45
All right, what if you miss or ignore the FO
2
Default Alarm
and dive anyway? As discussed previously, the PO
2
Warning
should sound/appear at a depth of approximately 20 ft/6m. This
should be soon enough for you to surface and correct the problem
without affecting the computer’s Oxygen Limit Index (OLI) too
adversely.
How about a “worst case” scenario? That is, you are well into
a dive when you notice the OLI and PO
2
LIMIT symbol flashing
furiously. (And, did we forget to mention that you are in an over-
head environment, such as a cavern or wreck, that precludes mak-
ing an immediate ascent?) In such situations, common sense must
prevail.
From the understanding gained during your entry-level Nitrox
Diver training, you should know that, unless you have some-
how managed, during the preceding 24 hours, to exceed a
limiting PO
2
of 1.4 atmospheres, or accrue a total of more
than 300 minutes of Actual Bottom Time (ABT), you are
actually well within your overall oxygen limits.
You should also understand that, although the
IQ-600
’s ability
to accurately monitor your exposure to oxygen no longer
exists, it still treats your exposure to nitrogen as though you
were breathing air. Thus, the No-Decompression Limits
(NDLs) or mandatory decompression stop times it reports are,
at worst, no less conservative than they normally would be. If
you are breathing a gas mixture richer in oxygen content than
air, this information may actually be more
conservative than it
normally would be.
What this means is that you can use the IQ-600’s NDL or
mandatory stop information to exit and ascend, and be no less
safe, with respect to the risk of decompression illness (DCI),
than you normally would be.
