What principle dictates the breathing gas supply limits during dive planning?

The principle that dictates breathing gas supply limits during dive planning is the Rule of Thirds. This method is commonly used in dive planning to ensure a safe approach to managing gas supplies. The Rule of Thirds involves dividing your total gas supply into three portions: one-third is allocated for the descent and exploration of the dive site, one-third is reserved for the ascent, and the final third is reserved as a contingency for emergencies, such as dealing with equipment issues or the need for additional breathing gas.

By utilizing this approach, divers can minimize the risk of running out of gas during the dive and ensure that they have enough supplies to manage any unexpected situations that may arise. This method enhances safety by providing a structured way to allocate gas, promoting prudent planning and risk management in cavern diving scenarios.

The remaining principles, while they have their applications, do not provide the same level of balanced allocation that the Rule of Thirds does. The other rules like the Rule of Eights, Rule of Halves, and Rule of Quarters focus on different aspects or ratios that do not pertain specifically to the allocation of gas for descent, exploration, and emergencies in the context of dive planning.