9-14 Change A
U.S. Navy Diving ManualVolume 2
Solution. Select the equal or next deeper depth and the equal or next longer
bottom time (140 + 2 = 142 fsw). This would be the 150/40 schedule, repetitive
group designator N (see Figure 9-6).
During the 12-hour period after an air dive, the quantity of residual nitrogen in
divers bodies will gradually be reduced to its normal level. If the divers are to
make a second dive within this period (repetitive dive), they must consider their
residual nitrogen level when planning for the dive.
The procedures for conducting a repetitive dive are summarized in Figure 9-7.
Upon completing the first dive, the divers are assigned a repetitive group designa-
tion from either the Standard Air Decompression Table or the Unlimited/No-
Decompression Table. This designation relates directly to the residual nitrogen
level upon surfacing. As nitrogen passes out of the divers tissues and blood, their
repetitive group designation changes. By using the Residual Nitrogen Timetable
(Table 9-7), this designation may be determined at any time during the surface
To determine the decompression schedule for a repetitive dive using either the
unlimited/no-decompression, standard air, or surface decompression table:
Determine the residual nitrogen level just prior to leaving the surface of the of
the repetitive dive (based on the repetitive dive depth), using the Residual
Nitrogen Timetable. This level is expressed as residual nitrogen time, in
Add this time to the actual bottom time of the repetitive dive to get the Equiv-
alent Single Dive Time (ESDT).
Conduct decompression from the repetitive dive using the max depth (MD)
and the equivalent single dive time to select the appropriate decompression
schedule. Avoid equivalent single dives requiring the use of Exceptional
Exposure decompression schedules.
Always use a systematic Repetitive Dive Worksheet, shown in Figure 9-8, when
determining the decompression schedule for a repetitive dive.
Residual Nitrogen Timetable for Repetitive Air Dives. The quantity of residual
nitrogen in a divers body immediately after a dive is expressed by the repetitive
group designation assigned from either the Standard Air Decompression Schedule
or the Unlimited/No-Decompression Table. The upper portion of the Residual
Nitrogen Timetable is composed of various intervals between 10 minutes and 12
hours. These are expressed in hours and minutes (2:21 = 2 hours, 21 minutes).
Each interval has a minimum time (top limit) and a maximum time (bottom limit).