InDepth magazine has a recent article by Stratis Kas regarding the Rule of Thirds, and it makes the case it just won't work in no flow conditions when someone has a catastrophic loss of gas. The main reason for this post is to correct the general equations describing his suggestion for something better that he calls an Adaptive Reserve Gas Model. He gives both metric and imperial versions (also attached), but both yield different answers than his numeric example therein (which is correct, BTW). In general, I like the central message that one should be inflating the SAC on exit, and he gives his suggestions for how to do that. In keeping with the spirit of a "divisor", I've rearranged the corrected general expression to use a penetration factor:
The penetration pressure (metric folks) or volume (imperial folks) is simply the starting pressure (or volume) divided by F. His example of n=3, Sd=45% increase, and Sr=100% increase (i.e., the SAC doubles) results in F = 3.45, which is seen in Section 5 of each PDF.
F = 1 + (1+Sd) + (1+Sr)/(n-1)
where Sd and Sr are the inflation factors for donor(s) and receiver, and n is the number of divers in the team. Intuitively, this can be viewed on a diver basis asF = [entrance] + [inflated exit] + [portion provided to the OOG diver]
The penetration pressure (metric folks) or volume (imperial folks) is simply the starting pressure (or volume) divided by F. His example of n=3, Sd=45% increase, and Sr=100% increase (i.e., the SAC doubles) results in F = 3.45, which is seen in Section 5 of each PDF.
