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> ...
> my understanding was (and most likely always will
> be) that you either have a decompression ceiling
> or not.
Virtualy you have a ceiling on every dive, even on
NDL-dives! In NDL-dives your decompression is done by
ascent speed and limited by the decomodel (most likely
10 meters/minute). And because this value will vary
during ascend it makes sense to add an additional
ceilings like minimum deco or safety stop...
