95
No Decompression Dive Time Remaining (NDC)
No Decompression Dive Time Remaining is the maximum
amount of time that you can stay at your present Depth before
entering a Decompression situation. It is calculated based on
the amount of Nitrogen absorbed by hypothetical tissue compart-
ments. The rates each of these 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 symbols TIME and NDC (Fig. 79a) and graphi-
cally as the Tissue Loading Bar Graph (Fig. 79b).
As you ascend from Depth following a dive that has approached
the No Decompression Limit, the Nitrogen Bar Graph segments
will recede as control shifts to slower compartments. This is a
feature of the Decompression Model that is the basis for Multi-
level Diving, one of the most important advantages that Oceanic
dive computers offer.
The ATOM's algorithm is based upon Haldanes theory using
maximum allowable nitrogen levels developed by Merrill Spen-
cer. Repetitive diving control is based upon experiments de-
signed and conducted by Dr. Ray Rogers and Dr. Michael
Powell in 1987. Diving Science and Technology
®
(DSAT), a
corporate affiliate of PADI
®
, commissioned these experiments.
Fig. 79 - NO DECO DTR
b
a
