Fireground Flowthrough

The Order of Operations

©2012 Christopher Brennan         

Fireground Flowthough as a concept is simply a particular way of examining the often-discussed “Coordinated Fire Attack.”  The efforts of attack, ventilation, and search crews must be coordinated to bring the fire under control and maximize the ability of firefighters to save lives and property; this idea is not new.  What has changed on the macro level is the time frame in which we have to control the environment.  Additionally at the micro level, the level of individual departments and agencies, we see a host of variables from staffing to dedication of assignments to assignment of work outside the scope of “fighting fire.”  With these changes comes a need to critically re-examine what a Coordinated Fire Attack looks like.

Fire Dynamics

            I have written about the current research into modern fire dynamics before (You Have to Be Aggressive) and there is a host of information that can be learned from reviewing the information that Underwriter’s Laboratory (UL) has released.

            In summary, what we can see based upon full-scale experiments using one and two-story homes built in UL’s testing facility is that the interior of a fire building, by the time of fire department arrival, is generally a ventilation-limited environment.  This means that there is an abundance of fuel and a lack of oxygen to support combustion.  Compartmentalized fires (any fire inside a building is a compartmentalized fire) become ventilation-limited when the growth of the fire has consumed the available oxygen in the building.  The fire then enters an initial decay phase.  This is often occurring before the arrival of the fire department.  The fire, if left unventilated, will decay to the point of self-extinguishment.  However, if the building is ventilated, either by failure of a construction element (like a window) or by outside influence (Firefighters opening the front door) while there is still a fuel-rich, high-heat environment, fire will rapidly grow and reach flashover.  

            Based upon the UL tests we can see that the lowest known times from opening of a ventilation-limited building fire to conditions becoming untenable for firefighters was 72 seconds in a one-story, 1200 square foot, ranch style home, and 100 seconds in a two-story, 3200 square foot home with an open floor plan and high ceilings.  By method of comparison, UL also studied the time from ignition to becoming ventilation-limited and then reaching flashover after ventilation with a legacy fuel package made up of ordinary combustible materials.  In the one-story, 1200 square foot ranch it took 21 minutes to become ventilation-limited and 8 minutes 30 seconds to reach flashover once the building was opened. 

LEGACY FUEL PACKAGE VIDEO

The incidents in which we have seen firefighters being caught in rapidly changing fire environments are likely due to this compressed timeline.  Our ability to predict what will occur (a key element of Situational Awareness) is no longer valid. We must undertake to train our personnel to operate under the new “time clock.”

The Clock

            The generally accepted “play clock” in the National Football League is 40 seconds.[1] This means that the team which controls the ball has 40 seconds from the time a play is completed to snap the ball for the next play to begin.  NFL Quarterbacks have both a visual clock to watch and have established a mental clock through years of practice.  In the 2011 regular season, Drew Brees of the New Orleans Saints had the best pass completion record of all NFL Quarterbacks at 71.2 percent.[2]  If in the 2012 regular season the NFL changed its rules and reduced the play clock from 40 seconds to 5.2 seconds (roughly equivalent to the amount of time our fireground play clock has been reduced), I would expect to see that completion percentage fall drastically; that is until Mr. Brees had sufficient time to both adapt his mind to the new clock and adapt his team to a more time-compressed environment.

            We must adjust to the new fireground play clock.

Order of Operations

            As grade school students we begin to learn that mathematics requires us to perform a certain order of operations: work the arithmetic in the parenthesis first, then perform any multiplication and division, and finally perform any addition or subtraction.  The order of operations ensures consistent, accurate results.  A student who performs an addition function before multiplying across will not get the correct answer.  The modern fireground also has an order of operations.  In the case of an offensive mode of attack (entering the burning structure) that order looks like this: Control the Air then Control the Heat

            Firefighters are taught from their very introduction to the topic of fire behavior about the fire triangle and the fire tetrahedron.  On the fireground, we need to think about our ability to influence the fire triangle.  In order for combustion to be sustained there must be fuel, oxygen, and heat.  We cannot influence the fuel package; it was defined before our arrival.  Considering that the modern compartmentalized fire is reaching a ventilation-limited status around five minutes after ignition. In many situations we are arriving on scene once a fuel-rich, high-heat environment exists.  Our first concern must be to control the ventilation profile of the building: Control the Air.  This has the effect of allowing us to control the play clock.  We can see from the video below the impact keeping the door partially closed has on the clock.

DOOR CONTROL VIDEO

We have to understand that in a compartmentalized fire there is a massive amount of energy trapped in the building during the initial decay phase.  There is a misconception that if we just “vent enough” we can confine the fire to the fuel package and prevent flashover.  While this is possible in burn towers where fuel packages are rigidly defined, it is far less likely in the real world.  Any ventilation increases the probability that flashover will occur if we don’t address the second step in our order of operations: Control the Heat.

Controlling the heat is simply another way of saying that we are controlling the energy.  When we begin to cool the atmosphere we are cooling the super-heated, oxygen-starved fuel.  There are various modes of operation and tactics that can be used to achieve this.  We can use an offensive fire attack, a transitional attack, or a purely defensive attack.  In the case of the transitional and defensive attack we are electing to control the heat first.  When we chose an offensive attack we must control the air while we advance into the structure and begin controlling the heat.

There are several primary actions that must be addressed when we are operating in the offensive mode.  While the specific order of execution may vary, they must always be conducted with the priorities already discussed: Control the Air, Control the Heat.

  • Entry
  • Cover and Confine
  • Ventilation
  • Search
  • Extinguishment

Entry is the first step that we have to undertake.  In the offensive mode we are gaining access to the seat of the fire through the interior of the building.  When we enter we are changing the ventilation profile of the structure and altering the time clock.  If there is already ventilation we are increasing the speed the clock is running.  If the building has not yet been ventilated we are starting the clock.  Upon entry we need to control the door, both during the forcible entry operation, and during the hose line advance.

Cover and Confineis the process of getting a hose line to the seat of the fire.  This serves two purposes: first, we are controlling the atmosphere, cooling the superheated gasses at the ceiling as we advance; second, we are working to stop the spread of fire as ventilation increases.  Nozzle teams must begin controlling the atmosphere during their advance, flowing water to the ceiling.  This cooling action is done to prevent the super heated fuel over head from finding enough oxygen to begin free burning.  The idea that we should not flow water on smoke is outdated; the smoke is the fuel and it is ready to begin free burning the moment it has enough oxygen, unless we cool it (Control the Heat).

Ventilation may occur through the action of the fire department entering, breaking windows, or opening the roof; through action or inaction on the part of an occupant or bystander, such as leaving a door open; or because of the energy of the fire itself, such as a window failing because of heat.  During the initial attack we must control this ventilation because in controlling the route of air (oxygen) to the fire we are controlling the fire until the atmosphere can be sufficiently cooled.  It has to become ingrained in the actions of our personnel that any opening made will cause the fire to intensify until water is flowed on the seat of the fire.  Once the nozzle team is prepared to knock the fire, coordinated ventilation operations serve to create a safe method of allowing the heat and pressure to escape away from the nozzle team.

Search operations are critical if there is the potential to save lives.  In this case we are referring explicitly to what has been called “Primary Search”.  Search operations must not be conducted in an uncontrolled environment.  We can control the environment in one of two ways: we can cool the atmosphere or we can isolate the compartment.  When we increase the ventilation of the space by opening doors or windows to the exterior of the building we create an area of negative pressure, a flow path that will draw the fire to that opening.  If a crew is going to be performing a targeted search, entering from the outside (Vent, Enter, Search or VES), care must be taken to not create a flow path until a firefighter is prepared to enter the building and isolate the compartment by closing the door.  It is worth considering that while some departments will commence a primary search through the front door while the nozzle team is preparing to advance – using an isolation tactic by reclosing the front door, this requires the search team to be in a position that has the greatest likelihood of becoming untenable if the nozzle crew has difficulties in advancing.  A targeted search may be preferable because of the greater ability to isolate the search from the seat of the fire.

Extinguishment occurs when the attack team reaches the seat of the fire and cools the primary fuel package below the point where pyrolysis stops.  Once we have reached the seat of the fire and stopped the decomposition of the solid fuel package into combustible gasses, we have controlled the unrestrained fire and can begin addressing secondary concerns like secondary searches, overhaul, salvage, and other support functions.

We must consider a fireground order of operations if we are to begin developing simple and adaptive, effective and efficient SOGs for fire attack.  No article, author, or instructor can give you a checklist for fireground operations that can be applied mindlessly or robotically.  What we can do is use the science of fire dynamics and address, in a broad manner, means of establishing a relatively safe operating environment.  We must control the air then control the heat if we are going to operate inside a compartmentalized fire. 


[1] http://www.nfl.com/rulebook/timing  accessed 2 May 2012

[2] http://espn.go.com/nfl/statistics/player/_/stat/passing/sort/completionPct accessed 2 May 2012

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