With the support of the FEMA Assistance to Firefighters Grant Program, the UL Firefighter Safety Research Institute (UL FSRI) conducted 40 full-scale experiments in acquired structures of three different types. The goal of the Study of Coordinated Fire Attack in Acquired Structures project was to evaluate how tactical choices and coordination of ventilation and suppression affect conditions throughout structures where firefighters operate, to improve the safety and effectiveness of those men and women. Furthermore, occupant safety improves when firefighting effectiveness increases.
The specific objectives of the research included:
- Understand what coordinated ventilation and suppression is and how to best accomplish this mission.
- Continue to expand fire service research beyond the purpose-built, residential-scale structures that previously were studied to explore several occupancy types in acquired structures.
Three reports were created to document the experiments, the results and the considerations that can be used when assessing coordination on the fireground. Each report focused on a different acquired structure type:
- “Analysis of the Coordination of Suppression and Ventilation in Single-Family Homes.”
- “Analysis of the Coordination of Suppression and Ventilation in Multi-Family Dwellings.”
- “Exploratory Analysis of the Impact of Ventilation on Strip Mall Fires.”
Each report provides a fire dynamics analysis of all of the numerical data that were recorded during each experiment as well as tactical considerations for each set of experiments.
Single-family structures
Twenty experiments were conducted in eight acquired single-family homes that were slated for demolition; four homes were in Sidney, OH, and four homes were in Xenia, OH. To conduct these experiments, UL FSRI partnered with the Sidney Fire Department and the Beavercreek Township Fire Department.
Fourteen experiments examined second-floor bedroom fires; six experiments involved first-floor kitchen fires. Of the 14 bedroom fires, nine scenarios utilized interior suppression, and five employed initial exterior fire control that was followed by interior suppression. Of the six kitchen fires, firefighters utilized interior fire control on three; the other three were suppressed with exterior fire streams that was followed by interior extinguishment. Ventilation tactics included horizontal, vertical, positive pressure and hydraulic.
The experiments that sequenced ventilation before suppression revealed that fire growth and temperature increase in the fire room were possible even when initial ventilation and initial suppression were separated by no more than 30–60 seconds. In that time, ceiling temperatures in areas that were located between the fire and the low-pressure vent began to increase, while temperatures at lower elevations in the same areas decreased as fresh air was entrained. Water flow into the fire room resulted in a decrease in the heat release rate of the fire and, subsequently, lowered ceiling temperatures in areas that were remote from the fire room.
No meaningful increase in temperature outside of the fire room was observed for any of the ventilation tactics that were coordinated with (shortly before or after) the onset of suppression. After effective suppression, ventilation tactics should consider air flow that’s within the structure, with the aim of establishing air flow through all of the areas where occupants might be located. In general, the effectiveness of post-suppression ventilation varied, but the experiments in which toxic gas concentrations remained highest for the longest duration were those in which no timely ventilation actions were performed close to the occupant location.
Multifamily: garden apartments
Thirteen experiments were conducted in four vacant, 10-unit apartment buildings that had garden units, which were located in Marietta, GA. The buildings were provided by Cobb County and the Georgia Department of Transportation, and the experiments were supported by the Cobb County Fire and Emergency Services. Each building had the same layout: 10 apartment units that spanned three floors that were connected by an enclosed common stairwell. Two units were garden apartments, and there were four units on both the first and second floors. Each building was two stories on side A and three stories on side C.
For these experiments, the enclosed stairwell that was common to each group of 10 apartments was of particular interest. In 11 of the 13 experiments, the door from the fire apartment to the stairwell was closed prior to ignition. The two cases in which the apartment door was open prior to ignition had the highest toxic and thermal exposures at the measurement locations on each level.
For the 11 experiments that had the apartment door closed at ignition, the tenability of the stairwell was affected most when the suppression crew opened the door to make entry to the apartment. The use of door control, hydraulic ventilation, and positive pressure ventilation coordinated with entry and suppression lowered measured exposures. Both interior and initial exterior suppression tactics were effective at suppressing the fire and used similar amounts of water. The initial exterior suppression was effective at reducing the hazard at the apartment door for entry and, as a result, reduced the temperature and volume of gases that flowed into the stairwell following entry.
Strip malls
Experiments at a strip mall in Fairborn, OH, were supported by the Fairborn Fire Department. The building was a Type II-B construction that had unprotected, noncombustible structural elements. The load-bearing walls were masonry block; a corrugated metal, built-up roof was supported by open web, steel bar joists.
Seven experiments were conducted in four units to quantify the effect of horizontal and vertical ventilation on fire dynamics. In each scenario, the additional ventilation area (vertical or horizontal) increased the exhaust of combustion products and caused additional air to enter the unit. The air added oxygen to a ventilation-limited fire, and temperatures increased.
In the vertical ventilation experiments, flames were visible at the open vertical vents in the two experiments in which suppression was delayed. The flames weren’t an indication that all of the heat was being exhausted. In fact, flames were an indication that the heat that was within the structure increased and additional unburned fuels were being generated to burn outside of the structure.
Tactical considerations
For the duration of the project, the UL FSRI team collaborated with the Project Technical Panel (composed of 24 fire service representatives from around the country) to maximize the effect of each experiment for the purposes of improving firefighter safety and firefighter engagement with research.
Tactical considerations were developed based on results from the respective experiments through an iterative process with the technical panel for each of the three structure types. A tactical consideration is an evidence-based concept for the fire service to consider implementing to enhance efficiency and effectiveness and to increase knowledge to accomplish its mission. Unique tactical considerations were developed for each experimental series, but a common consideration across all of the experiments was the need to understand the timeline of coordination.
If ventilation is provided to a ventilation-limited fire (fire self-ventilates through window breakage, the front door is opened for access, or horizontal or vertical ventilation is conducted) and suppression is delayed, the ventilation increases the oxygen that’s available for combustion. When additional oxygen is provided to a ventilation-limited fire, the heat release rate of the fire increases. In the simplest sense then, minimizing the time between ventilation and suppression limits the amount of oxygen that could react with high-temperature fuel gases before suppression can cool gases and extinguish the fire. Therefore, it is important to be deliberate with fireground ventilation, particularly as it pertains to the timing of suppression.
Post-suppression ventilation should be strategically employed to facilitate tenable conditions.
Again and again
This research project’s experiments improved the understanding of the coordination of suppression and ventilation tactics. Although the types of structures differed and there was uniqueness to each set of experiments, a common theme is that coordinated ventilation and suppression—where crews on the fireground worked in concert to ensure minimal time lag between the initiation of the tactics—led to the best outcomes. Experiments with ventilation alone (i.e., without coordinated suppression) didn’t improve conditions for firefighters or the occupants who they protect.
For complete details on the experiments and resulting tactical considerations from the study, please refer to the reports, which can be downloaded from UL FSRI: Study of Coordinated Fire Attack Utilizing Acquired Structures.
