Smoke and heat spreading through the corridors and the stairs of a building during a fire can limit building occupants’ ability to escape and can limit firefighters’ ability to rescue them. Changes in the building’s ventilation or presence of an external wind can increase the energy release of the fire. This can also increase the spread of fire gases through the building.
Positive Pressure Ventilation (PPV) is being used by fire departments on smaller structures, such as single family homes, to control the fire flow by introducing pressure from the front door and venting the house through a strategic exit opening. If done correctly, this tactic can remove significant amounts of heat and smoke from the structure, thus improving the firefighters’ working environment and improving the chances of survival for the building occupants. However, it is questionable whether these PPV fans can be used successfully under wind driven fire conditions in large structures. Large structures, such as high rise buildings, provide additional challenges to firefighter and building occupant safety such as increased travel distance (exposure time), more complicated egress path, and potentially larger fires. Other tactics incorporating devices, such as fire window blankets or smoke curtains to control the ventilation conditions or the use of a special fire nozzle from the floor below the fire floor, have been tried by the fire service under “real fire” conditions with varying levels of success. Unfortunately, there has been no data to understand the capabilities and limitations of these firefighting approaches.
The U.S. Fire Administration and the National Institute of Standards and Technology (NIST), along with the Fire Protection Research Foundation, the Polytechnic Institute of New York University, the Fire Department of New York City, and the Chicago Fire Department, conducted this project to improve the safety of firefighters and building occupants by enabling a better understanding of wind driven fire fighting tactics, including structural ventilation and suppression. Further objectives included developing technical information that will enhance the understanding of the dynamics of fire phenomena and prediction of fire intensity and growth under wind driven conditions. Fire departments that wish to implement the tactics evaluated 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, and typical weather conditions. There is uniformity, however, in the physics behind the wind driven fire condition condition and the principles of the tactics examined. The data from this research will help provide the science to identify methods and promulgation of improved standard operating guidelines for the fire service to enhance firefighter safety, fire ground operations, and use of equipment.
Evaluating Firefighting Tactics under Wind Driven Fire Conditions (DVD set)
This instructional DVD set contains the two reports mentioned below and videos from all of the project’s experiments. It also includes a video presentation, wind driven fire condition During this dynamic presentation, Battalion Chief Jerry Tracy of the Fire Department of New York City, Battalion Chief Peter Van Dorpe of the Chicago Fire Department, Stephen Kerber and Dan Madryzkowski, both of NIST, provide an overview of the important wind driven research material.
Firefighting Tactics under Wind Driven Conditions: Laboratory Experiments
The first report, Fire Fighting Tactics under Wind Driven Conditions: Laboratory Experiments, documents the results from eight laboratory fire experiments that examined the impact of wind on fire spread through a multi-room structure and examined the capabilities of wind-control devices (WCD) and externally applied water to mitigate the hazard. The experiments were designed to expose a public corridor area to a wind driven, post-flashover apartment fire (the door from the apartment to the corridor was open for each of the experiments). The conditions in the corridor are of critical importance because that is the portion of the building that firefighters would use to approach the fire apartment or that occupants from an adjoining apartment would use to exit the building.
In summary, these experiments demonstrated the hazardous thermal conditions that can be generated by a “simple room and contents” fire and how these conditions can be extended along a flow path within a structure when a wind condition and an open vent are present. Two potential tactics, use of a WCD from the floor above the fire and external water application from the floor below the fire, were shown to be effective in reducing the thermal hazard in the corridor.
Firefighting Tactics under Wind Driven Fire Conditions: 7-Story Building Experiments
This second report, Fire Fighting Tactics under Wind Driven Fire Conditions: 7-Story Building Experiments, documents a series of 14 experiments that were conducted in a 7-story building to evaluate the ability of PPV fans, WCDs and external water application with floor below nozzles to mitigate the hazards of a wind driven fire in a structure. The results of the experiments provide a baseline for the hazards associated with a wind driven fire and the impact of pressure, ventilation and flow paths within a structure. During the experiments, wind created conditions that rapidly caused the environment in the structure to deteriorate by forcing fire gases through the apartment of origin and into the public corridor and stairwell. These conditions would be untenable for advancing firefighters. Each of the firefighting tactics evaluated during the experiments was able to reduce the thermal hazard created by the wind driven fire. In addition, multiple tactics used in conjunction with each other were very effective at improving conditions for firefighter operations and occupant egress.
From the USFA web site: http://www.usfa.fema.gov/fireservice/ops_tactics/firefighting/wind_driven/
Leave a Reply
You must be logged in to post a comment.