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 risk of oxygen toxicity rises with the increase of the
fraction of oxygen and the increase of depth and can limit dive time and the maximum depth. Smart Z
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
between 21% (normal compressed air) and 100% in 1% increments. Your
selected mix will be the basis for all calculations.
ppO
2 max.
Maximum allowed partial pressure of oxygen: the higher the fraction of oxy-
gen in the mixture, the shallower the dive depth at which this value of the
partial pressure of oxygen is reached. The depth at which ppO
2
max. is reached
is called Maximum Operating Depth (MOD). Default setting is 1.4 bar, but it can
be set by means of SmartTRAK between 1.0 and 1.95 bar. When you enter the
settings for the gas mixture, Smart Z will display the ppO
2
max. limit setting and
the corresponding MOD. Smart Z warns the diver audibly and visually once the
depth is reached at which the ppO
2
reaches the maximum allowed value.
•
The partial pressure limit set by means of SmartTRAK can be reduced manually
at Smart Z (->18, setting the gas mixture).
• The CNS O
2
% value/alarm is not influenced by the selected ppO
2
max. set-
ting.
"CNS O
2
" Oxygen toxicity: With the increased
percentage of oxygen, the oxygen
in the tissues (especially in the cen
-
tral 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 is to 100%, the
closer the limit where symptoms can
occur. See page 21.
Nitrox diving may only be attempted by experienced divers after proper training
from an internationally recognized agency.
16
1 Terminology / Symbols
UWATEC
®
Smart dive computers
