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1)non issue
2)Bottom time starts when you hit the bottom and ends when you leave the
bottom PERIOD
3)If you are stressing on a fast descent, then you should not make ANY
descent,all of these are non issues when you dive with other competent
divers
This is all pablum-EZ
>There are several reasons why you may want limit the descent rate:
>
>1) HPNS: For the normal mortal this is a no issue. As far as I recall
>the first symptoms of HPNS can occour at ~280ft while diving Helium-
>Oyxgen and exceeding 100fpm. Small amounts of nitrogen largely delay
>this effect to even deeper dives (>400ft). For hyperoxic trimix this
>is certainly not the limit.
>
>2) Tables: If you _plan_ your dive with a descent rate of 30fpm and
>you descent faster you will indeed exceed the table. Example: for
>a 300ft dive with 15min real bottom time your table would tell you
>a decompression schedule that starts 25 min after begin. If you
>descent with 60fpm you hit the gound 5 mins earlier, hence when you
>stick to your table and leave the bottom at 25mins you already made
>20 min. real bottom time (=you are more saturated than planned).
>The solution to this problem is either to stick to the table (ie.
>don't be faster than recommended) or get tables for the descent rate
>you use. If you use a computer program selecting faster the descent
>rates will make the schedule more conservative. For my private tables
>I calculate the schedules based on a 60fpm descent rate.
>
>For the depth where hyperoxic trimix makes sense (<200ft) the
>differences in the decompression schedule between a 30fpm and
>a 100fpm should be very small.
>
>3) Stress: This is the real reason to reduce your descent rate. If
>you descent slower:
> * bouyancy control is easier and more precise
> * equalization is easier
> * you have time to look for your buddies and your equipment
> * you reach the bottom much more relaxed
>For my taste a descent rate of 45-35fpm is just fine.
>
>Greetings,
>Frank Riffel
>
>Jbdvr@ao*.co* wrote:
>
>> Hi, the current issue of Advanced Diver Magazine has a article called
Oxygen
>> Enriched Trimix, which deals with mixes with a 02 of 21 to 28%. The
article
>> states that the descent rate should be 30fpm, and that ''The danger in
>> descending too fast is that the inert gas uptake may exceed what is
planned
>> for the schedule, which can increase your risk of DCI''. Question: What
is
>> the current conventional wisdom on proper descent rates for trimixes?
>> thanks.......Joe Boone
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