Tuesday, April 26, 2011

Rules of Thumb: The Safest, Most Effective Path of Least Resistance

To the untrained observer, fire operations, especially during initial phases, may appear to be a disjointed arbitrary set of actions, often bordering on the chaotic. For the undisciplined fire department, this may be more of the rule than the exception. Unfortunately, property loss and civilian and firefighter casualties are often the result.

For the well trained and disciplined fire department operating under a competent Incident Commander, quite the opposite will be true. An effective action plan based on a sound strategy is set into motion through effective communication and coordination. Primary searches are launched in the areas of most peril, attack lines are placed to protect the search, cut off and extinguish the fire, ventilation is conducted quickly and efficiently, allowing even quicker advance of attack lines, and overhaul and salvage operations are carried out so that the structure suffers the least amount of damage possible, in other words, a textbook fire operation.

What is the difference between these two diametrically opposed fireground operations? The simple fact is that textbook fire operations do not just happen by accident. They are a result of training, coordination, and the understanding of the principles that guide the spread of the products of combustion as well as the disposition of the suppression agent used to quench the fire. Knowledge of the enemy is of paramount importance. The fire strategist who can understand the principles that govern the enemy and apply them to the fire situation will more often than not have the upper hand on fire control and understand what it takes to say one step ahead of the incident.

The principles referred to here are governed by the laws of nature. Simply stated, the products of combustion: flame, smoke, heat, and gases will take the most effective path of least resistance upward until they meet a barrier, where they will spread laterally until another vertical channel is found. Then, if they haven’t given up the heat to the surrounding area, they will continue upward. This is why we ventilate natural openings on the roof, to unleash the beast in the most harmless direction.

If one understands and applies strategy and tactics to this rule of thumb, what to do and more importantly, where to do it, begins to come into focus and make more sense. If you are able to figure where the fire will go next, you can take steps to cut it off, in other words, confine it to as close to its area of origin as possible.

Water, our most common weapon against this enemy, will also follow the most effective path of least resistance, although, in the opposite direction. Water will always attempt to seek its level. It will flow vertically downward until it meets a horizontal obstacle like a floor. It will then spread out until it finds a hole or other artery downward and its gravity-influenced path will continue. Understanding this law forms the basis of salvage operations and sometimes surround-and-drown incidents.

The task of the Incident Commander is to intervene on behalf of the fire forces (the Good Guys) using these same paths of least resistance to stop fire damage. Placing personnel armed with the proper resources in these paths of least resistance will often affect the outcome of the fire incident in a positive manner. Fire operations, of course, must incorporate safety into the equation. Safety must always be the overriding concern of all fireground operations. The rule of thumb then, utilizing this concern for safety as the common strategic and operational thread that guides fire operations then becomes “the safest, most effective path of least resistance” to accomplish the objective.

Take for example a second floor fire in a corner building. The front door is on Side A, but there is also a door on Side D. Heavy fire venting from windows have caused power lines to drop in front of the building and are blocking the front door. While the most effective path of least resistance may be the front door, it is no longer the safest due to the presence of the fallen wires. In this case, the safest, most effective path of least resistance is via the door on Side D.

Let’s look at a typical scenario of a four-story multiple dwelling of ordinary construction with a fire on the second floor. The most basic operational goal is to protect the interior stairs. Why do you suppose that is? Because it is not only the most effective path of least resistance for the upward spread of the products of combustion, but also, the safest, most effective path of least resistance for occupant egress. In addition, it is also the safest, most effective path of least resistance for the attack operation. In fact, one of the problems often faced is the logjam encountered as lines are being stretched up the stairs at the same time that occupants are attempting to escape down the stairs. Fighting for and maintaining this artery will afford the greatest amount of occupants the best chance for a speedy evacuation from the building. If for some reason this artery is jeopardized such as by an apartment door left open, allowing the fire to spread into the path of least resistance (the stairwell), evacuation would most likely turn into rescue as occupants become trapped on upper floors or are forced to use other areas of egress, such as fire escapes. In fact, the more occupants must deviate from the most effective path of least resistance out of the building, the more dangerous the situation becomes, the longer it takes and the more personnel required to make it happen.

In the next blogs, we will take a look at some of the common fireground conditions and operations to see how this rule of thumb can be universally applied

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