Mailing List Archive Mailing List Archive
>On 2/10 Michel Therrien wrote: >>>You should consider taking five minutes air-breaks every 20 or 25 >minutes.<< > Jesse wrote: >I wonder why this is being suggested. Most people would say "to back the CNS >clock down," but I am not sure this is valid. Current thinking, as I understand >it, is that the %CNS clock "decays" or resets at a half life (or better, >half-time) of 90 minutes. In other words, if you were at 100 %, after 90 >minutes you would be at 50% and after 180 minutes you would be at 25 % and so >on. If you are decoing at 20 feet on pure O2, and are at, for example, 100% of >your CNS clock, five minutes will bring you down to something like 97.25% >(somebody check my math). I checked your math and it would be 96.2223836894%. Seriously, this mathematical approach to determine the CNS clock is very practical for us, but math. formula should not replace common sense. I'm not sure of the origin of that method of determining residual CNS toxicity, but I believe it comes from the technical diving community (probably by Dr. Hamilton for IANTD). My belief is that the exponential decay formula was created only by using the NOAA assumption that after 12 hours the CNS clock is reset. I am sure that Tom Mount could correct me on that one. The procedure of taking air-breaks every 20-25 minutes does not depend on the %CNS. I don't know what is the origin for the procedure. However, we can read about it in many sources. That procedure is specified in the DCIEM Diving Manual. I also remember reading about it in AquaCorps (Volume 3, page 32). Michel Therrien m.therrien@ne*.qc*.ca*
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]