DCIEM decompression model

Robert Helling helling at atdotde.de
Tue Jul 27 09:01:00 PDT 2021


> On 27. Jul 2021, at 10:32, tormento via subsurface <subsurface at subsurface-divelog.org> wrote:
> Shearwater has introduced DCIEM decompression model on its models.
> Would it be possible to have it in Subsurface to allow pre dive calculation?

as far as I can tell this model is published in terms of tables, for example here


and I read the presse release of Shearwater https://www.shearwater.com/dciem/ as they have a closed collaboration with DCIEM to bring this model into dive computers but I could not find any public documentation of this model.

There is some info here


but nothing on specific model parameters and even more important: nothing about the ascent criterium.

Correct me if I am wrong, but it seems to me the use of the DCIEM tables/model is mainly to fulfil legal requirements for commercial divers, mainly in Canada.

And unless there is an actual documented model to implement, I don’t see much bonus in implementing tables in Subsurface. If you want to plan your dive with a table, you can directly use the table rather than having a program read the table for you (you don’t get additional information).

I don’t know if this is the case for Shearwater, but my guess would be that they treat their interpretation of the model as a trade secret so they have an advantage over their competitors in terms of being the only brand that the above mentioned Canadian commercial diver can use to fulfil her legal duties. Which means, we have no chance in  Subsurface implementing anything that could predict the schedules that their computers compute in DCIEM mode.

But all this is based on a short Google search. If you have any additional information on the model, I would love to learn about it.

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