If 70 bar is consumed by the heaviest breather during the exit portion of a first dive, what is the required completion pressure for the second dive?

To determine the required completion pressure for the second dive when 70 bar has been consumed during the first dive, it's essential to understand the concept of gas management in diving, particularly for cavern diving where safety margins are critical.

The completion pressure refers to the minimum cylinder pressure that must be maintained at the end of a dive to ensure that the diver has enough gas for emergencies, including a safe ascent and mandatory safety stops. When diving, particularly in a cavern environment, divers often anticipate the gas consumption of the heaviest breather, ensuring that they account for this when planning subsequent dives.

In this scenario, if the heaviest breather consumed 70 bar during the exit portion of the first dive, it suggests that the diver required that amount of gas to safely complete the dive. To ensure safety for the second dive, divers typically plan to have a reserve above what was used in the previous dive as a precautionary measure.

Therefore, a common practice is to have the completion pressure for the second dive be double the consumption of the heaviest breather from the first dive. In this case, 70 bar consumed would lead to a doubling to 140 bar as the completion pressure for the second dive. This provides adequate gas reserves while taking into consideration