Operating instructions

1. If a diver had less than two hours total accumulated dive time in the last 48 hours, then a 12 hour surface
interval before flying is recommended.
2. Following any dive that requires a decompression stop, flying should be delayed for at least 24 hours, and if
possible, for 48 hours.
Since the introduction of the 1990 UHMS guidelines, the Divers Alert Network (DAN) has introduced data that
resulted in DAN’s position that:
“A minimum surface interval of 12 hours would be required in order to be reasonably assured a diver will remain
symptom free upon ascent to altitude in a commercial jetliner (altitude up to 8,000 feet). Divers who plan to make
daily, multiple dives for several days, or make dives that require decompression stops, should take special precau-
tions and wait for an extended surface interval beyond 12 hours before flight.”
Both the UHMS and DAN agree that:
“There can never be a flying after diving rule that is guaranteed to prevent decompression sickness completely.
Rather, there can be a guideline that represents the best estimate for a conservative surface interval for the vast
majority of divers. There will always be an occasional diver whose physiological makeup or special diving circum-
stances will result in the bends”
Figure 7
Pre-Dive Planning
Sequence
Pre-Dive Planning Sequence
The last display shown during Surface Mode is the Pre-Dive Planning Sequence
(PDPS). See figure 7. The Pre-Dive Planning Sequence allows you to plan your
next dive by giving you the maximum no-decompression time for various
depths. Since the computer is always monitoring the off-gassing of nitrogen,
the longer you stay on the surface, the more NDT you get. In the PDPS, the
Matrix displays the following information:
a. Dashed no-decompression time icon. The no-decompression time icon
is dashed during the pre-dive planning sequence, as opposed to the solid
line displayed while diving.
b. Depth Scrolling. The PDPS scrolls from 30 ft. to 160 ft. in 10-foot
increments. The metric version scrolls from 9m to 48m in 3-meter incre-
ments.
c. Adjusted no-decompression times. For each depth, the Matrix shows
the maximum allowable no-decompression time. This time increases the
longer you stay on the surface.
d. Dive number. Dive number is the number of the dive just completed.
Before the first dive of the day, this number is 0.
NO-DECOMPRESSION DIVE MODE
When the Matrix goes deeper than five feet, it switches from Surface Mode to No-
Decompression Dive Mode (figure 8). In No-Decompression Dive Mode, the computer
displays the following information:
a. Current Depth. Current depth is displayed to 250 feet (76 m). At depths deeper
than 250 feet (76 m), the depth display is replaced with three dashes. (See
Chapter 3, “Extreme Situations”)
b. No-decompression Time (NDT). NDT is the amount of time you can stay at the
current depth before entering decompression mode. If you stayed at a constant
depth, the NDT would countdown to zero. As you ascend to shallower depths, the
computer credits you with more NDT.
c. Maximum Depth. Maximum depth is the deepest depth reached during the dive. It
only appears when you ascend 3 feet (1 m) shallower than the deepest depth
reached during the dive. For example, if you made a dive to 100 feet (30 m), the
max depth display would not appear until you ascended to 97 feet (29 m).
d. Bottom Time. Bottom time is the total amount of time spent underwater. The
bottom timer begins when you descend below five feet and stops when you ascend
above 3 feet.
Figure 8
No-decompression Dive
Mode