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Extrapolations: Beyond single family dwellings

As much is I appreciate the lifesaving contributions of fire dynamics researchers to the firefighting craft, I am continuously frustrated by the slow pace of the experimental process. Given that a limited number of projects, in particular the UL Ventilation and NIST/UL Governors Island tests (https://ulfirefightersafety.org/research-projects/vertical-ventilat...;), were able to demonstrate that decades of beliefs and practices were incorrect, which then lead to the development of effective alternative approaches that are also easier and safer, their value is indisputable. Because of these studies, we have been given back the use of external streams for immediate cooling, reminded of the dangers of uncoordinated ventilation, and freed from the imperative of cutting holes in the roofs of burning buildings. Unfortunately, since it takes virtually years to design, create, analyze, and report results, we won't be receiving additional contributions to our collective efficiency anytime soon.

A further limitation of this laboriously sluggish pipeline of innovation-inspiring information is that all of the full-scale, confirmatory experiments thus far performed were in single-family residential settings. Although it is true that one- and two-family residences account for the vast majority of structure fire incidents, deaths, and property loss in North America, there are plenty of other types of buildings that burn, and they are often bigger, more complex, and tougher to even enter than your typical home. While there have been some controlled, instrumented burns of large structures and high rises, these were usually merely observational, collecting data such as collapse time and smoke spread; or involved single interventions, such as creating or stopping ventilation. The single-family experiments, in particular the Study of the Impact of Fire Attack Utilizing Interior and Exterior Streams on Firefighter Safety and Occupant Survival (https://ulfirefightersafety.org/research-projects/impact-of-fire-at...;), have been both comprehensive, in that they included measurements of one or more firefighting actions (ventilation, structure entry, water application, etc.) and their effects on the entire burning environment, and also reproducible. Using the same structural configuration and contents in each trial allowed for the comparison and confirmation of results of different interventions and combinations thereof.

The prospects of performing similarly repeatable tests on larger and/or more complex structures is unlikely. (With a warehouse-sized building needed to house the single-family resident experiments, how large a structure would be needed to accommodate a commercial structure or garden apartment prop?) So, we're left with all of these new insights and tactics that haven't been formally evaluated regarding their application to settings other than single family residences. That said, although there are many good reasons for approaching fires in commercial, manufacturing, and multifamily residential settings differently, the physical properties that describe and dictate fire behavior are not necessarily altered. With some care and consideration, I believe we can extend the insights that have been proven in one situation to improve our performance in many others.

Note: Though it might go without saying, and could apply to anything I’ve written, the following (especially) is this writer’s opinion, as no confirmatory research exists, and probably never will, that could be cited as evidence. As usual, if you make the time, I’ll try to make my case.

I would like to propose two general rationales that support the application of some tactics proven only in single family residences to fires in other structures: 1) many features of fire dynamics are independent of setting, and 2) compartmentation can create a room-and-contents situation almost anywhere. In other words, the laws of physics always have jurisdiction, and small fires can occur in big buildings. Before you stop reading because it seems like I’m saying fires in factories and warehouses are the same as fires in a house, rest assured that I am not. Even with the exact same construction and fuel loads, fires in larger and more complex structures require different techniques that account for such things as delays in accomplishing forcible entry, longer hose stretches to the fire location, and unfamiliar layouts. And, the construction and fire loads are almost always vastly different than that found in residences. It’s just that the type of building in which the fire is located need not change everything about the fire or its extinguishment.

We now know that exterior streams, when properly applied (straight or solid stream, placed close to and aimed upwards into the opening in order to strike the ceiling, and with stream movement minimized [Straight, Steep, and Still - SSS]), will result in cooling in the burning compartment and communicating spaces, along with a contraction of gases that prevents the extension of products of combustion beyond the already-involved areas. Furthermore, we know that increasing the flow of air into a burning compartment results in an increase in heat production that is greater than that which can be released by passive ventilation, whether horizontal or vertical. These are based on principles of fire dynamics that have a solid scientific basis, and which were initially brought to our collective attention in explanations of firefighter line of duty deaths that occurred in circumstances that had overwhelmed firefighters who were following then-accepted tactics. The fact that we have not performed live-fire experiments in order to observe and measure these phenomena in larger buildings may render them only theoretical, but they are backed by stronger evidence than many of our other tactics.

Take the example of a fire that occurs on the first or second floor of a school, nursing home, office, or apartment building, with flames and smoke emanating from a window or doorway. Regardless of the building construction, contents, or number of potential victims, is there any reason that the initial use of an exterior stream should not be considered? Given the proven effectiveness of applying water from the exterior, the initial application of water should come from that direction if it can be accomplished most quickly. On the other hand, if there are exterior features (fencing, distance from paved surfaces, etc.) that limit access to the site of the fire, stretching through a doorway might be a better choice. The point is, exterior streams can make things better in any type of building fire, and should be employed when indicated.

On the flip side, if there were evidence of a fire that was not yet ventilated, in any type of structure, would there be justification for opening windows or the roof prior to the application of water? With the increase in burning intensity that follows the increase in air flow into a compartment fire, ventilation procedures, while vital, must necessarily await extinguishment efforts. Larger structures might offer a delay in ill effects from poorly-timed ventilation, if the fresh air being introduced needs to travel greater distance before reaching the seat of the fire, but any larger fuel load also has the potential to result in a correspondingly larger fire intensity. With these demonstrated effects, ventilation has become a tactic that should be performed only after extinguishment, instead of as the preliminary maneuver we utilized when it was thought to improve interior conditions for occupants and entering firefighters. Though no scientific observations have been performed that compare different tactical ventilation methods on larger structures, the principles remain consistent. (After all, you can use a doll house to demonstrate the effects of ventilation on a full-sized house.)

One type of structure that is amenable to a mixed approach, utilizing both traditional and modern firefighting tactics, is the multi-family dwelling. Even in high-rise structures, a fire localized to a single apartment can be managed in some ways like a free-standing single family residence, with ventilation to the unit limited by door control as the hoseline is stretched inside, while the common areas of the building (corridors and stairwells) can be ventilated early, preceding extinguishment, in order to facilitate evacuations. Of course, the construction, exposures, and other features of such an occupancy add substantial layers of concerns that must be addressed, but apartment fires behave in many ways like those in single-family dwellings.

Non-residential structures require different, and usually more, considerations and resources when involved with fire, and research that would confirm or prove the use of “modern” fire tactics has not yet been performed on those occupancies. Still, the “theoretical” methods of exterior water applications and delayed ventilation have a solid scientific foundation, independent of building configuration, and their application to more settings can be justified on the basis of both logic and common sense.

MJC

The author can be reached at markjcotter@comcast.net

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