CHAPTER 9 Air Decompression
Travel Rate Exceeded. On a Standard Air Dive, if the rate of ascent is greater
than 30 fpm, STOP THE ASCENT, allow the watches to catch up, and then
continue ascent. If the stop is arrived at early, start the stop time after the watches
UNLIMITED/NO-DECOMPRESSION LIMITS AND REPETITIVE GROUP
DESIGNATION TABLE FOR UNLIMITED/NO-DECOMPRESSION AIR DIVES
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 divers 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 Decompres-
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 repeti-
tive group designation. This designation must be assigned to a diver subsequent to
To find the repetitive group designation:
Enter the table at the depth equal to, or next greater than, the maximum depth
of the dive.
Follow that row to the right to the bottom time equal to, or just greater than,
the actual bottom time of the dive.
Follow the column up to the repetitive group designation.
Example. 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.
Solution. The maximum bottom time that may be used without requiring decom-
pression and the repetitive group designation after the dive can be found in either
the Unlimited/No-Decompression Table or the Standard Air Decompression
Using the Unlimited/No-Decompression Table.