42
Figure 15: How the IQ-600 measures Actual Bottom Time
and Surface Interval Time.
However, as Figure 15 shows, if you spend less than ten min-
utes at the surface, or above a depth of 5 ft/1.5m, then descend
again, the IQ-600 will count both descents—and the surface
interval between them—as part of the same dive.
2.08 Understanding FO
2
Default
Throughout its descriptions of Dive Plan and Dive Modes, this
manual makes several references to what may happen if the
IQ-600’s FO
2
setting “defaults.” In this section we will explain
why, when and how this occurs, and how it may impact you as
an IQ-600 user.
In your entry-level Enriched Air Nitrox Diver training,
you learned that among the greatest risks Nitrox (EANx) use
poses is that of CNS Oxygen Toxicity. One way CNS Oxygen
Toxicity can occur is when divers breathe Nitrox at depths
where the partial pressure of oxygen (PO
2
) exceeds safe limits.
