Are fog nozzles not the answer?
Fredericks further recommends a minimum of 150 gpm fire flow for residential fires, and 250 gpm for commercial fires. If you read all of Fredericks article, I think that you will realize that there is nothing in the entire article that justifies these recommendations. The reason why is simple. Fredericks does not have a formula that can tell you how much water is really needed to control or extinguish a given size fire. Remember Nelson’s fundamental principle:
In principle fire fighting is very simple. All one needs to do is put the right amount of water in the right place and the fire is controlled.”
The most creative contribution of Royer and Nelson is the discovery of the Iowa Rate-of-Flow Formula. This formula is based upon two scientific facts: (1) One gallon of water expands to 200 cubic feet of steam. (2) One gallon of water absorbs all the heat produced by the oxygen in 200 cubic feet of air.It is quite remarkable that both facts validate the same number, 200. The Iowa rate-of-flow formula, generalized with time as a variable is:
NFF x t = Vol / 200
where NFF = Needed Fire Flow in gpm, t = time in minutes or fraction of a minute, Vol = volume in cubic feet, and 200 is the Iowa constant.
Let’s do one simple calculation of the right amount of water. Let’s Take an average size room, say 2,000 cubic feet. To distribute the little drops of water, let’s take the minimum time of 10 seconds, or 1/6 of a minute. Substituting these numbers into the formula gives
NFF x 1/6 = 2,000 / 200
The fraction 2,000/200 = 10 gallons—the right amount of water. So multiplying both sides of the equation by 6 produces the answer.
NFF = 60 gpm
Only 10 gallons of water is needed for fire control, and a flow of 60 gpm brings fire control in 10 seconds.
