When making multiple dives, what must you do with the percentage of the CNS "clock" limit?

The percentage of the Central Nervous System (CNS) oxygen toxicity clock is an important consideration for divers when making multiple dives using enriched air nitrox. Each exposure to oxygen at increased pressures adds to the cumulative risk of oxygen toxicity. Therefore, when calculating the CNS clock limit for several dives, it's essential to add the individual percentages from each dive together.

By doing this, divers can ensure they do not exceed the total CNS toxicity limit of 100%. This cumulative approach helps divers to stay within safe exposure levels, reducing the risk of experiencing harmful effects from oxygen toxicity during or after their dives. If divers were to subtract percentages from 100% or only monitor the last dive's percentage, they would not account for the total exposure and could inadvertently exceed safe limits. It is crucial for divers to monitor their total nitrogen and oxygen exposure throughout multiple dives to ensure their safety.