Command-ment #4: Thou shall ensure that four sides are seen and compared. The American Heritage Dictionary of the English Language (fourth edition) offers the following definitions of "size-up": to make an estimate, opinion or judgment; to arrange, classify, or distribute according to size; the...
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Time - Time is a critical component of an intelligent and safe fireground operation. Basically, time means how much offensive time you have to preserve value. Another important consideration is how much time you have before unprotected structural members fail. Thus an important determination at a contents fire or structure fire. A simple rule of thumb is wood char: wood will char 1/8-inch with every five minutes of direct flame exposure (smoke will not char wood). Thus, wood will char Â¼-inch with 10 minutes of direct flame exposure, 1/2-inch with 20 minutes, one inch with 40 minutes, and so on. (Important: Depth of char is for each side of the wood exposed to fire.) Again, these are rules of thumb. However, it's easy to see why a five-by-18-inch glue-laminated timber will resist fire longer than a truss comprised of two-by-four-inch plate connected sticks.
Size - Size refers to the size of the operation. What size operation will be required to preserve the value you've identified? Fireground operation "size" has two components: water and people. Even though you may determine that there is possible occupant and property value, without adequate resources (water and people) an intelligent and safe tactical intervention may be impossible. You may determine that there's more value in one area of a building than in another.
In our craft, as in any craft, numbers are important. A fire requiring 5,000 gallons to extinguish will not be controlled with 10 2Â½-inch hoselines. Likewise, a fire requiring 50 gallons of water to extinguish will not be controlled with a continuous flow from 10 eye-droppers. Regardless of the value or time, the operational mode and action must match the size of the problem.
If you can assemble lots of people, a good rule of thumb is that a fire requiring 500 gallons per minute (two 2Â½-inch hoselines) is probably the largest (size) fire that can be attacked offensively. If you are a small department with not many people, you need to lower your strategic expectations; the offensive number should be reduced to 300 gallons per minute or less. Bottom line: doing this simple math is crucial strategic information.
"Big Six" Size-Up
On the fireground, any urgent tactical problem will fit into one of six categories â€” the "Big Six":
1. Fire - Is fire showing? Where is fire showing? From what side and on what floor? Fire in the attic? Fire in the basement? Floor below?
2. Smoke - Is smoke showing? Where is smoke showing? From what side and on what floor? Smoke from the attic? From the basement? The floor below?
3. Verified occupants - You have compelling evidence that occupants are viable occupants. Verified occupants may require rescue or simply need evacuation.
4. Possible occupants - You determine the status of life safety is literally "unknown if occupied." "Unknown if occupied" means primary search.
5. Exposures - Are adjacent occupancies that are threatened? If so, where? Are there interior areas that are threatened?
6. Access - Apparatus access, forcible entry, key box, ladder access, long hoselay, etc.
The Big Six are easy to remember and establish a foundation for your action plan. During size-up, one Big Six component that has helped many fire officers manage emergency incidents is listing problems before making tactical assignments. During size-up, only problems that are urgent and can be fixed tactically are listed. A lightweight truss would not be listed because it is not a tactical problem; a strong wind would not be listed as a tactical problem. Both are strategic problems that can influence the operational mode and the action plan.
Using abbreviations - F for fire, S for smoke, V for verified occupants, P for possible occupants, E for exposures and A for access - listing tactical problems does not take a lot of time, literally just a few seconds. Problems are listed as they are observed and are not prioritized as they are listed. The problem list will be prioritized when solutions are identified. Tactical problems and solutions, dovetailed with strategic problems and the determination of risk versus value, is called an incident action plan.
Your list of problems establishes a tangible foundation for your operational mode and for your initial action plan. By listing problems, you ensure that nothing of strategic importance is overlooked. Listing the Big Six requires that you slow down and look. (If you are attacking fast, you are not looking.) The Big Six focuses on the identification of problems related to your strategic priorities: life safety and incident stabilization. The Big Six does not address salvage, overhaul or support objectives such as water supply or utility stabilization.