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English
PO2 ALLARM.
The computer is able to continuously monitor another fundamental oxygen-related
parameter: Partial Pressure (PO2). Oxygen toxicity, in fact, may be due to excessi-
ve exposure or to maximum PO2 being exceeded, which in actual practice means
that the limit depth permissible with the mix being used has been exceeded. As
discussed above, the limit value of PO2 is set by the diver in a 1.2 bar to 1.6
bar range. GOA/CARTESIO considers 1.6 bar as the maximum admissible limit
for Partial Pressure and, as a function of the mix used, automatically indicates the
maximum depth that can be reached. Do not forget that the oxygen toxicity limit
may be reached even when air is used. This limit varies as a function of the PO2
value set.
GOA/CARTESIO provides for a default value set in the factory of 1.4 bar, which,
in air, corresponds to a maximum depth of 56.6 m (186 ft.). Needless to say,
you can set the computer to other values of PO2, up to a maximum of 1.6 bar:
this can be done only when you are at surface level, from the DIVE-S PPO2 SET
screen.
To warn the scuba diver of excessive PO2 , the computer has a alarm.
When the limit depth corresponding to the PO2 setting (from 1.2 bar to 1.6 bar) is
reached, an audible alarm is given out and at the same time a visual alarm shows
the PO2 icon ashing together with the current depth value. As soon as you acend
to a lesser depth, the audible alarm is silenced, the current depth stops flashing
and the icon also stops flashing, but stays ON during the rest of the dive and
it remains recorded in the LOGBOOK.
CNS TOXICITY DISPLAY
The GOA/CARTESIO computer by Cressi can illustrate through charts the degree
of oxygen toxicity to the Central Nervous System (CNS). The degree of toxicity
depends on Oxygen Partial Pressure and a diver’s exposure time to high values of
Oxygen Partial Pressure (PO2).
The oxygen toxicity level appears on the display as a column made up of 5
segments, which indicate increasing quantities of oxygen build-up. When all the
segments are lit, it means that 100% of the maximum admissible CNS tolerance
has been reached and the scuba diver is in danger of hyperoxia.
Therefore, it is essential to be able to monitor continuously this value, which
depends on Oxygen Partial Pressure and exposure time and should always be
controlled during a dive. When the oxygen level reaches risky levels, close to
maximum admissible toxicity (4 segments lit in 5), the graphic bar begins to ash
and a temporary audible alarm is given out, that tells you are close to CNS toxicity
conditions. If the situation remains the same or gets worse (100% of admissible
toxicity), the bar and the indication keep ashing, and the temporary audible alarm
is repeated until the diver moves up and the oxygen partial pressure decreases to
below 0.6 atmospheres. At this point, the graphic bar stops ashing, but the alarm
is still recorded in the Logbook.
TOXICITY
BAR
NOTE: The result of oxygen exposure computations is rounded up to the next
higher percentage value.
DANGER: Do not use hyper-oxygenated mixes, when diving and espe-
cially in decompression dives, without rst having taken specic trai-
ning courses. The basic Nitrox certification given by the various scuba
diving training centres only enables a diver to use standard hyper oxyge-
nated mixes (Ean32 and Ean 36), within the decompression limits.
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