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Determining Turnaround Using Tables
The basic steps involved in using a tablebased approach to determining gas turnaround are the same as they are for divers using identical cylinders: identify the controlling diver; determine penetration gas volume; and, calculate turnaround for individual team members. The difference is, we now base our calculations on actual volume instead of pressure.
 Identify the controlling diver — Consult the cylindercomparison table to see which team member has the lowest actual starting gas volume.
Example: Diver A’s steel 95 is filled to 2,400 psi, which the table indicates is 86 cubic feet. Diver B’s aluminum 80 is filled to 3,100 psi, which the table tells us is 81 cubic feet. This makes Diver B the controlling diver.
 Determine penetration gas volume — The controlling diver should determine his or her penetration gas supply using pressure, then convert this value into the equivalent volume, in cubic feet. Other team members should consult the table to see what this volume of gas would be in their cylinders, expressed in psi.
Example: Diver B’s penetration gas is represented by a pressure of 1,000 psi or — according to the table — 26 cubic feet. Diver A’s penetration gas volume must be represented by a number that is equal to or slightly less than this; according to the table, this is 25 cubic feet, or 700 psi — 300 psi less than it is for Diver B.
 Calculate gas turnaround for individual team members — Using the equivalent penetration gas pressures determined in the previous step, each team member deducts the appropriate number from his or her actual starting pressure to determine gas turnaround.
Example: Continuing the previous example, Diver A’s turnaround is 1,700 psi; Diver B’s is 2,100.
Some cave divers who use dissimilar cylinders avoid doing precise gasturnaround calculations because they are intimidated by the complex mathematics they believe are required. As you can see, however, consulting a simple table can greatly simplify the necessary math and help reduce the possibility of mathematical error.
