# Seems overly complex

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Posted by roakey on September 05, 2001 at 08:49:52:

In Reply to: Gas Volume matching posted by Joe R on September 05, 2001 at 01:36:55:

If you have two dives diving rule of thirds and one has a 95 and the other has a 104 (I'm using single cylinders for simplicity), you find 1/3 of the smaller kit:

95 / 3 = 31 cf.

So you turn when either diver consumes 31 cf of gas.

Now one formula fits all:

[(working_volume - turn_volume) / working_volume] * working_pressure = turn_pressure

Assuming LP cylinders without overfills (and overfilling/light filling hardly adds any complexity):

[(95 - 31) / 95] * 2640 = 1780

For the 104s, same thing:

(104 - 31) / 104 * 2640 = 1860.

There ids NO NEED (except of course for dive planning) to calculate RMV/SAC/whatever when volume matching. You just turn when 1/3 of cf of the smallest capacity cylinder is consumed by any diver.

Why does it take two pages to describe this?

Roak

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