The Unlimited/No-Decompression Table (Table 9-6) serves three purposes. First,
the table identifies that on a dive with the depth 20 fsw and shallower, unlimited
bottom time may be achieved. Second, it summarizes all the depth and bottom
time combinations for which no decompression is required. Third, it provides the
repetitive group designation for each unlimited/no-decompression dive. Even
though decompression is not required, there is still an amount of nitrogen
remaining in the diver’s tissues for up to 12 hours following a dive. If they dive
again within a 12-hour period, divers must consider this residual nitrogen when
calculating decompression from the repetitive dive. Any dive deeper than 25 fsw
that has a bottom time greater than the no-decompression limit given in this table
is a decompression dive and must be conducted per the Standard Air Decompression
Table.
Each depth listed in the Unlimited/No-Decompression Table has a corresponding
no-decompression limit listed in minutes. This limit is the maximum bottom time
that divers may spend at that depth without requiring decompression. Use the
columns to the right of the no-decompression limits column to obtain the repetitive
group designation. This designation must be assigned to a diver subsequent to
every dive.
To find the repetitive group designation:
1. Enter the table at the depth equal to, or next greater than, the maximum depth
of the dive.
2. Follow that row to the right to the bottom time equal to, or just greater than,
the actual bottom time of the dive.
3. Follow the column up to the repetitive group designation.
TABLE 9-6 Unlimited/No-Decompression Limits and Repetitive Group Designation Table for Unlimited/No-
Decompression Air Dives.
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In planning a dive, the Dive Supervisor wants the divers to conduct a
brief inspection of the work site, located at a depth of 152 fsw. Determine the
maximum no-decompression limit and repetitive group designation.
The maximum bottom time that may be used without requiring decompression
and the repetitive group designation after the dive can be found in either
the Unlimited/No-Decompression Table or the Standard Air Decompression
Table.
Using the Unlimited/No-Decompression Table.
1. Locate the dive depth in the Depth column. Because there is no entry for
154 (152 +2) fsw, round the depth up to the next greater depth of 160 fsw.
2. Move vertically across the table to locate the no-decompression limit in
the Unlimted/No-Decompression Limits column. The no-decompression
limit is 5 minutes. To avoid having to make decompression stops, the
divers must descend to 152 fsw, make the inspection and begin ascent
within 5 minutes of leaving the surface.
3. To find the repetitive group designation, follow the 160-fsw entry to the
right to the 5-minute bottom time entry and then follow it vertically to the
top of the column. This shows the repetitive group designation to be D.
Using the Standard Air Decompression Table.
1. Locate the schedule for the dive depth. Because there is no schedule for
154 (152 +2) fsw, round the depth up to the next greater depth of 160 fsw.
2. Follow the 5-minute bottom time row all the way horizontally to the right.
There is a “0” listed in the decompression stops column and D is depicted
in the Repetitive Group column.
Figure 9-5 is a diving chart for this dive.
FIGURE 9-5 Completed Air Diving Chart.
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