(NIST) Fire Fighting Tactics under Wind
Driven Fire Conditions Experiments
Synopsis
This study consisted of a series of 14
experiments conducted in a seven-story
building to evaluate the ability of positive
pressure ventilation fans, wind control
devices, and external water application to
mitigate the hazards of a wind driven fire in
a structure.
Each tactic was evaluated individually and
in conjunction with the others to identify
the benefits to firefighters and occupants in
the structure.
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.
Departments may need to vary in the
methods of deployment 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.
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Findings
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Wind is a factor. Wind (or air) can
significantly increase the thermal hazards
of a fire in a structure.
Smoke is Fuel. A ventilation-limited (fuel
rich) condition developed prior to the
failure of the windows.
Venting does not always equal cooling.
Wind velocities within the structure
exceeded 5 m/s (11 mph) due to 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. Thermal conditions
in the flow path were often higher than
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400 ºC (752 ºF) and were not consistent
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 stairwell on the fire floor is closed, it
limits the spread of fire and heat will be
limited and wind driven “blow torch”
conditions will be prevented. If the door
to the fire room is closed, the fire spread
is limited.
Use of PPV. PPV fans could not overcome
the effects of a wind driven condition.
However when used in conjunction with
door control, Wind Control Devices
(WCDs), and Floor below nozzle (FBNs)
(tactics that stop the wind driven
condition) the PPV fans were able to
maintain tenable and clear conditions in
the stairwell.
Impact of WCDs (Wind Controlled
Devices).
The WCDs reduced the
temperatures in the corridor and the
stairwell by more than 50%. The WCDs
also completely mitigated any velocity
due to the external wind. The WCD must
cover the window opening completely to
be effective. 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 all
cases, the water flows suppressed the
fires. This demonstrated that a relatively
small amount of water directly applied to
burning fuels in the fire compartment
from a safe location can have a significant
impact.
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Takeaways
This study provides background information to help firefighters employ the following tactics as
applicable. Please note that these findings are not limited to high rises, and some takeaways
can be applied in one-to-two-story structures as well.
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Wind driven conditions can occur with as little as a 10mph wind
Wind needs to be considered part of the initial size up
Flow path can be controlled by limiting ventilation
In wind driven fire scenarios, it is more important to use the wind to your advantage and
attack the fire from the upwind side of the structure
Unexpected ventilation from a broken window can suddenly change the interior thermal
conditions
Read the Reports
Fire Fighting Tactics under Wind Driven
Conditions: Laboratory Experiments NIST
TN 1618
http://www.nist.gov/customcf/get_pdf.cfm
?pub_id=901104
Simulation of the Dynamics of a WindDriven Fire in a Ranch-Style House – Texas
NIST TN 1729
http://www.nist.gov/customcf/get_pdf.cfm
?pub_id=909779
Fire Fighting Tactics Under Wind Driven Fire
Conditions: 7-Story Building Experiments
NIST TN 1629
http://www.nist.gov/customcf/get_pdf.cfm
?pub_id=902177
Simulation of the Dynamics of a
Wind-Driven Fire in a Ranch-Style House –
Texas NIST TN 1729 PowerPoint
presentation
http://www.nist.gov/fire/wdftexas.cfm
NIST Wind Driven Fire Presentations
http://www.nist.gov/fire/fwdgi.cfm
Wind Driven Fire Research: Hazards and
Tactics. Madrzykowski, D. and Kerber, S.,
Fire Engineering, Vol. 163, No. 3, March
2010
http://www.fireengineering.com/articles/pr
int/volume-163/issue-3/features/winddriven-fire-research-hazards-andtactics.html