Rate-of-flow formulas for larger fires
Now how large a structure can these fire flows provide the needed fire flow?
Warren Kimball looked at data supplied by fire departments (brigades) that reported the actual fire flows at its largest structure fires. The data revealed that the NFF necessary and sufficient to control and extinguish such fires averaged around
4 gpm per 100 ft3
Warren Kimball stated the rate this way so that he could use an integer for the gpm. However, with the availability of hand calculators, it is not necessary to stick to integers. So let’s change this rate to “per cubic foot”.
0.04 gpm per 1 ft3
This statement is a complex or compound quantified statement. Not only is the gpm quantified, that is, true not just for one minute, but for the second minute, and so on for every minute, but also this number itself is quantified as being true for not just one cubic foot but for every cubic foot. So let’s write the rate as
(0.04 gpm) per 1 ft3
The formula for calculating the NFF for a given size structure is the rate (r) multiplied by volume (V) equals the NFF.
R x V = NFF
R, of course, is a constant (0.04 gpm).
0.04 x V = NFF
With this equation we can calculate the NFF for any size structure. Let’s do this using the data from the preceding table.
| Fire Flow Applied | Number Personnel | Number Pumpers | Volume |
| 1,000 gpm | 15 | 2 | 25,000 ft3 |
| 2,000 | 30 | 4 | 50,000 |
| 3,000 | 45 | 6 | 75,000 |
| 4,000 | 60 | 8 | 100,000 |
| 5,000 | 75 | 10 | 125,000 |
| 6,000 | 90 | 12 | 150,000 |
The first entry is the volume of a 2,500 ft2 house one story with a height including attic space of 10 ft. The second entry is the volume of a two story store 25 by 100 feet with a 20 foot height. Each of these entries represents community or commercial building that are commonly found in most communities.
