Articles, Blog

Examining Fire Fighting Tactics under Wind-Driven Conditions (Pt. 3)


So now it’s time to get
the meat out, right? You have heard
our stories. We’re here to tell the fire
stores and the motivation and to make the connection, but you have really got to
hear from the guys that… the meat, all right? We are going to start with
Dan, I believe, all right? Let him introduce himself
in terms of his background and his part in the study and we will get to the
bread-and-butter in this stuff. Thank you Pete! Another piece that
came together was an opportunity
for DHS grants. Department of Homeland
Security offered grants for research for
firefighter safety, the fire protection
research foundation, part of the NFPA, I happened to get one of
these teamed with NIST and our team here, to start looking at wind-driven
conditions in a laboratory. Now you guys say, well, we don’t
fight fires in a laboratory. There are certain things
we have a hard time measuring and understanding
in the field. We knew we needed
to go to the field to do some burns
and buildings, but before that we wanted to
start off in an environment that we could control and that we could make a
lot of measurements on. What we really wanted to do
was measure temperature. Everybody always wants
to know how hot is it, because they sort
of have an idea when their face
piece might melt, they have an idea about when
their turnout gear might burn, so everybody wants to
know how hot it is. They typically don’t ask
what’s the heat flux, but we want to tell them
because that’s the energy that’s being
transferred to you and temperature is just the
end result of energy, right, that’s just our
way of saying how much energy was
transferred to you, how much energy
is in your skin, or how much energy is
in your turnout gear, that’s basically what
we use temperature for, that’s the end result. What you want to do is control
the energy and where it goes, so you need to have a better
idea of what the energy is. Pressures, if you are
going to use fans to control the fire flow, what’s the pressure
that’s being developed, what’s the build up and
those sorts of things; and last but not least
the heat release rate, where does the
energy come from, it comes from the
furniture that’s burning, it’s coming from the interior
finish, the carpeting, wall-covering materials,
things like that. So we want to get some idea of
how much energy is available in a typical space,
in a typical room, what do you need to
flash over a room. So that’s what we are
going to do in our lab. Once we get those baselines,
that baseline information, we want to say
what might work, and one of the tactics
that was proposed is wind control device, either a blanket
or a curtain and I will show
you some of those, basically it goes back to the
same old fire triangle, right? We need oxidizer,
we need a fuel, we need heat to
have a fire, break one of those legs,
fire stops, what the wind control device do,
smothers the fire, you put a blanket
over the broken window, smothers the fire,
it wouldn’t work. What about introducing water
from the floor below the fire, so that if the firefighter is
trying to shoot water upstream and they can’t
really get the water toward the energy is
being produced anyway unless that post stream
can make a 90 degree angle once it gets 30-40 feet
down the hall and go into the
fire apartment, they’re really not
doing anything, but torturing themselves, they are not able to get
the water where they needed on the fuel, put the fire out. So we look at what can you
do from the floor below, what impact
might you make. The blankets tend to be a
little larger than curtains, that’s the distinction and I’ll
show you a test with each. Again what might it do? Well, it should block the
effects of the wind, it should take
the oxygen away. Exterior water application, they are not going to have
much effect on the wind; however, it should
cool the fire gases, should reduce the
production of heat, and that’s certainly a
very positive effort. Before we run the
experiments in NIST, we first look at the fuels that we are going to
put into the apartment that we’re going to build. And so how are we going
to start our fires? We want to do things
very repetitive, so we can repeat them one
experiment after another, and so the first
thing we do is we are going to start our
fires with a trash can, a little small
plastic container, we put a little bit
of newspaper in it, light it on fire with
an electric match, you can see it burning there,
in the top image, that’s around 30 kW, 30-40 kW
fire, pretty small fire. We light a chair, we get a
number of identical chairs. Basically we have two
tractor-trailer loads, full of furniture from an
old hotel roll up to NIST, and that’s what
we are using, so we have
replicate furniture for each of the eight apartments
that we are going to burn and the chairs are giving us
1.8 MW or 1800 kW, 1.8 MW, and you see the chair in
the next picture down, and that’s quite a bit
of fire coming off of it, so you can imagine one of
those chairs in your house and you have six foot
flames coming off of it, imagine that,
your living room. Then we go to the sofa, and these were again
where it’s hotel… sofas from a hotel, so they don’t have a lot
of plush padding on them, but they’re still not too bad. 2.5 MW was the average
peak heat release rate that we are getting
off the sofa. In this image here, the bed, king-size bed, very
comfortable, very plush, fully involved little
over 4 MW of energy. Anybody know what it would
take to flash over a room, typical residential
scale room? Around 2 MW. So basically, two
chairs more than enough for maybe even one chair with a little bit of
latex paint on the walls would be good enough
for some carpeting, one sofa or half a mattress would be enough to
generate enough energy to flash over a typical
residential scale room. So now that we know that
what our fuel load is, we set up an apartment, and we have a bedroom where we are going to
start our fire every time. It’s 12 feet x 16 feet. If we go down a
12 foot hallway, we have a target room, and that door is closed
for each of the tests. In the first couple of tests,
we used a hollow core wood door, and then we went
to a steel door. The hollow core
wood doors failed rather quickly on
us as you will see. Living room, again
12 foot x 16 foot. This door, typically, in seven of the eight
experiments was open, because what we are
really after here are what are the
conditions in the corridor. When we start a fire here and we introduce a wind and
the fire fails that window, what happens out here? This corridor is 24 feet
in this direction, notice that this
direction is closed. There is no flow. In this direction,
we have a ceiling vent, that’s the same size
as the door opening, 36 inches x 80 inches. So we have flow
in this direction on the north side
of the hallway, and I will be showing
you some data later that looks at differences between the north side,
the flow side, and south side where we have no flow, as well as different conditions
throughout the space. Montgomery County allowed us
to use one of their airboats and we were typically generating
15 to 20 mile an hour winds, you don’t need
excessive wind here against this window,
during the experiments. We did eight experiments;
one with no wind, just to look and seeing how the fire would spread
through our apartment, then we start looking at some
with just a control device. We had some challenges, in controlling the
fire in our laboratory and then we decided, you know, we really need to
start introducing some water and here to start
cooling this off and you will see
some examples there. And then the last
three experiments, we didn’t use any
wind control device, but we’re looking at how we might use a water
spray from the floor below to see how the wind might
carry the water droplets and have an impact or not. One of the thoughts was, what happened if you had a fog
nozzle from the floor below and you just shot it
straight in the air, so it would go
cross the window. Would enough water droplets
get blown in the window to have some impact? And then other ones were
looking at a smoothbore actually introduced
into the room; bouncing it off the ceiling, and sort of becoming a
large de facto sprinkler. So this is a scene of what
you will see on the DVD. It basically is showing you
where the cameras are located, so we have one
on the outside and these are the views that
you will see on the DVD. Eight different scenes; we have eight different cameras
in each of the test setups and it goes through
and shows you the IR camera in the
corridor, for example, shows you each view and shows you where the
cameras are located. So that when you’re
watching the experiment, you have a better sense for
what’s actually happening. And then we had to cameras
in the target room there, IR camera and a video
camera collocated. So experiment two, we are basically going to
use a 10 foot x 12 foot fire resistant material, a wind control device,
or a blanket, drop it over the window, as soon as we get
the fire established and spread through
our apartment. So you notice that
the fire started and we can see it
from the window, in our bedroom view we
see the flames starting to extend to the ceiling. This is your real-time
down here in the corner so we are a little over
a minute 50 seconds, we have sped this up
by a factor of four, in the interests of time to sort of speed things
up for you a little bit. Where you see the heat is
coming out in the corridor and life is pretty
good right now, right? If you are in the corridor,
you can crawl under that and your turnout gear,
but what just happened? The window failed. And look at that heat now; some of the firefighters that were burned in the
Vandalia incident, described it as a blowtorch
coming out of the door from floor to ceiling. That’s all they could see. They couldn’t make any
movement against it. And certainly, that
is in fact what we saw once that window failed. Now watch here, we took the
oxygen away for a while. It reduced the
intensity of the fire. We removed the wind control
device let the air back in, and what happens,
fire intensifies again. Smoke is fuel, right? We are controlling
the oxygen and that’s how we are
going to control the fire, you’ve got to keep
that vent closed, but you still have
the fuel in there. It’s still pretty warm, now
how are we going to cool it? This is another view of
that same test again, just to sort of what the area
around when our window breaks and look what’s going on at
real-time in the corridor, and once thing you
notice is the flames typically have to
impact the window, touch the window to transfer
enough energy to the window to get it to fail, but before window failure,
again things aren’t bad, but as soon as
the window fails, things go bad in that
corridor very, very quickly, within seconds. And as it was
alluded to before, this is the kind of situation where you are going
to go down to cover up and you are not
going to get back up. It just happened so fast, it’s transferring so
much energy to you, and what’s going
on with the fire? We are blowing in there,
15-20 miles an hour and yet the flames are still
coming back against the wind. This is exactly what the
roof man in Vandalia saw, but we didn’t understand
it at the time, we didn’t understand the
issue with the overpressure. Experiment five; in this case, we are using a
small curtain, 6 foot x 8 foot. Again, this is something that instead of having maybe
four firefighters to operate, you could do it with… if you needed to one firefighter
above the fire floor to drop it down. We have a got it pre-staged
on top of the roof here and we have two
firefighters pull it down. So again we
start the fire. We have a new interior in
this between each test, new furniture
between each test, we’re trying to replicate our
fire development every time. So again we have
the fire building, we have our hot gas layer,
developing in the bedroom, smoke starts to spread, and get
into the living room area. It starts to come
out the doorway. We start to see a
little bit of smoke coming into the
corridor here, but we still don’t see any
heat coming in the corridor, the smokes cooled off and as the fire
continues to grow, we now start to see the heat
coming out of the doorway into the corridor. We can see some heat
being pushed around the target room doorway, the window fails,
conditions change, flames through the bedroom, we will see flames going
through the living room, flames out the doorway,
into the corridor, some cases, you don’t even
see the flames in corridor, heavy black soot remains
heavy black soot, but the energy
is in that soot, the high temperature is
there, lethal conditions, even in full turnout gear. We drop the curtain, we’ll start to see the smoke in
our lab clear up a little bit. One minute after we
deployed the curtain, we started a 30 gallon
per minute flow and a sprinkler that was
mounted at the window to start cooling
the fire gases that are still
trapped in there, and then we’ll go ahead
and take that curtain down and what we see is
the fire is out now. We have got
complete control, some steam generation in addition to limiting
the induction of fresh air, we have smothered fire,
cooled the fire gases enough, that the fire is out. We are going to start
to get some image back in the thermal imaging
camera a little bit and there we always see
is some smoke and vapor in the fire apartment. Here is test seven,
just a small clip. Again the fire is building
up, we fail the window. Here the door to the
corridor is closed. So what you see now,
are leaks around the door, a small opening in the keyhole and you see how hot
gas is being pushed under the door,
around the door. We still have flames
blown back out. Now what we’re going to do is
we let this happen for awhile and then we are going
to open the door. So this shows you that there
are some things you can do to move your hand around, even if you can’t
see it’s better if you have a thermal
imaging camera, obviously you’ll see
something like this. But don’t just
go opening doors. Or if you open doors,
only open them a little bit, on a windy night, open the door fully, boom! Untenable conditions in the
corridor within seconds. Very dramatic change, so door control is
very, very important. Engineering terminology, what does that look
like for temperature? What I’ve got here are
temperatures in the bedroom, topline, the living room,
the next line down, corridor south and
corridor southwest, those are the areas, that do not
have flow, the non-flow side and then corridor
north is the flow side, and that’s this line here. Time zero is when
we open the door. So we can say that
opening the door not only affects conditions
in the corridor, these three portions
of the graph, but also affects the temperatures in
the bedroom as well. Initially it cools things off,
a lot of fresh air comes in, it’s fuel rich and then the fuel
and the air mix come together and we go from conditions that are under 600
degrees Centigrade or basically under
a 1000 degrees and then jump up to things
that are in excess of 1500 °F. Notice that the living
room follows soot and the flow portion
of the corridor tracks with them very well. The non-flow portion
of the corridor remains in a much
cooler temperature. Many of the line of
duty death incidents that we work with NIOSH and other fire departments
to investigate, end up with a condition where the firefighters
ended up between the fire and where the
fire wanted to go, and that’s a
bad place to be. And in many cases they
ended up in that position, based on how the fire
department vented the building or doors that they opened or a path that they…
a flow path that they made. This is the last test
we did, test eight. I am showing you the beginning
of this introduction, because we moved
some of the cameras. In this case, we have got
a video camera outside, as well as a thermal imaging
camera looking at the window and we also have a camera
up looking at the vent, at the smokestack and that’s going to be
important in our test. The rest of the cameras for
the bedroom and the living room and the corridor arrangement are in the same place as
the previous experiments. So experiment eight; again everything
starts off the same. One of the differences
here as you notice, we reinforced the ceiling. This is the target where we are trying to
aim the hose stream, we are trying to get a certain
angle on the solid stream that we are going to
introduce from outside and bounce off the ceiling and look at the impact that
it might have on the fire and the conditions
back in the corridor. Another thing that we are
going to look at here, which we learned in
a few tests earlier was that if we let
it go long enough, all the hot smoking gases that are coming out
of our structure, eventually will get to
enough concentration and mix with enough air that they’ll ignite in our hood,
above the structure, quite an exciting
thing in a laboratory, and we will see that. So again the window fails, fire spreads through
the bedroom, through the living room, out the doorway,
into the corridor, untenable conditions
for firefighters and fully protective
clothing in the corridor. The fire continues to pulse
out over-pressurizing. Even though we are
blowing wind in the room, we still get
flames coming out, and notice how they sort
of form a star pattern and that kind of thing. As we start to burn
up our cameras and lose different
piece of equipment, watch what’s going on here. We’ve ignited all
the fire gases, the smoke that’s
collected in our hood and now we are going to
start throwing water on it, and as soon as we
start to apply water, watch what happens to the fire,
out within seconds. So it is having a
dramatic effect. It may not look
like it here. We’re not getting water on a
lot of fuels that are burning, but we are
taking the gases that are collected
at the ceiling, the gases that are moving
through the structure and cooling them enough
that they can’t burn, very significant improvement. Just sort of a summary, so here’s the four
experiments that we did with wind control devices, both large and small and you see that we had
heat release rates, before we deployed
the device in the range
of 15 to 20 MW. So basically two rooms
of furniture burning and spreading out
into that corridor; some of the heat coming
back out the window. Time zero is when we deploy
the wind control devices, and what do you see happen? Within 20 seconds, right, significant decrease in the
energy being produced; we’re dropping from 20 down
to below 5 within a minute. What about the temperature? These measurements are
made in the corridor and these are made at 3
feet above the floor. This is on the flow side,
on the north side, so it’s sort of
the worst-case and what do we see again, at temperatures here that are
above 6000C or above 11000F, you drop the wind
control device and very rapidly
within 60 seconds, those temperatures are
reduced by more than 50%. How about that heat flux, the energy that’s
hitting your gear, your face piece,
your helmet, causing it to heat up? Again, conditions
that are untenable, to give you a benchmark, your gear is tested to
84 kW per meter squared to get a TPP rating of 35. It has to protect
you for 17 seconds. Now remember, that’s gear,
that’s clean, that’s done in a laboratory,
ideal conditions. When your gear is preheated, your gear is compressed,
your gear is dirty, you really have 17 seconds
even when you get hit with that, you get hit with
that kind energy, again you’re
not getting up. Look how it reduces it. In less than a minute,
drops it down to levels that your gear will
protect you for some time and allow you to move. Impact of hose streams,
test eight, we got up to 30 MW when we
ignited the gases in our hood, hitting it with water,
drops it down pretty quick, not as great impact
with the fog nozzles or the straight stream
in here, because why, we still have the
air pushing in there, we still have burning
back in the living room, we have got carpet burning, we have got a lot
of gases burning. If we take this out
another two minutes, we have more impact, but initially we don’t have
a tremendous amount of impact with the hose streams as far as heat release rate
reductions concerned. What about temperature? Well, we can see that
with the solid stream, we are getting deeper
penetration into the apartment and therefore we are
getting better cooling than just trying to
flow a fog nozzle across the window or
just into the window, it’s only having an
impact in the bedroom, it’s not having much impact
way out in the corridor. So in that case the smoothbore
certainly does better job. Heat flux, again smoothbore
reduces it a little more than basically no impact from having a fog line
in front of the vent. So what do we learn? Well, we have an idea what some
of the heat release rates are from some upholstered… different kinds of
upholstered furniture, we demonstrated some
basics, smoke is fuel, venting does not always
equal cooling, right? When the window broke did
conditions get cooler inside? No. Temperature increased,
energy increased. Be aware of the flow path,
where is it, and control it
or stay out of it, control the doors, whether you are controlling
the door at the stair, open it just a crack,
and see what’s going on. Wind-driven fire flows generated
on untenable conditions for fully protected
firefighters in a very short
period of time. The wind control devices we saw
reduced the thermal hazard and stopped the
wind effects, the water streams did some
to reduce the thermal hazard, but do nothing for
the wind effects and that’s why we need
to go to a real building and really get a
good understanding of what’s going on. Do you love this stuff? I love watching
you audience the first time they see that
door open and boom! Right? Floor-to-ceiling
sustained… not sustained 1200-1300
degrees floor-to-ceiling, coming at you right
now like that. What do we teach our
firefighters, right? Control the door, get the
charge two-and-half inch wide, get ready to go,
everybody ready to go, okay, open the door. Done, done, right? We didn’t see it coming, we’ve got to learn to
see it coming, right? Do you like the people,
you think, you see it pushing, I don’t have a people,
make a people, right? [inaudible] make a people, see what the wind
is doing, right? There is even more,
there is better to come. I know it’s getting late,
but stick where it is, because there is more to
come, it gets even better.

Leave a Reply

Your email address will not be published. Required fields are marked *