Deco Terminology - call for discussion

Linus Torvalds torvalds at
Wed Feb 12 12:03:37 UTC 2014

On Wed, Feb 12, 2014 at 10:44 AM, Joe Ross <joe at> wrote:
> I don't know if it's my place to weigh in here, but as of 2014, PADI is
> using the terminology "no stop" dives, since all dives are, in fact,
> decompression dives.

I've seen that "all dives are decompression dives" being repeated a
lot in "newer" literature, and it is, in my opinion, way more
misleading than "no deco" ever was.

Many (most?) recreational dives literally *never* have a ceiling. It's
not that they are "decompression dives without any mandatory stops".
They simply don't involve tissue pressure differentials that are high
enough to matter for human physiology unless you have other issues.

And the fact that you have a tissue pressure differential at all
doesn't just magically make something a "decompression dive".  It
really doesn't.

Put it this way: would you ever say that "all flights are
decompression flights"? No, you wouldn't. A decompression event during
a flight is something very clear, and it does *not* make all other
flights "decompression flights" just because the normal cabin pressure
may be 75% of normal or whatever. Or does anybody talk about
"decompression weather" when the ambient pressure drops? No, they
don't. We don't talk about "decompression elevator rides" either.

I personally think "no deco", "no stops" and "recreational diving" are
all exactly the same thing - and they mean what people *intend* it to
mean.  Language is more like what Humpty Dumpty described in Alice in
Wonderland than people sometimes try to claim. There's no reason to
try to claim that one naming is "more correct" than another.  And I
claim that it is actively *incorrect* and misleading (despite all the
PADI/SDI/whatever course books and videos that do it) to claim that
"all diving is decompression diving".

As far as I can tell, "no deco" is still the common use. And "no
stops" (or, as mentioned, "recreational") would be equally correct,
but I think "no deco" is certainly the common one, and "NDL" in
particular is certainly the normal short-hand for how much time you
have left. I've never heard anybody ever say "no stop time", although
I'm sure the "no stop" people are trying to make it a thing. Has
anybody ever seen "NST/NSL"?

So I would suggest we keep to "no deco" and "NDL" because it's the
common use phrase. Having the alternatives mentioned in
explanations/docs migth be fine, but let's not make it show up in
actual subsurface use.


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