CHAPTER 9 Air Decompression
Change A 9-27
oxygen is planned within a 12-hour period, select the appropriate decompression
Adding the bottom times of all dives made in the previous 12 hours to get an
adjusted bottom time, and
Using the maximum depth obtained in the previous 12 hours.
The equivalent single dive shall not exceed 170/40 for Sur D O2 or 190/60 for
Sur D Air.
Example. A dive is conducted to 165 fsw for 25 minutes, followed by a surface
interval of 3 hours 42 minutes, and a repetitive dive to 133 fsw for 15 minutes. The
Surface Decompression Table Using Oxygen is used for both dives. Determine the
correct decompression schedules.
Solution. The correct decompression schedule is 170/25 for the first dive and
170/40 for the second dive. Even though the second dive was to a maximum depth
of 138 fsw for 15 minutes, the divers must be decompressed for the maximum
depth attained in the previous 12 hours, which was 170 fsw, and a total of all
bottom times, which was 40 minutes. Figure 9-14, Figure 9-15, and Figure 9-16
chart this example.
Even if the second dive is to be a Standard Air dive, combine all bottom times in
the previous 12 hours to get an adjusted bottom time and decompression schedule
from the maximum depth attained in the previous 12 hours.
Surface Decompression Table Using Air. The Surface Decompression Table
Using Air (referred to as Sur D Air) should be used for surface decompression
following an air dive when a recompression chamber without an oxygen breathing
system is all that is available.
The total ascent times of the Surface Decompression Table Using Air exceed
those of the Standard Air Decompression Table; the only advantages surface
decompression using air are getting the divers out of the water sooner and main-
taining the divers in a controlled, closely observed environment during
When using the Sur D Air table, all ascents are made at 30 fpm. This includes the
ascent rate from the last water stop. The time spent on the surface should not
exceed 3½ minutes and the rate of descent to the first recompression chamber stop
should not exceed 60 fpm. The total elapsed time for these three procedures must
not exceed 5 minutes.
If the prescribed surface interval is exceeded and the divers are asymptomatic,
they are treated as if they had Type I Decompression Sickness (Treatment Table 5
or 1A, Chapter 21). If the divers are symptomatic, they are treated as if they had
Type II Decompression Sickness (Treatment Table 6 or 2A, Chapter 21), even if