Can you switch between NITROX and air diving?

• A. Yes. Enter Table 9‑8, Residual Nitrogen Timetable for Repetitive Air Dives, using the repetitive group designator. If the repetitive dive is an air dive, use Table 9‑8 as is. If the repetitive dive is a NITROX dive, determine the EAD of the repetitive dive from Table 10‑1 and use that depth as the repetitive dive depth
• B. No, cannot switch between NITROX and air diving
• C. Only for trained divers
• D. Only when on a deep dive

Answer: (A)

You can switch between air and NITROX in a repetitive dive sequence, but you must translate how much nitrogen is already in your tissues and apply the right table steps. The Residual Nitrogen Timetable is used to manage the remaining nitrogen from previous dives, and you indicate your repetitive dive with a designator on that table.

If the next repetitive dive is on air, you simply use the Residual Nitrogen Timetable with the repetitive group designation and treat the dive as an air dive, using the table as it is.

If the next repetitive dive uses NITROX, you first convert the planned repetitive depth to its equivalent air depth using the surface-interval table for nitrox (the EAD, from the nitrox table). Then you use that EAD as the depth in the Residual Nitrogen Timetable. This accounts for the reduced nitrogen loading from the nitrox mix and ensures you aren’t exceeding limits across the sequence.

The idea is that nitrox changes how much nitrogen you take up, so you adjust the repetitive dive depth via EAD and still rely on the same residual-nitrogen framework to stay safe. It isn’t limited to trained divers or only deep dives, and it isn’t correct to say you can’t switch at all—proper conversion and table use make the switch safe.