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No Decompression Time Remaining (NDC)
NDC is the maximum amount of time that you can stay at your present depth before
entering decompression. It is calculated based on the amount of nitrogen absorbed by
hypothetical tissue compartments. The rates each of the compartments absorb and release
nitrogen is mathematically modeled and compared against a maximum allowable nitrogen
level. Whichever one is closest to this maximum level is the controlling compartment for
that depth. Its' resulting value will be displayed numerically along with the identifying icon
and graphically as the TLBG.
As you ascend from depth following a dive that has approached the no decompression
limit, the TLBG will recede as control shifts to slower compartments.
This is a feature of the decompression model that is the basis for multilevel diving, one
of the most important advantages that Oceanic PDCs offer.
Oxygen Time Remaining (OTR)
Oxygen accumulation (exposure) during a dive, or 24 hour period, appears graphically
as the O2 Bar Graph (O2BG) or numerically as %O2. As time remaining before reach-
ing the oxygen exposure limit decreases, segments are added to the O2BG or %O2
increases.
When OTR becomes less than the NDC, and/or Air Time Remaining, calculations for that
depth will be controlled by oxygen. OTR will then appear as the DTR display.
As oxygen accumulation continues to increase, the O2BG will enter the Caution Zone.
(continued on page 18)
