Fire departments that wish to implement the tactics used in this study will need to develop training and determine appropriate methods for deploying these tactics. Variations in the methods of deployment may be required due to differences in staffing, equipment, building stock, typical weather conditions, etc. There is uniformity however, in the physics behind the wind-driven fire condition and the principles of the tactics examined. These are discussed below.
Wind is a factor. As shown in these experiments, wind can significantly increase the thermal hazards of a fire within a structure. Wind conditions will vary at different elevations above the ground floor, on different sides of a building, due to the effects of surrounding structures or topography, or just changes in the wind itself. Therefore wind needs to be considered as part of the initial "size-up" of the fire conditions and should continue to be monitored and reported on throughout the fire incident.
Smoke is Fuel. A ventilation-limited (fuel rich) condition developed prior to the failure of the windows. Oxygen-depleted combustion products containing carbon dioxide, carbon monoxide, and unburned hydrocarbons filled the rooms of the structure. Once the window failed, the fresh air provided the oxygen needed to sustain the transition through flashover, which caused a significant increase in temperature.
Venting does not always equal cooling. In these experiments, the cool air that entered through the broken upwind window resulted in an initial period of cooling in the room of origin, typically followed by a transition to flashover, if a flow path was available.
Fire induced flows. Velocities within the structure exceeded 5 m/s (11 mph), as a result of the fire growth and the flow path that was created between the window opening and the open bulkhead door on the roof.
Avoid the flow path. The directional nature of the fire gas flow was demonstrated with thermal conditions that were significantly higher in the flow portion of the corridor as opposed to the position remote from the flow path. Thermal conditions in the flow path were often higher than 400 C (752 F) and inconsistent with firefighter survival.
Control the flow path. Wind-driven conditions with untenable thermal conditions cannot occur if there is no flow path through the structure. If the door to the stair on the fire floor is closed, the spread of fire and heat will be limited and wind-driven blowtorch conditions will not occur. In these experiments, after the fire room window failed, opening the fire floor stair door and the bulkhead door typically provided the flow path that led to wind-driven blowtorch conditions on the fire floor. Therefore, it is important to control and coordinate the opening and closing of doors within a structure. This study has also shown that WCDs, when deployed in a way to completely cover the window opening, were effective in mitigating the effects of the wind and controlling inlet of the flow path. The experiments demonstrated the importance of coordinating and controlling the opening and closing of doors which could provide a flow path, to avoid placing firefighters in the flow path. Firefighter training would be beneficial to identify and prepare areas which could be used as safe areas of refuge that are out of the flow path.
Use of PPV. Two 27-inch PPV fans could not overcome the effects of a wind-driven condition. However, when used in conjunction with door control, WCDs, and HRNs (tactics that stop the wind-driven condition), the PPV fans were able to maintain tenable and clear conditions in the stairwell. In each of these experiments, PPV use improved conditions in the stairwell.
Impact of WCDs. In these experiments, the WCDs reduced the temperatures in the corridor and the stairwell by more than 50 % within 120 seconds of deployment. The WCDs also completely mitigated any velocity caused by the external wind. The WCDs did not fail when they were exposed to a variety of extended thermal conditions. The WCD must cover the window opening completely to be effective. Pre-deployment of a WCD over the fire room upwind window prevented the development of wind-driven fire conditions. The benefit of using a WCD, compared to using the apartment door or the stairwell door, is that the flow path is interrupted at the entry point. This improves all of the conditions along the entire potential flow path.
Impact of externally applied water. In these experiments, the externally applied water streams were implemented in different ways: a fog stream inserted into the fire room window; a fog stream flowed from the floor below into the fire room window opening; and a solid water stream flowed from the floor below into the fire room window opening. In all cases, the water flows suppressed the fires, thereby causing temperature reductions of at least 50 % in the corridor and the stairwell. The water flow rates used in these experiments were between 125 gpm and 200 gpm, demonstrating that a relatively small amount of water directly applied to burning fuels can have a significant impact. Wind-driven fire conditions can generate and transfer energy throughout the flow path. When doors or WCDs are used to stop the wind-driven fire conditions, energy and fuel may be trapped on the fire floor. These experimental results indicate that the thermal conditions due to the residual heat on the fire floor, were still at a level that could pose a hazard to firefighters in full personal protective equipment (PPE). However, when used in conjunction with PPV fans to force cool air into the stairwell and out through the fire floor, and with the cooling effect from water streams, the fire floor temperatures decreased to tenable conditions for firefighters in full PPE within minutes.