The Actual Dive Time (ADT) is the time from the start of the dive to the beginning of the ascent. For no-decompression dives, it does not include ascent time. For decompression dives or dives with a safety stop, it counts from the start of the dive to the start of the safety stop or first decompression stop.
Total Recurrence Time (TRT)
The total repetitive dive time is the repetitive dive time after deducting the residual nitrogen time from the previous dive. If a repetitive dive requires only a one-minute safety stop, the actual repetitive dive time is calculated by subtracting the residual nitrogen time from the no-decompression time indicated in Table 1:
NST – RNT = ABT (for diving with a safety stop)
If, however, a repetitive dive requires a decompression stop, the total dive time will be the sum of the actual dive time and the residual nitrogen time:
AVT + RNT = TWT (for a decompression dive)
Air travel after dives
Before an upcoming air travel after the last dive, a certain time interval must be maintained. This is due to the fact that during the flight the absolute pressure in the cabin is maintained below atmospheric pressure, approximately equal to the pressure at 2000 meters above sea level.
The difference in partial pressures of residual nitrogen and absolute atmospheric pressure increases significantly, which can lead to decompression sickness.
The values of the required pre-flight intervals are listed in the right column marked “airplane” in Table 2.
The same interval is recommended for those who are going to ascend to 2000 meters above sea level after diving.