CHAPTER 14 Surface Supplied Mixed Gas Diving Procedures
Change A 14-7
The interval from leaving 40 fsw in the water to arriving at 50 fsw in the
chamber cannot exceed 5 minutes.
In the chamber, have the divers breathe oxygen for 30 minute periods sepa-
rated by 5-minute air breaks. The number of oxygen periods required is
indicated in Table 14-3. The first period consists of 15 minutes on oxygen at
50 fsw followed by 15 minutes on oxygen at 40 fsw. Periods 2, 3, and 4 are
spent at 40 fsw. Periods 5, 6, 7 and 8 are spent at 30 fsw. Ascent from 50 to 40
and from 40 to 30 fsw is at 30 fsw/min. Ascent time is included in the oxygen/
air time. Ascent from 40 to 30 fsw, if required, should take place during the air
When the last oxygen breathing period has been completed, return the diver to
breathing chamber air.
Ascend to the surface at a rate of 30 fsw/min.
Variation in Rate of Ascent. The rate of ascent to the first stop and between
subsequent stops is 30 fsw/minute. Minor variations in the rate of travel between
20 and 40 fsw/minute are acceptable.
Early arrival at the first stop: If the divers arrive early at the first stop:
Begin timing the first stop when the required travel time has been completed
If the first stop requires a gas shift, initiate the gas shift and ventilation upon
arrival at the stop, but begin the stop time only when the required travel time
has been completed.
Delays in Arriving at the First Stop.
Delay less than 1 minute. Delays in arrival at the first stop of less than 1
minute may be ignored.
For delays in excess of 1 minute:
Round up the delay to the next whole minute.
Add the rounded up delay time to the bottom time.
Recalculate the required decompression.
If no change in schedule is required, continue on the planned decom-
If a change in schedule is required and the new schedule calls for a de-
compression stop or stops deeper than the diver's current depth, per-
form any missed deeper stops at the diver's current depth. Do not go