By P.J. Norwood
and Sean Gray
There has been a lot of focus the past few years on controlling ventilation. Controlling the vent point goes against what many were originally
taught and the opposite of what we practiced for many
years. Because of the greater understanding of fire
dynamics and ventilation-induced fire behavior, many
departments, including some of the largest departments
like Los Angeles County (CA), the Fire Department
of New York (FDNY), and Chicago (IL) have adopted
new best practices that have been successfully instituted
on the fireground. Is it perfect? Absolutely not. Do we
still have to use our experience and knowledge to make
intelligent fireground decisions that may go against
what had been previously taught? Yes! However, those
situations should be few and far between.
TO VENT OR NOT TO VENT?
One area that some firefighters have trouble understanding with controlling the vent point is what we’ve
seen and felt on the interior when we don’t open up
and actually shut it down instead. In the past, when
we performed ventilation, we achieved a lift of smoke,
heat, and unburned products of combustion, giving
us a clearer view at the floor level. This lift and clearer
view gave us the ability to work faster and more efficiently by giving us the ability to work in an environment we could see, and it gave us the perception that
it was cooler in temperature. When we do not perform ventilation and instead shut/control doors, we
are allowing the environment to continue to fill with
the smoke, heat, and unburned products of combustion. This places us in an environment that we have
been taught is bad for us and bad for the occupants.
What we can’t see when operating on the fireground
are the things that are truly happening to the gas and
heat levels when we ventilate and when we do not
ventilate. When we ventilate, temperatures will rise.
This rise in temperature is because of the most basic
form of the fire dynamics. Fire needs oxygen to burn.
The more oxygen we provide, the fire gains in size
and intensity. Regardless if the “hole” is a window,
door, or 4 × 4 roof hole, the temperatures will rise
because we are supplying more oxygen.
When we do not ventilate (until water is applied), we
are decreasing the amount of available oxygen. Therefore, the fire decreases in size or slows its growth. This
allows less heat and energy to be created. However, the
smoke and unburned products of combustion will drop
to the floor, exposing a potential trapped victim to poisonous gas. The part that we need further understanding of is what is actually occurring to the environment.
The poisonous gases already exist at levels that can be
deadly, and excess moisture from the burning synthetic
materials already exists prior to water application. The
more heat that is generated by allowing oxygen will
increase the gas concentrations and temperatures that
the victims are exposed to. While visually it appears to
be counterproductive to shut down ventilation, when
we step back and review the data from research studies,
we are increasing victim survivability by controlling the
Research on Governors Island, New York, found that
one of the important outcomes was quantifying how
much more hazardous ventilation can make fire conditions. In one experiment, the first-floor living room was
reignited, creating a fuel-rich, ventilation-limited envi-
Close the Door
Concerns with controlling the vent point
Left: Interior door closed.
Right: Interior door open.
(Photos by authors.)