventilation until water is in the attic. In the absence of suppression, the positive effect of a roof opening is a very short lived phenomena. Increased visibility does not automatically mean a reduction in the size of the fire over your head. The accelerating fire will quickly overwhelm all openings and push back into the occupied space." In other words, ventilation makes attic fires worse, just like it does for fires in other parts of structures.
Regarding improvements in victim survivability, search efficacy, or flow paths (above rather than behind), ventilation before suppression has been shown to provide just the opposite. I therefore have no concern regarding keeping firefighters off the roof as I can find plenty of actually productive things for them to do (search, backup hoselines, relief, etc.). Finally, while I do not have the answer as to the relative numbers of firefighters killed by flashover vs. while performing ventilation, we now know that ventilation doesn't prevent flashover, and any firefighter killed or injured performing a unnecessary tactic is one too many (and I personally know of several).
To return to my original point, once the fire is controlled (cooled, extinguished, knocked down, whatever), is cutting a h*** in a roof, with all of its attendant difficulties and dangers, at all necessary? If not, is vertical ventilation really a "good play", or merely an old habit?
I really want to thank you for taking the time to read and respond to my arguments, and I encourage you to do so again if you see my logic in any way as unreasonable or poorly explained. I know how difficult it is to integrate the fire dynamics research finding into our fire suppression routine as I had to do so myself, and it required an almost wholesale reconsideration and reprioritization of an understanding of fire suppression tactics and strategy that I had been developing over decades. This Modern Fire Attack series is an effort to share and discuss the many "reversals of opinion" involved in that un-learning process.
What a great topic to discuss. Thank you Mark for laying the foundation towards a more educated fire service. Much of your article is spot on as it relates to the science of fire. As we continue down the road towards a science driven fire service, we are beginning to loose sight of what the fire is trying to tell us. An article such as yours highlights some key points to understand while engaged in suppression, what I believe it is lacking is the tactical application to our duties. I'm reminded of the first few years of my career when I would ask my Captain or other supervisors about specific fireground duties ("how would I pull this line and to where", "what will the fire do if I do this" ect.) the answer I all to often got was "its dynamic" or one of the worst phrases in the fire service "its situational" (these are a close second to the worst phrase "the fire went out and everyone went home"). These comments always ate at me and showed a lack of looking deeper into a situation and it approached everything as if it were the same.
I would like to reiterate the importance of vertical ventilation as it relates to the working structure fire. As we look at the differing fires we are faced we must keep this in our playbook.
While working at attic fires we must keep vertical vent as a tactical priority especially for a "ventilation limited" fire. Your first approach is to go inside, pull ceiling and find the fire... Not necessarily the case if you find thick smoke and no fire, at this point you would continue throughout the home pulling ceiling and praying you find it. With a COORDINATED crew on the roof they can pop a whole, get the lift you need and show exactly where your fire is at. We have now reduced the time it takes to begin adequate fire attack and create a safer environment for the brothers on top and those below. We have also stopped the lateral spread of the fire (running towards the gables looking for O2) and limited the roof members that will be burned through. As for restoration, everything from the top of the walls up will be replaced, regardless of the vent h*** when dealing with most attic fires.
The article did not discuss anything about occupants trapped or how thick smoke may hinder a primary search and subsequent survivability of the occupants. Bouncing off furniture while conducting a search has always been much easier, quicker and safer once the vent group has completed their job.
The science today is also telling us so many things about flow paths. Ill take a "flow path" high above me than the one behind me as we came through the door (especially on a vent limited fire). For future articles I would like to see how the science you are writing about relates to studies provided from the flow path findings.
My last point of concern is not getting people on the roof. Our vent groups of today are not up there to watch the birds, they should be providing adequate CAN reports from the roof while keeping a constant eye on the structural integrity of the roof. If something goes wrong inside, they are there to start opening holes to give our guys inside a chance. I agree with you, we should not be opening up holes just for the sake of some table talk later in the shift. However, when confronted with the borderline fire (to cut or not) there is no better training environment for all members on the roof than that. Our younger guys begin to develop a fireground confidence in their abilities as do there supervisors. If the fire extended into any part of the attic, its should be game on for the guy holding the saw. And contrary to the article, we can cut a h*** and maintain the seated position of the louver. This will now give us the h*** "on-demand".
All of this information has provided us with a great foundation for "the modern fire service". I want to personally thank you for the time you took to study the information and share it will those willing to listen. And yes I am listening, this is not an article bashing as I fully agree with most of the science you presented. I cannot sit on the sidelines however when I see good plays being removed from the game plan. As we continue to push forward, I hope future research is done in a real life manner. One where you may not know the exact location and extent of the fire. These intangibles are some of the things that lead to the NIOSH top 5. These are the times when you need a h*** to locate, confine and extinguish.
In closing, I would encourage every firefighter to read the statistics on how many firefighters are actually killed while engaged in Ventilation Operations. It won't take long to research as there is not many. Then research the amount of FF's killed in flashovers or other forms of dynamic fire behavior due to a lack of ventilation. Once you are informed, we can elaborate on this discussion.
Final thought is anything done on the roof should be done in a COORDINATED manner with the interior crews.
Thanks again Mark! Stay safe and stay engaged.
"An ounce of action if worth a ton of theory"
Thanks for your thoughtful and learned comments, and for offering me the opportunity to further explain my position. You are correct in your summary of the research findings, and I admit that I overstepped the recommendations of the UL and NIST studies, but I stand by my statement that, all things considered (time, effort, risk, damage), vertical ventilation is probably the least efficient method available for "cooling, increased visibility, useful flow paths opposite a hose line to release steam and other benefits." While I may be wrong, I decline the label of "myopic", as I was actually considering the process of vertical ventilation in its entirety, rather than, as in the UL and NIST research, it compared the effects of opening a pre-built rooftop trap door. Also, I used the word "extinguished" because I failed to come up with a word that conveyed cooling a fire to the point that it would not respond to increased ventilation. Probably "knockdown" is a better term, but the difference between the two is that of a few seconds of water application to the burning material, the action required in order to achieve the fuel-limited state.
Regarding the Governors Island experiment that opened the vertical vent, then closed the front door, and found a decrease in temperature in most areas of the apartment, my thoughts are that this confirms the principle that air flow is bad for fire control (though good for removal of smoke and steam after fire control). Other experiments also consistently showed that limiting air flow to a fire decreased its temperature, although not as much as applying water.
Again, my point is that, having worked hard to knock down a fire without ventilation, why go through the bother of cutting a h*** in a perfectly good roof when the benefits of ventilation at that point can be achieved by much easier, safer, and more efficient methods?
Finally, I have no idea why the FE Community turns the word h-o-l-e in to h***, but it's not my doing.
Mark, I appreciate you writing this and putting yourself out there, but I have to state that I think that your view of vertical ventilation and the research done by UL and NIST is a bit myopic. UL's Vertical Ventilation Study reinforced our understanding that in vent-limited, contents fires with an open front door, going topside and creating a vent h*** will increase the air entraining through the front door and thusly increase the heat release rate of the fire (see Law of Conservation of Mass, Thorton's Rule, fire triangle, etc.). This should not be knew to any of us.
I believe that you are reaching when you stated UL recommended "that ventilation not be performed until after the burning fuel has been EXTINGUISHED, so it will not react to increased air flow, and then only for the purpose of removing smoke and steam." In fact, UL states, "As soon as water has the upper hand, and more energy is being absorbed by the water than is being created by the fire, then ventilation will begin to work as intended." - this is not talking about extinguishment, but rather the beginning of knockdown. UL also goes on to state that "Venting does not equal cooling; well timed and placed ventilation equals improved conditions. These improved conditions are: cooling, increased visibility, useful flow paths opposite a hose line to release steam expansion and other benefits."
Also, there's an interesting experiment from UL/NIST's Governor's Island Study where after the front door was shut (after a vertical ventilation h*** was created), most areas of the apartment decreased in temperature. I'm curious about your thoughts on this experiment?
© 2023 Created by fireeng. Powered by
You need to be a member of Fire Engineering Training Community to add comments!
Join Fire Engineering Training Community