Why should you add percentages together when tracking your CNS exposure during multiple dives?

Adding percentages together when tracking your Central Nervous System (CNS) exposure during multiple dives is essential because it helps ensure that you stay within the safe limits established for oxygen exposure. This is particularly important when using Enriched Air Nitrox, which contains a higher concentration of oxygen than regular air.

Oxygen has a toxicity effect that increases with pressure and exposure time. When you conduct multiple dives using Nitrox, each dive contributes to your cumulative CNS oxygen exposure. By aggregating the percentages, you can monitor your total exposure against the safety thresholds, which helps prevent potential neurological effects related to oxygen toxicity.

Using this method allows divers to maintain awareness of their cumulative exposure, assisting in making informed decisions about future dives while minimizing the risks associated with excessive oxygen levels. This practice is crucial for diver safety and overall health during repetitive dives.