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The Dangers of Wind-Driven Residential Fires

Somewhere in the country, a crew of firefighters will initiate a fast and aggressive interior attack at a residential structure fire only to be engulfed in a rapidly advancing and blinding wall of fire. As a result, the crew will instantly become disoriented and some will not be able to evacuate the structure.

Risk management often used by firefighters during interior structural firefighting operations involves the act of avoiding the anticipated danger within the structure. Another method to manage risk on the fireground consists of using a "risk-benefit analysis." Conversely, a risk-benefit analysis makes the assumption that the risk is known. However, a safety problem identified concerns the fact that in several fatal wind-driven fire cases examined, firefighters either overlooked or were totally unaware of the extreme danger associated with the wind speed and direction in relation to the position of the fire.

The oversight of this key fireground factor during the initial size-up was a contributing factor that ultimately and unfortunately lead to unfavorable outcomes. With appropriate planning, training, and tactical adjustments however, extremely dangerous wind-driven fires can be recognized so that firefighter fatalities may be prevented.

Case Study

As 12 to 15 mph winds gusted up to 24 mph, pressurized a vented fire on the Charlie side, San Antonio, TX, firefighters were engulfed by a rapidly spreading, wind-driven wall of fire after advancing an 1 3/4-inch handline through the front door at this two-story residence (see Photos 1 through 4.) Although firefighters were temporarily disoriented by the fire, they all made a narrow escape.

Occupants managed to safely exit the structure prior to the firefighter's arrival (see Photo 1.) A 360-degree walk-around revealed fire venting out of the first floor windows on the Charlie side (see Photo 2.) During the incident, fire quickly spread from the first floor on the Charlie side, up to the second floor and into and across the attic space. The wind-driven fire then burned through the roof on the Alpha side of the home (see Photo 3.) A defensive attack was used to safely control this rapidly spreading fire. On the Alpha side, the force of the wind pushed fire through the home and out of the window on the left and the front door located on the right (see Photo 4.) Although the front door served as the firefighter's point of entry, it unfortunately also acted as a dangerous vent point for the wind-driven fire.

The Need To Consider The Wind

According to Dan Madrzykowski of the National Institute of Standards and Technology (NIST), the Fire Fighting Technology Group, FFTG, a branch of NIST, completed a seven-year study on positive pressure ventilation (PPV). As part of the study, the FFTG also conducted eight experiments to examine the impact of wind on fire spread through a multi-room structure involving a high-rise building.

Tests conducted determined that an external wind speed of as low as 10 mph could cause a vented room fire within a structure to quickly spread from an apartment unit to a vent point, represented by a stairwell door. The spreading fire had floor-to-ceiling and wall-to-wall fire involvement with blow torch characteristics.

In addition, temperatures within the flow path of fire measured in excess of 1,112 degrees F. These excessive temperatures were determined to be too high for even fully protected firefighters to survive. One aspect of these findings which should be of special concern to all firefighters is that although these results where determined during simulated high-rise apartment fire conditions, the effects of a 10 mph wind can have similar fire results even in residential structure fires; the types of structure fires firefighters respond to most often.

In order to effectively manage the risk or the potential danger, it is a fundamental necessity for firefighters to be made aware of the danger so that it can be properly managed. It is a currently accepted practice for firefighters arriving at the scene of structure fires to consider the associated fireground factors and when appropriate to initiate a fast and aggressive interior attack from the unburned side. When the occupancy is residential, having a potential life safety hazard, an offensive strategy is viewed as the acceptable practice.

In general, during an interior attack from the unburned side, fire and smoke is pushed away from uninvolved portions of the structure by advancing firefighters, thereby providing a means for occupants to exit the structure. However, during seemingly "normal" appearing wind-driven residential structure fires, the firefighters were unaware or did not recognize the potential danger associated with the prevailing wind speed and direction in relation to the position of the fire. In many cases, it ended in defensive operations and in the tragic loss of firefighters when offensive strategies were initially used. If firefighters are unaware of the danger:

  • There will be no situational awareness
  • No one will have a reason to speak up and utilize crew resource management
  • Firefighters will not have the information needed to calculate the risk as advocated by the rules of engagement
  • An accurate risk-benefit analysis cannot be made.

The Wind Factors

During the course of any structure fire, the wind may influence interior conditions and firefighter safety. The wind may:

  • Not be a factor
  • Help firefighters during the interior attack
  • Injure or kill firefighters during the interior attack

Since there is always a possibility that the wind may cause life threatening conditions, without exception, every firefighter must be aware of and must consider the wind hazard on each occasion they respond to a structure fire.

Wind Not A Factor

During working structure fires managed by firefighters on a national basis, and when relatively safe, firefighters will conduct an offensive strategy. During many of these particular fires however, the wind was not a factor. The wind speed may have been light or calm or may have been blowing in a direction which did not act to adversely move the fire within the structure during the incident.

Wind Helps Firefighters

During other structure fires and whether observed or unobserved by firefighters working at the scene, the prevailing wind was actually pressurizing the structure on the Alpha side, the same side the front door was located and which firefighters used to enter and quickly advance into the structure. During these fires, the wind speed and direction, which was at the backs of advancing firefighters, actually helped the firefighters by pressurizing the Alpha side of the structure as well as pushing the smoke and heat in a forward direction and away from advancing firefighters. The wind provided the additional benefit of venting the smoke and heat out of the building through openings on the Bravo, Charlie or Delta side of the structure. The wind also served to cool the interior, reducing the onset of flashover as well as improving visibility to facilitate the primary search.

Wind Injures Firefighters

During certain structure fires, conditions were right for the wind to rapidly push the fire into the structure. Although the point of origin can be on any side of the structure, when the origin of the fire was on the Charlie side of the structure, openings into the structure such as windows were vented allowing wind to enter and spread fire rapidly through the structure (from Charlie side to Alpha side) when a vent point on the Alpha side was created. During a pressurized Charlie side scenario, the vent point was usually the front door which was the arriving firefighters point of entry.

The Wind Trap

In addition to oversight associated with hazards of the wind, another troubling aspect of a fire originating on the Charlie side under pressurized wind conditions has to do with a misinterpretation of the initial size-up factors. In this scenario, smoke and or fire originating at the rear may be visible on the approach or over the roof line from the front of the structure. This condition, at first glance, will appear to be ideal to initiate a traditional fast and aggressive interior attack from the unburned side (Alpha side) while PPVs are set up at the front door to assist in forcing the smoke and heat forward to vent out the Charlie side of the structure.

However, because the wind is pressurizing the Charlie side of the structure and the fire, in reality, when the front door is opened and firefighters advance to locate the fire and search for occupants, they will be met by a fast moving wall of fire having blow torch characteristics and untenable temperatures. Since the fire burning in the area of the Charlie side will follow the path of least resistance, a rapidly spreading flow path of fire and smoke will be established between the open windows on the pressurized Charlie side (the inlet) and the open door on the Alpha side (the vent point). It is also important to note that the use of PPVs at the point of entry will not be able to overcome the pressure created by the wind.

Without a specific warning, an accurate initial size-up, and predetermined strategy and tactics designed to avoid the danger, today's firefighters may easily become a part of a firefighter disorientation sequence from sudden exposure to an extremely dangerous wind-driven structure fire.

Wind Driven Fire Action Plan

In order to avoid wind-driven fires, firefighters may consider the following action plan based on hard lessons learned.

Firefighters must be trained to understand that a wind speed of only 10 mph or greater pressurizing vented fire on a side of the structure can cause sudden life threatening fire conditions on the interior. As a warning and reminder to consider a wind-driven fire condition with a 10 mph wind, dispatchers must transmit the wind speed and direction to responding companies at the time of dispatch. Command must also be notified of any forecasted change in the wind speed and direction and make tactical changes accordingly. A 360-degree walk around should be conducted to determine if vented fire is being pressurized by the wind and on which side of the structure. When a wind driven fire condition is encountered, the situation must be transmitted to all responding companies. When possible and from the exterior, engine companies should quickly attack the fire on the pressurized side of the structure to knock down the main body of fire. When accomplished and if structurally sound, search and rescue crews may enter the structure through the extinguished side to conduct a primary search as other firefighters advance to check for fire extension.

Note: An exterior attack of vented fire on the pressurized side of a structure should be initiated during both rescue and non-rescue scenarios, since as determined by NIST, advancing through an opening such as a door on the opposite side of the structure will create a vent point which will place firefighters and occupants in the dangerous flow path of fire.

Conclusion

When an unfavorable outcome occurs on the fireground, it may indicate a weakness in our method of operation. This is true unfortunately as it applies to the hazards associated with wind-driven structure fires. However, important lessons have been learned by the study of wind-driven fires and the well documented experiences of firefighters who served before us and therefore change is needed. Wind-driven structure fires are special hazards which will require an understanding of the risk and special wind-driven fire tactics which are summarized here.

Preventing exposure to the hazards of a wind-driven fire, of 10 mph or greater, can be accomplished in part by obtaining reports from dispatchers of the wind speed and direction, by controlling the vent points such as windows and doors and ensuring they are kept closed; not allowing a vent point to be created. Finally, by quickly attacking the vented fire on the exterior of the pressurized side of the structure, and not from the unburned side, the risk associated with wind-driven fires may be reduced and may very well prevent the fatality of firefighters.

Special thanks to Mr. Daniel Madrzkowski and Stephen Kerber of the National Institute of Standards and Technology and to the National Institute for Occupational Safety and Health Fire Fighter Fatality Investigation and Prevention Program, (NIOSH).

Note: This article implements Everyone Goes Home, Courage to be Safe Program, Life Safety Initiative 3, Incorporating risk management with Incident Management at all levels including strategic, tactical and planning responsibilities.

WILLIAM R. MORA, a Firehouse.com Contributing Editor, is a former Captain of the San Antonio, TX, Fire Department. William has done extensive research on the topic of firefighter disorientation including the analysis of 444 structural firefighter fatalities and is the author of the United States Firefighter Disorientation Study 1979-2001. You can reach William by e-mail at capmora@aol.com.

 

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