CHAPTER 15 Saturation Diving
Change A 15-19
UBA Gas. An adequate quantity of gas within an oxygen partial pressure range of
0.441.25 ata shall be available for use.
Emergency Gas. Emergency gas is used as a backup breathing supply in the event
of DDC or PTC atmosphere contamination. An emergency gas with an oxygen
partial pressure of 0.16 to 1.25 ata shall be immediately available to the built-in
breathing system (BIBS). The volume of emergency breathing gas shall be suffi-
cient to supply the divers for the time needed to correct the DDC atmosphere.
Upward excursions of the PTC or DDC or decompression shall not be started
during emergency gas breathing unless the oxygen partial pressure of the divers
inspired gas is 0.42 ata or above.
Example. An emergency gas schedule for a dive to 850 fsw is:
Treatment Gases. . Treatment gases having an oxygen partial pressure range of
1.5 to 2.8 shall be available in the event of decompression sickness. The premixed
gases shown in Table 15-4 may be used over the depth range of 0 1,600 fsw. A
source of treatment gas shall be available as soon as treatment depth is reached.
The source shall be able to supply a sufficient volume of breathing gas to treat
each chamber occupant.
Helium-oxygen gas mixtures conduct heat away from the diver very rapidly. As a
result, temperatures higher than those required in an air environment are necessary
to keep a diver comfortable. As depth increases, the temperature necessary to
achieve comfort may increase to the 8593°F range.
#1 84/16 HeO2
#2 96/4 HeO2
Allowable Depth Range (fsw)
Shift Depth (fsw)
Table 15-4. Treatment Gases.