Coordination of suppression and ventilation in single-family homes
UL FSRI study details the effects of flow path control on victim survivability
This is the first article in a three-part series of articles about the UL Firefighter Safety Research Institute’s recent analysis of coordinated fire attack operations. Read Part 2 about the coordination of suppression and ventilation in strip malls and Part 3 about the coordination of suppression and ventilation in multi-family dwellings.
In mid-March, the UL Firefighter Safety Research Institute released the latest in a series of fire research studies concerning single-family dwelling fires – a 430-page report entitled “Analysis of the Coordination of Suppression and Ventilation in Single-Family Homes.”
This research was funded through the Assistance to Firefighters Grant (AFG) program, primarily to help with firefighter safety at our most prevalent and most deadly fire response: a structure fire in a single-family dwelling. The report is the first of three reports issued as part of the “Study of Coordinated Fire Attack Utilizing Acquired Structures” project.
The study utilized eight acquired structures in the Ohio communities of Sidney and Xenia, and included a total of 20 fire experiments – 14 fire scenarios in bedrooms and six in kitchen areas.
The experiments reviewed the effects on fire growth from various ventilation techniques; control of flow paths, such as from the door of entry; and both interior and exterior suppression techniques. The study also measured whether there was improvement in conditions for potential fire victims based on both suppression and ventilation tactics.
Fire growth basics
Before delving into the research, let do a refresher on the fire tetrahedron.
We know that in order to have a fire, we need oxygen, heat and fuel. To sustain that fire, we also need a fourth piece – a chemical chain reaction among these three basic elements. This UL FSRI study shows us, in part, how our suppression tactics affect the fuel and heat, while ventilation tactics affect the amount of oxygen that contributes to the fire.
Putting water on a fire reduces the temperature, cools the burning fuel and then wets or cools any additional surrounding fuel that would be needed to sustain the fire. Ventilation, whether horizontal, vertical, hydraulic or positive pressure, plus the control of the flow path, help limit the amount of oxygen that can reach the fire. As such, this study shows how the relationship between our suppression tactics and ventilation is critical in fire control.
The data analysis shows that the most efficient tactics occur following a 360-degree size-up, the first-arriving unit correctly assessing the status of the fire and, based on that assessment, taking one of the recommended tactics listed below.
The scenarios listed below were variations of coordinated suppression and ventilation tactics studied by UL FSRI. These scenarios are some examples of how to combat different types of fires in residential structures.
First-floor self-venting fire
If the first-floor fire has self-vented (e.g., fire or heavy black smoke and high heat coming from a window), crews could choose to use an exterior straight stream transitional attack directed at a steep angle to the ceiling of the fire room. After the fire darkens, the nozzle should then be closed to half-bale and an “O” pattern application can be used to help wet the contents.
This provides a cooling and wetting action, but using the same hoseline for entry may not be advised if it will take an extended period of time to reposition. That extra time might allow the fire to rekindle, plus the subsequent entry through an outside door may cause a flow path for the fire to again intensify.
If it would take more than a minute to reposition the hoseline for entry, the study suggests a second line might be deployed, if personnel are available, to begin entry and flow path control immediately after shut-down of the exterior hoseline. Once the fire is controlled, additional ventilation can be utilized.
Second-floor self-venting fire
For a self-venting fire on the second floor, crews could choose to employ an exterior straight stream transitional fire attack at a steep angle, hitting the center of the room’s ceiling, but due to the extensive time to reposition an outside line to the second floor, a second hoseline is recommended, again because the longer the delay (as little as one minute in a vented fire), the more time the fire has to again build to higher temperatures. Additional ventilation could be used after the fire is under control.
With fire showing above-ground level in a residential structure, I believe the initial fire company may want to extend a 2½-inch line with a gated wye, and deploy an initial 1¾-inch line, yet have access for a second line to be deployed by a second-arriving company.
In all of these test case studies, the approximate flow from the hoselines was 150 gpm. Total suppression and overhaul in all 20 scenarios took less than 500 gallons, but this is not a reason to change your first and second water criteria – but it does show the effectiveness of an initial transitional or “blitz” attack.
Effects of suppression and ventilation on potential victims
The UL FSRI study also reviewed the location of potential victims and the temperatures they face based on the tactics employed by fire crews.
Victims in the fire structure would see temperatures greatly reduced with any interior or exterior attack; however, it is only logical that the closer proximity of the victim to the fire, the less chance of their survivability.
With crews using the tactics detailed above, victims located between the point of entry, such as an entry door and the fire room, saw an immediate lowering of temperatures and carbon monoxide and carbon dioxide levels as well as an increase oxygen levels. Victims located beyond the fire room saw a decrease in temperature but not a corresponding decrease in any of these gas levels until additional ventilation took place.
One of the most critical takeaways is the coordination needed between suppression and ventilation, whether horizontal, vertical, or positive pressure. Maintaining control of the flow path, including the door of entry, is crucial to fire control.
Another key takeaway from these scenarios show that putting water on the fire significantly improves both fire conditions for the safety of firefighters and for the fate of a potential victim.
Finally, more than a one-minute delay between the shutting down of the exterior (transitional) application of water in a second-floor vented fire and initiating the interior attack allowed regrowth of the fire – hence the recommendation for two separate fire lines.
A fire dynamics tool
My advice to chiefs and training officers is to read the full UL FSRI study, analyze these test results in relation to your department’s current standard operating guidelines, and adjust your standard tactics as needed.
We are living in an age where fires grow hotter quicker, and the potential for flashover must be weighed at nearly every structure fire.
This study is another tool in helping us understand the dynamics of fire and offers us some new ideas and tactics on how to keep our firefighters and our citizens safer.
Editor’s Note: Have you found similar results in your real-life fireground experiences? Share in the comments below.