A group of Advanced Open Water Divers conducts two dives with a surface interval. What is crucial in determining the ending pressure group after the second dive?

To determine the ending pressure group after the second dive, it is essential to consider both the depths of the dives and the duration of the surface interval. The depth of a dive affects how much nitrogen is absorbed by the body; deeper dives lead to higher nitrogen absorption due to increased pressure. Similarly, the duration of the surface interval plays a critical role in allowing some of that absorbed nitrogen to off-gas, which can reduce overall nitrogen levels in the body before the next dive.

Combining these factors provides a comprehensive picture of a diver’s nitrogen loading status. For instance, if divers conduct deeper dives but have a short surface interval, they may still retain a significant amount of nitrogen. Conversely, a longer surface interval can help reduce these levels, depending on the depth of the first dive, and this interplay creates a more accurate assessment of the diver's risk of decompression sickness.

By considering both the depth of the dives and the duration of the surface interval, divers can more effectively manage their exposure to nitrogen, ensuring a safer diving experience and properly determining the ending pressure group.