Mailing List Archive Mailing List Archive
The real reason to limit your decent rate is to mimimize baratrauma. The rest is patent absurdity. Frank Riffel wrote: > > 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 > -- > Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. > Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'. -- Send mail for the `techdiver' mailing list to `techdiver@aquanaut.com'. Send subscribe/unsubscribe requests to `techdiver-request@aquanaut.com'.
Navigate by Author:
[Previous]
[Next]
[Author Search Index]
Navigate by Subject:
[Previous]
[Next]
[Subject Search Index]
[Send Reply] [Send Message with New Topic]
[Search Selection] [Mailing List Home] [Home]