User manual

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CHROMIS USER MANUAL
4.7.5.2 Altitude and the decompression algorithm
Atmospheric pressure is a function of altitude and weather conditions. This is an important
aspect to consider for diving, because the surrounding atmospheric pressure has an
infl uence on on-gassing and off-gassing of nitrogen in your body.
Chromis divides the possible altitude range in 5 classes that are illustrated on the
picture below:
The altitude classes are defi ned in terms of
approximate elevations because the effect
of weather conditions can make the switch
point pressure occur at different levels.
WARNING
At altitude class 4 Chromis functions in gauge mode
only (automatic switch from computer mode).

NOTE: You can check your current
altitude class and elevation by
activating the altitude meter. Refer to
chapter Checking the Altitude on
how to do so.

NOTE: Chromis deals with
altitude automatically: it monitors
the atmospheric pressure every
60 seconds and if it detects a
suffi cient drop in pressure, it does
the following: it indicates the new
altitude range and, if applicable,
the prohibited altitude range;
it indicates the desaturation time,
which in this case is an adaptation
time to the new ambient pressure. If
a dive is started during this adaptation
time, Chromis considers it as a
repetitive dive, since the body has
residual nitrogen.
4.7.5.3 Prohibited altitude
Going to altitude, as well as fl ying after
diving, exposes your body to a reduced
ambient pressure. In a way similar to the
no-fl y time, Chromis advises you which
altitude classes are safe to reach after a
dive and which aren’t. If you have to drive
over a mountain pass to return home after
a dive, you can view this information in the
planner menu.
The current altitude class is shown on the left
of the middle row and the prohibited altitude is
shown on the right. On the example above, the
diver is presently at altitude class 2 and should
not reach altitudes above 3000m (class 3).
By increasing the interval time at the top
row the allowed altitude increases due to
the desaturation caused by the time spent
at the current altitude class.