Diving With Galileo; Nitrox; Alarms - SCUBAPRO UWATEC Galileo Luna Manual Del Usuario

3. diving with Galileo

3. diVinG WitH GaLiLeo
3.1

Nitrox

Nitrox is the term used to describe breathing
gases made of oxygen-nitrogen mixes with
oxygen percentage higher than 21% (air).
Because Nitrox contains less nitrogen
than air, there is less nitrogen loading on
the diver's body at the same depth as
compared to breathing air.
However, the
concentration in Nitrox implies an increase
in oxygen partial pressure in the breathing
mix at the same depth. At higher than
atmospheric partial pressures, oxygen can
have toxic effects on the human body. These
can be lumped into two categories:
- Sudden effects due to oxygen partial
pressure over 1.4bar. These are not
related to the length of the exposure to
high partial pressure oxygen, and can
vary in terms of the exact level of partial
pressure they happen at. It is commonly
accepted that partial pressures up to
1.4bar are tolerable, and several training
agencies advocate maximum oxygen
partial pressures up to 1.6bar.
- Long-exposure effects to oxygen
partial pressures over 0.5bar due to
repeated and/or long dives. These can
affect the central nervous System,
cause damage to lungs or to other vital
organs.
Galileo keeps you safe with respect to these
two effects in the following ways:
1) Against sudden effects: Galileo has
an MOD alarm set for a user-defined
ppO max. As you enter the oxygen
2
concentration for the dive, Galileo
shows you the corresponding MOD
for the defined ppO
value of ppO
1.4bar. This can be adjusted to your
preference between 1.2 and 1.6bar. It
can also be turned off. Please refer to
section 2.3.4 for more information on
how to change this setting.
2) Against long exposure effects: Galileo
"tracks" the exposure by means of the
40
increase in oxygen
max. The default
2
max from the factory is
2
CNS O clock. At levels of 100% and
2
higher there is risk of long-exposure
effects, and consequently Galileo will
activate an alarm when this level of
CNS O is reached. Galileo can also
2
warn you when the CNS O
reaches 75% (see section 2.6.2). Note
that the CNS O clock is independent
2
of the value of ppO
user.
The CNS O clock increases when the
2
oxygen partial pressure is higher than
0.5bar, and decreases when the oxygen
partial pressure is lower than 0.5bar. Hence,
while on the surface breathing air you will
always be decreasing the CNS O
During the dive, the depth at which 0.5bar
is reached for various mixes is as follows:
Air:
32%:
36%:
depth
at which ppO
2
reaches 0.5bar for
three commonly
used mixes
decreases
21% 13m (43ft)
32% 6m (20ft)
36% 4m (13ft)
3.2

Alarms

Galileo can alert you of potentially dangerous
situations via warnings and alarms.
Warnings represent situations that require
the diver's attention, but ignoring them
does not represent an immediate risk. The
detailed description of each warning and
how it appears on the screen is presented
in section 2.6.
Alarms, on the other hand, can not be
turned off because they represent situations
level
2
max set by the
2
clock.
2
13m/43ft
6m/20ft
4m/13ft
ppo
2
0.21bar
CNS O %
2
0.5bar
CNS O %
2
increases