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As discussed earlier, if you ascend above a depth of 5 ft/1.5m,
then descend below this depth within ten minutes, the comput-
er will treat this descent as a continuation of the same time,
made using the same cylinder(s). Thus, the computer will hold
its current FO
2
setting for the continuation of the dive.
On the other hand, if your surface interval (or time spent
above a depth of 5 ft/1.5m) exceeds ten minutes, the IQ-600 will
treat subsequent descents as a separate dive. If the computer was
previously set to an FO
2
of 22 percent or more, it will assume you
may have switched cylinders prior to descending. Thus, to protect
you from the consequences of diving a gas mixture whose FO
2
is
unknown, the IQ-600’s FO
2
setting will default.
There is one more way in which the IQ-600’s FO
2
setting can
default. Let’s say you set the computer’s FO
2
to a value of from
22 to 50 percent, but do not actually go diving. In instances such
as these, the IQ-600 will hold its FO
2
setting until midnight, then
default. This helps protect you in the event you dive the next day
with a cylinder whose oxygen content does not match that of the
cylinder you intended to use the day before.
Dealing With FO
2
Default: As outlined previously, the best
way to deal with FO
2
default is to simply avoid it. Doing so is
easy—simply access Dive Plan Mode prior to every dive and
make sure the FO
2
setting displayed accurately matches that of
your breathing media.
Okay, what happens if you forget to do so? As you should
already know, if the IQ-600’s FO
2
setting is in default, the
computer’s audible alarm will sound as you enter the water
and/or begin your descent. If you hear the alarm, halt any
descent, surface immediately and reset the IQ-600 to the cor-
rect FO
2
. Little harm done.
