Rate-of-flow formulas for Confined Structure Fires
One of the most important questions relating to fighting fires is the following.
How much water is needed to fight a given fire?
Immediately it should be recognized that the answer to this question varies as the size of the fire. The bigger the fire, more water is needed to control or extinguish that fire. Also the answer varies as the type of fire (Class A, B, or C), as well as the type of structure involved (ordinary or noncombustible) Thus we are dealing with complex answers to a simple question.
It is necessary, therefore, to narrow the question be able to get an answer. Let’s narrow the question to ordinary Class A fires that are confined in a structure. Thus our question becomes,
How much water is needed to fight ordinary confined structure fires?
The definition of a confined structure fire is one in which the ceiling or roof is intactConfined structure fires are the type most frequently encountered by all fire departments (brigades), and are of greatest concern for life safety and property conservation. The definition of a confined structure fire is one in which the ceiling or roof is intact. This definition means that a fire can be burning out a window(s) or a door(s) and still be a confined fire.
There is an answer to the previous question. Before considering this answer, however, we must introduce some elementary mathematics. Elementary mathematics does not mean the math that is taught in elementary schools, but the algebra that is taught in high schools throughout the United States and in other countries at the same level.
Thus we must study the rate-of-flow formula (equation) to answer our question of how much water is neededFire departments do not have the means or capability of dumping all the water needed onto a fire all at once. We use nozzles that flow water over a period of time. At the end of that time enough water will be projected into the fire to control it or extinguish it. The time involved may be very short (seconds) for confined fires. For a large structure in which fire has burned through the ceiling and roof (open fire), the time involved may be hours. In either case water is flowing at a certain rate for a certain period of time. Thus we must study the rate-of-flow formula (equation) to answer our question of how much water is needed.
