User manual

32
ALADIN SQUARE USER MANUAL

NOTE: After a desaturation reset the
change between the modes: Gauge,
Apnea and Scuba are possible
immediately. However, since the
gauge and apnea modes are not
tracking your tissue nitrogen loading,
it is recommended to keep the initial
intervals between changes on modes.
WARNING:
Diving after having reset the desaturation
is extremely dangerous and is very likely to
cause serious injury or death. Do not reset the
desaturation unless you have a valid reason to
do so.

NOTE: Removing and replacing the
battery will not reset the desaturation.
Square stores tissue saturation
information in non-volatile memory. For
the time during which the computer
is without battery, the desaturation
calculation is frozen and resumes from
where it had left off as soon as a new
battery is installed.
2.5 Diving with nitrox or with
another decompression gas
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 increase in oxygen
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. Long exposures can
be divided to more severe Central Nervous
System effects and less dangerous long
term Pulmonary Toxicity effects.
Square treats high ppO
2
and long exposure
effects in the following ways:
Against sudden effects: Square has an MOD
alarm set for a user-defi ned ppO
2
max. As
you enter the oxygen concentration for the
dive, Square shows you the corresponding
MOD for the defi ned ppO
2
max. The
default value of ppO
2
max from the factory
is 1.4bar. This can be adjusted to your
preference between 1.0 and 1.6bar. It can
also be turned OFF. Please refer to chapter
Gas settings for more information on how
to change this setting.
Against long exposure effects: Square
“tracks” the exposure by means of the
CNS O
2
clock. At levels of 100% and higher
there is risk of long exposure effects, and
consequently Square will activate an alarm
when this level of CNS O
2
is reached.
Square can also warn you when the CNS O
2
level reaches 75% (see section CNS alarm).
Note that the CNS O
2
clock is independent
of the value of ppO
2
max set by the user.
The CNS O
2
clock increases when the
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
2
clock. During the
dive, the depth at which 0.5bar is reached
for various mixes is as follows:
Air: 13m/43ft
32%: 6m/20ft
36%: 4m/13ft

NOTE: The O
2
concentration of gas
d can only be set to a value higher
than the O
2
concentration for gas 1.
Square requires that the MODs of gas
1 and gas d be at least 3m/10ft apart.
Setting the ppO
2
max value to OFF applies
to gas 1 only. Gas d is always limited to