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Fire Attack
The Royer Nelson Formula is highly suitable for fire attack since it is not restricted to one time of 30 seconds. There are an infinite number of products of time and r.o.f. that equal the right amount of water to fill a room full of steam. However, because most fire fighting is restricted to room size fires, we are restricted to a narrow range of times and flows. Let’s consider time first.
We already know from research by Royer & Nelson at Iowa State University that a maximum of 30 seconds is the time needed to control almost all confined structure fires. What is the minimum? An effective fog attack requires that water be distributed throughout the fire area. The method devised by Royer & Nelson to do this is to insert the nozzle inside the room and rotate the nozzle rapidly clockwise as many times as needed to knock out the flames until condensing steam appears. This will take about 10 seconds. That is the minimum time. Let’s take the minimum and maximum times and calculate the corresponding flows for a 2,000 cubic foot (56,6 cubic meters), an average size room.
| Gpm x t = Vol/1,5 | Lpm x t = Volm/1,5 |
| Gpm x 0.5 = 2.000/1,5 | Lpm x 0,5 = 56,6/1,5 |
| Gpm x (0.5/0.5) = (10/0.5) | Lpm x (0,5/0.5) = (37,7/0.5) |
| Gpm x 1 = 20 | Lpm x 1 = 75,4 |
| Gpm = 20 | Lpm = 75,4 |
Now let/s calculate with t = 10 seconds or 1/6 of a minute (0.166 minute)
| Gpm x 0.166 = 10 | Lpm x 0,166 = 37,7 |
| Gpm x (0,166/0.166) = (10/0.166) | Lpm x (0,166/0.166) = (37,7/0.166) |
| Gpm x (0.5/0.5) = (10/0.5) | Lpm x (0,5/0.5) = (37,7/0.5) |
| Gpm x 1 = 60 | Lpm x 1 = 227 |
| Gpm = 60 | Lpm = 227 |
Thus we need to consider times between 10 seconds and 30 seconds, and flows between 20 gpm (75,4 Lpm), and 60 Gpm (227 Lpm) for room size fires. The Royer Nelson formula gives you all the information necessary to make a powerful fog attack on confined room sized fires.
For larger fires involving more than one room of a structure there are several ways to make an effective fog attack.
