9-44 Change A
U.S. Navy Diving ManualVolume 2
pression benefit for the diver on oxygen. For surface decompression on
air, stops must be adjusted. (See the example below and Figure 9-22.)
Line 13. Record the Repetitive Group Designator at the end of the dive.
Follow all decompression table procedures for ascent and descent
Example: Five hours after arriving at an altitude of 7750 feet, divers make a 60
min air dive to a gauge depth of 75 fsw. Depth is measured with a pneumofathom-
eter having a non-adjustable gauge with a fixed reference pressure of one
atmosphere. The Surface Decompression Table Using Oxygen will be used for
decompression. What is the proper decompression schedule?
The altitude is first rounded up to 8000 feet. A depth correction of +8 fsw must be
added to the maximum depth recorded on the fixed reference gauge. A pneumo-
fathometer correction factor of + 1 fsw must also be added. The divers' actual
depth is 84 fsw. Table 9-3 is entered at an actual depth of 85 fsw. The Sea Level
Equivalent Depth for 8000 feet of altitude is 120 fsw. The repetitive group upon
arrival at altitude is Group F. This decays to Group B during the five hours at alti-
tude pre-dive. The residual nitrogen time for Group B at 120 fsw is 6 minutes.
The Equivalent Single Dive Time therefore is 66 minutes. The appropriate decom-
pression schedule from the Surface Decompression Table Using Oxygen is 120
fsw for 70 minutes. By the schedule, a 4-minute stop at 30 fsw in the water and a
39-minute stop at 40 fsw in the chamber are required. The water stop is taken at a
depth of 22 fsw. The chamber stop is taken at a depth of 40 fsw.
Figure 9-22 shows the filled-out Diving at Altitude Worksheet for this dive.
Figure 9-23 shows the filled-out Diving Chart.
Repetitive Dives. Repetitive dives may be conducted at altitude. The procedure
is identical to that a sea level, with the exception that the sea level equivalent dive
depth is always used to replace the actual dive depth. Figure 9-24 (on page 9-48)
is a Repetitive Dive at Altitude Worksheet.
Example: Fourteen hours after ascending to an altitude of 7750 feet, divers make
a 82 fsw 60 min MK 21 dive using the Standard Air Table. Depth is measured
with a pneumofathometer having a depth gauge adjustable for altitude. After two
hours and 10 min on the surface, they make a second dive to 79 fsw for 30 min and
decompress on the Surface Decompression Table Using Oxygen. What is the
proper decompression schedule for the second dive?
The altitude is first rounded up to 8000 feet. For the first dive, a depth correction
of +1 fsw must be added to the 82 fsw pneumofathometer reading. The divers
actual depth on the first dive is 83 fsw. Table 9-3 is entered at an actual depth of
85 fsw. The Sea Level Equivalent Depth for the first dive is 120 fsw. The repeti-
tive group designation upon completion of the 60 min dive is Group O. This
decays to Group H during the 2 hour 10 min surface interval.
The actual depth of the second dive is 80 fsw (79 fsw plus a 1 fsw pneumofathom-
eter correction). Table 9-3 is entered at an actual depth of 80 fsw. The Sea Level