What repetitive group designator do you use when ascending to altitude?

• A. The highest repetitive group designator obtained in the previous 24-hour period
• B. The lowest repetitive group designator obtained in the previous 24-hour period
• C. The average repetitive group designator
• D. The most recent designator from the previous dive

Answer: (A)

The amount of nitrogen left in your tissues after dives is tracked by a repetitive group designator, and altitude changes the risk profile because lower ambient pressure slows off-gassing. To stay safe when ascending to altitude, you plan using the most conservative estimate from the last 24 hours—specifically, the highest repetitive group designator obtained in that period. This accounts for the peak nitrogen loading you could have carried from any dives within the day, ensuring you don’t underestimate decompression risk as you ascend. Using a lower, average, or only the most recent designator would not reflect the full potential nitrogen load from previous dives, which could lead to unsafe planning.