CHAPTER 9 Air Decompression
Change A 9-23
Once the divers are on the surface, the tenders have three and a half (:03:30)
minutes to remove the breathing apparatus and diving dress and assist the divers
into the recompression chamber.
Pressurizing the recompression chamber with air to 40 fsw should take approxi-
mately 30 seconds (descent rate not to exceed 80 fpm). The total elapsed time
from when the divers leave the 30 foot stop (or 30 fsw if no water stops are
required) to when they reach the 40 foot recompression chamber stop must not
exceed 5 minutes. During descent in the recompression chamber, if a diver cannot
clear and the chamber is at a depth of at least 20 fsw, stop, then breathe oxygen at
20 fsw for twice the 40 fsw chamber stop time. Ascend to 10 fsw and breathe
oxygen again for twice the 40 fsw chamber stop time. Then ascend to the surface.
This safe way out procedure is not intended to be used in place of normal Sur D
If the prescribed surface interval is exceeded and the divers are asymptomatic,
treat them as if they have Type I decompression sickness (Treatment Table 5,
Chapter 21). If the divers are symptomatic, they are treated as if they have Type II
decompression sickness (Treatment Table 6, Chapter 21), even if they are only
displaying Type I symptoms. Symptoms occurring during the chamber stops are
treated as recurrences (Chapter 21).
Upon arrival at 40 fsw in the recompression chamber, the divers are placed on the
Built-in Breathing System (BIBS) mask breathing pure oxygen. The mask should
be strapped on both divers to ensure a good oxygen seal. The designated 40 foot
stop time commences once the divers are breathing oxygen. The divers breathe
oxygen throughout the 40 foot stop, interrupting oxygen breathing after each 30
minutes with a 5 minute period of breathing chamber air (referred to as an air
break). Count the air breaks as dead time and not part of the oxygen stop time.
If the air break interval falls on time to travel, remove oxygen and commence trav-
eling to the surface at 30 fpm. This procedure simplifies time keeping and should
be used whenever using the Surface Decompression Table Using Oxygen.
Remove the O2 mask prior to leaving the 40 fsw stop for the surface.
Example. A dive is planned to approximately 160 fsw for 40 minutes. The dive is
to be conducted using Sur D O2 procedures. Figure 9-12 shows this dive profile.
In the event of oxygen system failure, it is important to be familiar with the appro-
priate air decompression schedules. If the oxygen system fails while the divers are
in the water, the divers are shifted to the Standard Air Decompression Table or the
Surface Decompression Table Using Air. During the chamber phase, use the
procedures listed below in the event of oxygen system failure or CNS oxygen
Loss of Oxygen Supply in the Chamber (40 fsw Chamber Stop). If the oxygen
supply in the chamber is lost at the 40 fsw chamber stop, have the diver breathe
Temporary Loss. Return the diver to oxygen breathing. Consider any time on
air as dead time.