When making multiple dives, what do you need to track regarding the CNS "clock" limit?

Tracking the CNS (Central Nervous System) "clock" limit during multiple dives is crucial for ensuring diver safety. The correct approach is to add the percentages of oxygen exposure together from each dive, ensuring that the total does not exceed 100%.

When using enriched air nitrox, the increased oxygen content can lead to higher toxicity levels, particularly affecting the CNS, which is why it is important to monitor cumulative exposure to oxygen across multiple dives. Each dive exposes the diver to a certain percentage of the CNS limit based on the depth and the percentage of oxygen used. By summing these percentages, divers can effectively gauge their total oxygen exposure and maintain safe diving practices.

This concept emphasizes the need for diligent tracking of cumulative percentages rather than any mathematical operations that would not accurately reflect the overall exposure levels, which is why simply adding the percentages is the correct approach for keeping within the CNS limits on multiple dives.