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jheimann%scsd.dnet@gt*.co*
> 
> I accidently sent my message before I was done typing.
> 
>A lot of people here use the DCIEM tables for technical dives.  These are very
>conservative, are designed for cold water diving [...]
>and are considered to be among the best tested tables.  Statistically they
>have much lower risk than either the Navy or BSAC tables.

I would be very, very careful about any blanket statements about this
kind of thing.  It turns out that the DCIEM tables are not uniformly
safer than either the RN or USN tables, and that none of these 3
tables are "safe enough" for a large number of profiles.

Deep, short dives like the ones mentioned recently (160'/50m for
30min, for example) are relatively safe no matter which table you use.
Often the DCIEM tables require much longer stops than the Navy tables
for no appreciable gain in safety.

Safety is not simple!

>Many people feel that the Navy tables are reasonably safe if O2 is used for 
>10 and 20 fsw stops.  Randy Bohrer, a US trimix instructor and table authority
>has told me that, for practical purposes, one can assume that one minute on 
>O2 is worth two on air for these stops.

Sorry to be such a pisser, but this too is a dangerous notion to be
bandying about.  There have been reported cases of DCI in which the
victim was IMPROPERLY decompressing on oxygen, because he was told
that "one on O2 counts for two on air."  This seriously compromised
the decompression schedule he should have been performing, and
probably was the direct cause of his serious DCI.

>As Bill Mayne points out, repetitive diving is where the Haldanian model tends
>to fall apart.  

Now this, I can agree with!

> [...] most divers who have paid $50-$100 and spent several hours being
> seasick on the way to the wreck want to get as much bottom time
> as possible, risk be damned.

This is interesting.  A while back on rec.scuba folks were asking what
"experienced diver" meant.  The divers who meet this description would
not meet my description of "experienced."  Judging by decisions I've
made similar to the one above, I don't consider myself "experienced."

David Story                        NAUI AI Z9588, PADI DM 43922, EMT
story@be*.wp*.sg*.co*		  Every dive is a decompression dive.

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