CHAPTER 9 Air Decompression
Change A 9-31
they are only displaying Type I symptoms. Symptoms occurring during the
chamber stops are treated as recurrences (Chapter 21).
Example. A dive is conducted to 123 fsw for 48 minutes using the Surface
Decompression Table Using Air. Determine the correct decompression schedule.
Solution. The correct decompression schedule for a dive conducted to 123 fsw for
48 minutes is the 130/50 schedule. The decompression chart is shown in Figure
Repetitive Dives. If a second surface decompression air dive is planned within a
12-hour period, the same rule applies as for making a second Sur D O2 dive (para-
Example. A repetitive Sur D Air dive is planned for 138 fsw for 20 minutes. The
previous dive was to 167 fsw for 30 minutes. The surface interval was 4 hours 27
minutes. Determine the correct decompression schedules.
Solution. The correct schedule for the first dive is 180/30. The correct schedule
for the second dive is 180/50. As explained in the Sur D O2 procedure, the correct
procedure is to decompress the divers on a schedule for the maximum depth
attained and the total of bottom times of all dives made in the previous 12 hours.
Figure 9-18 illustrate the first dive, the repetitive dive worksheet is shown in
Figure 9-19 and the repetitive dive for the example above is shown in Figure 9-20.
EXCEPTIONAL EXPOSURE DIVES
Exceptional exposure dives are those dives in which the risk of decompression
sickness, oxygen toxicity, and/or exposure to the elements is substantially greater
than on normal working dives. Decompression schedules for exceptional exposure
dives are contained in the Standard Air Decompression Table. These exceptional
exposure schedules are intended to be used only in emergencies, such as diver
entrapment. Exceptional exposure dives should not be planned in advance except
under the most unusual operational circumstances. The Commanding Officer must
carefully assess the need for planned exceptional exposure diving and prior CNO
approval for such diving is required. Selected exceptional exposure dives have
been proven safe in controlled conditions and are authorized at the Naval Diving
and Salvage Training Center during certain phases of diver training.
Surface Decompression Procedures for Exceptional Exposure Dives. The long
decompressions times associated with exceptional exposure dives impose unusual
demands on a divers endurance. There is also limited assurance that the dive will
be completed without decompression sickness. These two risks can be reduced by
using surface decompression techniques rather than completing decompression
entirely in the water.