By Warren Whitley and John Taylor
Fire behavior training in America is generally limited, but there are signs of improvement here and there. Did you know that the Virginia Department of Fire Programs curriculum for firefighter and officer training requires a grand total of three hours of fire behavior training? That is the sum total from Firefighter 1 through Officer 4. It is almost like sending an Army officer through four years of West Point or Sandhurst with only three hours of infantry training, definitely not good preparation for battle.
The lab work includes the use of a “doll house” that demonstrates the fire behavior phenomenon on a small scale and emphasizes two important facts: (1) Smoke burns and (2) if you control the air, you can control the fire–Air Track Management (ATM). There is also a backdraft demonstration unit constructed from a 20-foot sea container (photo 1).2 This prop allows students to safely view extreme fire behaviors and observe the positive (over-pressure) and negative (under-pressure) air tracks and the time it takes fresh air to mix with the rich, hot smoke and develop into a backdraft. From there, the students spend time in the fire behavior container that many fire departments erroneously refer to as a flashover “simulator.” We point out that there is nothing simulated about it: Real fire behaviors occur in the containers.
Prince William County is in the process of constructing a large vent container that will allow practicing the fire attack using an ATM firefighting nozzle and ventilation techniques appropriate for the given fire scenario under study; emphasis is placed on recognizing the fire behaviors as they present during the evolution.
The realistic nature of these ATM firefighting techniques demands the highest levels of safety to facilitate realistic and responsible Compartment Fire Behaviour Training (CFBT). Toward that aim, our ATM instructor courses will from the outset follow the curriculum of the United Kingdom (UK) CFBT Instructors Award.3
One of the major additions to the knowledge base of the firefighters in Prince William County involves the extension of the CFBT curriculum–that is the exploitation of the under-pressure or negative air track, a concept covered in detail in Smoke Burns. (1)American firefighters are familiar with the buoyant nature of the hot smoke and fire gases and know about the neutral plane, but they fail to account for the negative path of fresh air coming in to feed the fire. For a fire that has already vented itself through an opening, such as a window, there will be significant clues as to from where the fire is getting its air, and those clues can give a knowledgeable fire officer a wider selection of safer tactics and better information for determining whether to risk an interior attack..
There are a couple of “thou shall nots” in the American fire service that need debunking and should be replaced with accurate fire behavior knowledge. One is attacking from the unburned side. By understanding the under-pressure or negative air track and how it can be used to carry water fog droplets to the seat of the fire and then be used in tandem with gas cooling to knock down, or even extinguish, the fire quickly, attacking from the unburned side is not always the best option.
A quick scenario illustrates a point about the under-pressure or negative air track: You are the officer on the first-arriving engine. You start your size-up walk around the building–a 2,500-square-foot rambler (single-story) house in suburbia. You see that the fire has vented itself through the front window and it is blowing out the entire window from the windowsill upward. You notice the front door is open, hopefully, because the occupants have escaped.
Diagram No. 2.
In Diagram No. 1, you can see where the over-pressure or positive air track flame front was filling the entire front window, indicating the under-pressure or negative air track was coming from below the windowsill through the lower part of the door opening. The first-arriving officer “read the fire,” noted these signs, and decided to introduce water fog droplets into the lower half of the front door and then attacked from the window as the flame front retreated. (See Diagram No. 3).
(2) Photo courtesy of the Prince William County (VA) Department of Fire and Rescue.
WARREN WHITLEY, M.I.Fire.E, CFOD, is an assistant chief with the Prince William County (VA) Department of Fire and Rescue and has more than 28 years in the fire service. He holds a MPA from VA Tech and an MA from the Naval War College.