5.7. Algorithm settings
Suunto's decompression model development originates from the 1980s when Suunto
implemented Bühlmann's model based on M-values in Suunto SME. Since then, research and
development has been ongoing with the help of both external and internal experts.
5.7.1. Bühlmann 16 GF algorithm
The Bühlmann decompression algorithm was developed by Swiss physician Dr. Albert A.
Bühlmann, who researched into decompression theory starting from 1959. The Bühlmann
decompression algorithm is a theoretical mathematical model describing the way in which
inert gases enter and leave the human body as the ambient pressure changes. Several
versions of the Bühlmann algorithm have been developed over the years and adopted by
many dive computer manufacturers. Suunto Ocean is using Suunto’s Bühlmann 16 GF dive
algorithm that is based on the Bühlmann ZHL-16C model that we have implemented our own
code for. The algorithm can be modified by using gradient factors to set the level of
conservatism.
NOTE: Because any decompression model is purely theoretical and does not monitor
the actual body of a diver, no decompression model can guarantee the absence of DCS.
Always take your personal factors, the planned dive, and your dive training into
consideration when choosing the appropriate gradient factors for your dive.
5.7.2. Gradient Factors
Gradient Factor (GF) is a parameter to create various levels of conservatism. GFs are divided
into two separate parameters, Gradient Factor Low and Gradient Factor High.
By using GF with the Bühlmann algorithm, you can set your safety margin for the dive by
adding conservatism to control when
dierent tissue compartments reach their acceptable
M‑value. A Gradient Factor is defined as percentage of the M-value Gradient and defined
from 0% to 100%.
A commonly used combination is GF Low 30% and GF High 70%. (Also written as GF 30/70.)
This setting means that the first stop would take place once the leading tissue reaches 30% of
its M-value. The lower the first number is, the less supersaturation is allowed. As a result, the
first stop is required when you are deeper. A Gradient Factor of 0% represents the ambient
pressure line and a Gradient Factor of 100% represents the M-value line.
In the following illustration, GF Low is set to 30% and the leading tissue compartments react
to the 30% limit of the M-value. At this depth the
first decompression stop takes place.
Suunto Ocean
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