Which cylinder size is most appropriate for a dive requiring 90 cuft of breathing gas?

To determine the most appropriate cylinder size for a dive requiring 90 cubic feet of breathing gas, one must consider both the size of the cylinder and the pressure it can hold.

The S100 cylinder filled to 2800 psi can be calculated to provide sufficient gas by using the formula which relates cylinder volume and pressure to the total amount of gas available. The S100 cylinder, having a capacity of 100 cubic feet, when filled to 2800 psi, would yield:

Total gas = Cylinder volume × Pressure

Total gas = 100 cuft × (2800 psi / 3000 psi)

Total gas = approximately 93.33 cuft

This calculation shows that the S100 cylinder can supply more than the required 90 cuft of gas, thus making it suitable for the dive.

In contrast, the other choices do not meet the requirement as effectively either due to being smaller in capacity or lower in pressure, resulting in less gas than what is needed for the dive.