1.3 Nitrox information (O
2
-information)
For dives with compressed air in normal recreational diving, nitrogen is the decisive gas for the decom-
pression calculations. When diving with nitrox, the toxicity of oxygen rises with the increase of the fraction
of oxygen and increasing depth and can limit dive time and the maximum depth. Smart includes this in the
calculations and displays the necessary information:
<O
2
% MIX>
Fraction of oxygen: The fraction of oxygen in the Nitrox mixture can be set bet-
ween 21% (normal compressed air) and 100%. Your selected mix will be the
basis for all calculations.
ppO
2
max
Maximum allowable partial pressure of oxygen: The higher the percentage of
oxygen in the used mixture, the shallower the dive depth at which the tolera-
ble partial pressure of oxygen (ppO
2
max) is reached. Default setting is a limit
of 1.4 bar, it can be changed with the SmartTrak software in the range of 1.2
to 1.95 bar. The Smart does not display the entered ppO
2
limit, but warns the
diver acoustically and optically if he reaches the depth at which the ppO
2
limit
is reached.
The CNS O
2
%-value/alarm is not influenced by the selected ppO
2
max.-setting.
<CNS O
2
LIMIT>
Oxygen toxicity: With the increased
percentage of oxygen, the oxygen in
the tissues, especially in the central
nervous system (CNS) becomes
important. If the partial pressure of
oxygen rises above 0.5 bar, the CNS
O
2
value increases, if the partial pres-
sure of oxygen is below 0.5 bar, the
CNS O
2
value decreases. The closer
the CNS O
2
value comes to 100%,
the closer the limit, where symptoms
can occur. See page 17.
Nitrox diving may only be attempted by experienced divers after proper training
from an internationally recognized agency.
12
1 Terminology / Symbols
III Uwatec
®
Smart dive computers
CNS O
2
%
increases
ppO
2
0,5 bar
CNS O
2
%
decreases
0,21 bar
WARNING
Eg-SMART III+IV 13.10.2001 11:15 Uhr Seite 12
