Before high-altitude diving, the instrument must be set to the Altitude Adjustment mode
to adjust the calculations for the new altitude. The maximum partial pressures of nitro-
gen allowed by the mathematical model of the dive computer are reduced according
to the lower ambient pressure.
As a result, the allowed no-decompression-stop limits are considerably reduced.
10.3. Oxygen exposure
The oxygen exposure calculations are based on currently accepted exposure time
limit tables and principles. In addition to this, the dive computer uses several methods
to conservatively estimate the oxygen exposure. For example:
•
The displayed oxygen exposure calculations are raised to the next higher percent-
age value.
•
The CNS % limits up to1.4 bar are based on 1991 NOAA Diving Manual limits
•
The OTU monitoring is based on the long-term daily tolerance level and the recovery
rate is reduced.
•
for recreational scuba diving, the recommended upper limit of 1.4 bar PO2 is used
as a default
Oxygen related information displayed by the dive computer is also designed to ensure
that all warnings and displays occur at the appropriate phases of a dive. For example,
the following information will be shown before and during a dive when the computer
is set in mode:
•
The selected O
2
% on the alternative display
•
OLF% alternative display for either CNS% or OTU% (whichever is larger)
•
Audible alarms are given and the OLF value starts to blink when the 80% and
100% limits are exceeded.
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