The
momentum of knowledge streaming in from research by the National
Institute of Standards & Technology (NIST) and Underwriters
Laboratory, (UL) combined with such agencies as the International
Society of Fire Services Instructors (ISFSI) needs no introduction.
Firefighters and commanding officers everywhere have experienced what
high-level technical research can now prove to us; the buildings
reaction to fire in the modern box is different from that experienced
by generations before us. Echo the words of one undeniably passionate
instructor, Peter Van Dorpe, Chief of Training at the Chicago Fire
Academy, “everything about the built environment has changed”.
A decade
ago few could have envisioned the new wave of fire terminology that
changes in building construction would bring to fire sciences. Words
such as flow path, heat release, ventilated limited, and “the
spike” were rarely heard. And, as is still the case today, were not
included in the commercial fire curriculums used by most fire
training academies. Modern firefighting demands everyone involved
understand the knowledge behind the new terminology, and more
importantly that everything that happens on every side of the box has
a direct and immediate impact on the flow path and in turn - fire
behavior inside the box.
As a
fire commander, when you pull onto a reported fire scene and see
little or nothing showing always ask yourself “at what stage of
the fire are we arriving”. Know the time it takes from the moment
the air brakes are set to the time your crew will have water ready to
attack the fire. You might arrive post initial growth and the report
of “little smoke showing” is masking a ventilation limited fire.
Enter into the box of a residential fire, whether VES without
immediate isolation or an aggressive attack through the front door
and the result will often spawn an immediate secondary growth of a
ventilation limited fire; termed by many as “the spike”. The
spike occurs when a secure and ventilation limited “box”, the
residential home your crew is about to enter, is violated. The air
fed to the fire due to the violation, causes the ventilation limited
area to flashover. Temperatures during the ventilation limited
flashover caused by this second growth phase will often spike to over
1000 degrees in less than ninety seconds.
Modern
commanders need to know how their commanding actions outside the box
are going to impact the flow path and resulting fire conditions
inside the box. Commanders must be prepared for an immediate change
in fire behavior and conditions. If your crew reports “its getting
extremely hot in here” order an immediate evacuation. Those words
are a red flag that your crew has entered a ventilation limited area
and the area will spike. Additionally, the high degree of heat
release is negatively impacting the structural components of the
building and global failure, usually a ceiling or floor collapse, is
imminent. Study research noted by Dan Madrzykowski of NIST and Steve
Kerber of UL and you’ll understand the impact of our tactics on
ventilation limited fires: how to better recognize them and how to
prevent firefighter death and injury due to them.
Change
happens, whether a decade of research and a few definitions, or a few
seconds of fire attack and a resulting flashover. Know where you and
your crews are at all times, both inside and outside the box.
Additionally, know at all times how you and your crews actions, both
inside and outside the box, will impact the flow path, heat release
rates, ventilation, and the resulting building behavior.
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