Frank Brannigan Was Wrong...

Bold words from some random guy blogging, I know but I think I am onto something here.  Francis Brannigan, a Fire Protection Engineer who many of us know from his writing on building construction and his classic text Building Construction for the Fire Service, used to say, "The Building is your enemy; know your enemy!"  He was wrong.  The Building is the battleground, it is the terrain in which we and the enemy do battle.



Fire is the enemy and fire behavior is a predictiable indication of how the enemy will behave.  If we look at line of duty death and injury statistics we see far too many of our brothers and sisters being injured or killed because of fire development.  Just last week Mark Falkenhan-FF/Medic, Lutherville Volunteer Fire Company, Baltimore County FD was killed after being trapped in what sounds like flashover conditions. On Sunday a woman and three firefighters were injured at a building fire in Springfield, Virgina.

The video below show us the progression of the fireground.  Dave Statter has some good comments about this over at his blog.



We can get into a debate (I suppose) about exactly what fire behavior we are seeing.  It is not a backdraft.  It is not a smoke explosion.  This is a rapid spread of fire because of (probably) ineffective ventilation techniques. I'm not going to launch into some Tactics diatribe here because I do not know exactly what occurred at this fire.  I don't know if this was a townhouse type building where the second floor was a different occupancy.  I don't know if they pulled up with a two person Engine and one person on the Truck.  Something different did have to occur for that fire to be vented in a way that prevented the spread of fire over the heads of the attack team.

What we can talk about is the fire progression and why the fire spread was predicable.

Look at the smoke conditions at the start of the video.  This entire building is heavily charged.  The structure of the building is involved.  The fire is deep seated.  Based on info from http://www.wunderground.com the temperature was in the low 20's(F).  The somewhat "lazy" nature of the smoke once it is outside the building is due to the temperature. The key factors though should be the volume of dense smoke we see and the color.  We have to recognize that if it was 65 degrees outside this smoke would push away from the building with great velocity.  In this case it is "pushing" out pretty hard but then hanging more than we would normally expect from a hot fire.  WHY?  Because the "fluid" that is unburned products of combustion carried by heat contracts and slows when it hits that cold air.

Something worth considering is the inherent relationship between temperature and pressure.

How well do your firefighters understand Boyle's Law and Charles's law of fluid dynamics?  I know, I know, that's HazMat... right?  Maybe I'm biased to looking at this through a lens of Chemical and Physical properties because I just got back from a validating committee for a HazMat Technician Text Book.

Charles's Law simple says that as temperature increases so does pressure in a closed container.  Boyle's Law tells us that if you keep temperatue constant as pressure doubles volume halves/ as volume doubles pressure is halved.  In other words if you give a fluid more space the pressure is lessened, if you give it less space pressure increases.  Here is where they come together. As temperature is building because of unrestrained fire the pressure in the building begins to increase.  If the building was perfectly sealed that increase in pressure would eventually smother the fire by consuming oxygen.  If it cools off the fire goes out and all the unburnned products of combustion just congeal on surfaces.

However, once we allow the building to ventilate (in any manner) we create a place for that "fluid" to go.  However because it is a small opening relative to the amount of product temperature and pressure continue to build.  The exiting "fluid" is heated but to rich to burn (I know, more HazMat).

At the 1:45 mark you can see flame in the C/D corner window on the D side (if you call the front door side of the building where the truck is parked A).  In 15 seconds heavy fire is venting out the window.  30 seconds after the flame is viable we can see through the A/D corner window the fire is extending.  Three seconds later (2:14) the unburned fuel that is exiting the front lights up.  Once it lights up you will notice that the smoke is moving a lot faster up and away.  That's because the heat is now outside and overcoming the slowing/contracting effect of the ambient temperature.

We MUST study these fires and understand what is happening in the building.  I was in Tulsa over the weekend and spent a few minutes talking with Ed Hartin who teaches extensively about Compartment Fire Behavior Training  Ed is a Fire Behavior guy.  We talked about how it is the lack of knowledge about Fire Behavior that is getting us hurt and killed on the fireground.  While fire behavior may not be predictable with 100% accuracy I venture to say if you are a student of this trade we can get close to 95%.  We don't know until we are inside the compartment what effect the layout may have on fire growth and spread.  However we should understand intuitively what the smoke conditions are telling us about the growth, stage, and location of the fire.

The building is the battleground, and warriors going back as far as Sun Tzu have taught us how important it is to understand the terrain. The ENEMY though is the fire.  You can know all you want about the terrain but if you do not know what the ENEMY is going to do you will still end up killed.  The Fire is Your Enemy, Know You Enemy; The Building is the Battleground, Know the Terrain.