Original post found at: http://community.fireengineering.com/profiles/blog/show?id=1219672%3ABlogPost%3A630841
The fire ground is a highly dynamic environment that is layered with varying degrees of complexity and uncertainty. Each incident we face will present its own set of variables, which must be specifically accounted for, and addressed accordingly – especially in regards to ventilation. As the late Lt. Andy Fredericks (1996) once wrote, “…ventilation parameters are highly variable and may change many times during the course of a fire.” DC Emanuel Fried (1972) similarly stated that “Every building has its own ventilation problems. What may be the correct ventilation technique in one building may not be proper for another.” Therefore, the size-up process must include a (continual) assessment of the fire’s ventilation profile. Paul Grimwood (2008) defines this term as, “the amount of air available within a compartment” – determined by the location and amount of existing ventilation points. Once it has been identified, the appropriate interventions can then be determined and properly executed. Doing so will also aid in the critical task of assessing the fire’s rate of growth and its direction of travel; as fire burns proportionately to the quantity of air which it receives (Braidwood, 1866).
By its very name, ventilation has always been predominantly focused on the exhaust component, when in reality, equal attention must be placed on the intake. Because today’s fires are so overly fuel-rich, their development and spread are almost exclusively dictated by the availability of oxygen within the compartment. Therefore, by temporarily restricting its supply of air (without inhibiting vital operations), until the onset of fire extinguishment, the fire can be kept in a ventilation-controlled state – promoting decay. As Steve Kerber (2011) states, you want to “limit the air until you gain the upper hand.” Any open, horizontal opening must be viewed as a source of ventilation and a means for feeding air to the starving fire. Fried (1972) asserted “Never ventilate a fire that may intensify because of the ventilation until charged lines are in position;” except in matters of life safety (i.e. VES). Whenever we open a door to make (forcible) entry, we are also creating a ventilation point. We must understand that doors are actually the most effective means of horizontal ventilation, as they span nearly the entire height of the wall; allowing fresh air in and hot gases out. Simply leaving a door open (without a charged line present) can be the catalyst for rapidly reenergizing and/or spreading a vent-limited fire; as was the case in the 2008 close-call in Prince George’s County, Maryland, among countless others.
The recent fire dynamics research has conclusively shown that the fuel load of today’s fires, exacerbated by energy efficient materials and construction, is producing tremendous heat releases rates and resulting in the following detriments: faster fire propagation; shorter time to flashover; greater propensity to become ventilation-limited; and increased volatility (Kerber, 2011). Because the progress of the fire’s development has been accelerated, the impact of ventilation is now even more profound. Despite popular belief, this concept is not at all new. In fact, Andy Fredericks (1996) discussed this topic almost twenty years ago in his Fire Engineering article Thorton’s Rule, stating: “…when ventilation is increased, another factor must be considered—the rate at which different materials liberate heat…when provided with increased ventilation, hydrocarbons generally will liberate heat at a rate faster than cellulosic materials. As a consequence, we can expect that rollover and flashover conditions will be achieved in much less time.” The common denominator among the aforementioned conditions is they collectively lead to a diminished operational time frame (unless we intercede); placing greater emphasis on controlling the movement of air—managing the flow path.
While flow path management has seemingly taken the fire service by storm over the last five years, it is not a recent discovery. The terminology may be different, but the concept and its associated tactics have been around for 150 years. James Braidwood (1866) was a pioneer of his time, responsible for many significant advancements in firefighting. He published, arguably, the first document on the subject of flow path (air track) and isolation procedures, (i.e. door control) which read as follows:
“In the first discovery of fire, it is of the utmost consequence to shut doors, windows, or other openings. It
may often be observed, after a house has been on fire, that one floor is comparatively untouched, while those
above and below are nearly burned out, this arises from a door on that particular floor having been shut, and the
draught [air track] directed elsewhere…The men of the fire brigade were taught to prevent, as much as possible the
access of air to the burning materials. What the open door of the ash-pit to the furnace of a steam boiler, the open
street door is to the house fire. In both cases, the door gives vital air to the flames. The door should be kept shut
while the water is being brought, and the air excluded as much as possible.”
Managing the flow path can be as simple as closing an open door or window until the arrival of a charged hose line. The fire service has been preaching isolation procedures (door control) for decades, when engaging in vent-enter-search (VES); so much so that the letter “I” (isolation) has been added to the acronym (VEIS). Yet, the same cannot be said for other fireground operations, especially traditional (interior) search. By simply closing the door upon entry, the room becomes isolated from the area of involvement, preventing further contamination, offering protection from fire spread and allowing windows to be vented, if the situation warrants it; enhancing tenability and orientation, as well as providing an alternative means of egress/victim removal. Fredericks (2000) described how a veteran, ladder company lieutenant from the Bronx advocated for door control during the primary search at apartment fires, stating “The calming effect on a growing fire that results from the simple act of closing the door behind you can be quite astonishing.”
There has been an apparent reluctance to fully accepting door control and other flow path management techniques. Much of this can be attributed to its association with the perceived movement against ventilation. This misconception has likely derived from the use of such terms as “anti-ventilation.” When taken at face value, it becomes easy to understand why; as Aaron Fields always says, “words matter.” Anti-ventilation, developed and implemented in the UK, utilizes “zoning” tactics in an effort to confine the fire and isolate it from the rest of the structure. It does not denounce ventilation; it simply calls for a delay in its use (“unless the incident commander has identified a viable objective or reason to create openings”) until the fire has been controlled. While its application as a primary strategy has been effective for our brothers across the pond, its success, however, is largely in part to the building construction which they face (differing from which is found in the US); as it “relies on the stability of the compartment to keep the fire in-check” (Grimwood, 2008).
Despite the differences, Paul Grimwood of the London Fire Brigade, saw that there were many components that would prove beneficial as a supplement to the American style of ventilation – giving birth to the concept of “tactical ventilation” in 1987. Grimwood came to this revelation while on detachment with the FDNY’s 7th Division (South Bronx) in the mid-70’s (the “War Years”) and volunteering on Long Island. He went on to say, “I acknowledged that the general concept of opening up buildings under specific circumstanceswould reap great rewards, providing the strategy was applied with a clear purpose, or intent, and the actions of firefighters were organized, disciplined, and controlled.” Experiencing the two approaches first-hand in their respective environments, exposing the significant differences (i.e. the presence of combustible void spaces), he recognized they both had merit and possessed their own pros and cons. By fusing their basic principles and adapting them accordingly, he arrived at a middle-ground, tactical ventilation: the venting or containment actions used to take control in an effort to gain tactical advantage during firefighting operations (Grimwood, 2008).
Venting, in essence, is fundamentally a matter of control; of both ourselves and the air flow within the compartment involved in fire. The actions we take, or lack thereof, will dictate the survivability of victims, the fire’s progression and the well-being of firefighters. DAC John Norman (2008) poignantly explains this dynamic metaphorically (paraphrased for brevity): Whoever controls the supply of oxygen wins the battle. For if it is allowed to fall into the hands of the enemy at the wrong place, it will use it to grow stronger, possibly with explosive speed. The commanders who master the art of warfare known as ventilation have a great force on their side. Ventilation, when executed tactically, is not the problem; quite the contrary, as it ispart of the solution. The real problem is a lack of fireground discipline. By applying the Four Tenets of Tactical Ventilation (Informed; Deliberate; Coordinated; and Controlled), those engaging in ventilation operations will possess the insight and wherewithal to be successful and ensure any actions taken support the mission – preserving life and property.
Fredericks, Andrew. (1996, November). Thorton’s Rule. Fire Engineering.
Fredericks, Andrew. (2000, March). Little Droplets of Water: 50 Years Later, Part 2. Fire Engineering.
Fried, Emanuel. (1972). Fireground Tactics, 1st Ed. Chicago, IL: H. Marvin Ginn Corp.
Grimwood, Paul. (2008). Euro Firefighter. United Kingdom: Jeremy Mills Publishing.
Kerber, Steve. (2011). The Impact of Ventilation on Fire Behavior in Legacy and Contemporary
Residential Construction. Retrieved from file:///C:/Users/npapa/Documents/Fire/References/UL%20-%20Impact%20of%20Ventilation%20on%20Fire%20Behavior%20in%20Legacy%20and%20Contemporary%20Residential%20Construction.pdf
Norman, John. (2008). Fire Officer’s Handbook of Tactics, 4th Ed. Tulsa, OK: PennWell.