46
Be aware, however, that the computer’s ability to accurately
track your exposure to elevated partial pressures of oxygen is
now shot for the next 24 hours.
Another situation worth addressing would be one typically
encountered by dive instructors conducting open-water train-
ing. Such training involves numerous back-to-back ascents and
descents, with little opportunity to set FO
2
in between. Under
such circumstances, users may choose to set their IQ-600s to
air, thus eliminating the possibility that the computer will
default between dives. In so doing, however, it is important to
understand that—if breathing a gas mixture other than air—the
computer is no longer able to accurately track users’ exposure
to elevated partial pressures of oxygen. This becomes some-
thing users will have to do so on their own.
Similarly, some divers may choose on occasion to set
their IQ-600s to air, or to an FO
2
less than that of the gas mix-
ture they are actually breathing, in a effort gain a safety mar-
gin in respect to the risk of DCI. Again, it is critical to bear in
mind that doing so robs the IQ-600 of the ability to accurately
track your exposure to elevated partial pressures of oxygen,
and that the O
2
exposure information it displays will no longer
be accurate.
All of the possibilities discussed here point out the need for
one further word of caution. You should not rely on your IQ-
600 as the sole means of tracking your exposure to elevated
partial pressures of oxygen (PO
2
s). Use either a second Nitrox-
capable computer, or the tracking methods you learned as part
of your entry-level Nitrox Diver training, to confirm that the
oxygen-exposure information the IQ-600 provides in fact
accurately reflects your overall O
2
exposure status.
