Quote: (Originally Posted by
sabgia)
I aknowledge the existing CNS guidelines likely err on the side of caution, but ... running a default bottom SP of 1.3 (or higher) seems an unnecessary risk. Wet and/or limited cells could be lying to you and you could easily be at a 1.5-or worse, + have a significant deco-obligation, not to mention a spike cause by a stuck valve/solenoid or mistake.
Do peaple believe the added value of 1.3++ bottom SP justifies the risk?
Suggested for this thread is the practise of bottom SP's = 1.0-1.2, as per the literature available in this forum and library.
Fix the
problem rather than making allowances for it.
Don't dive a rebreather that allows wet cells (you know which ones they are)
Don't dive current limited cells
From a stuck solenoid perspective it will make bugger all difference what setpoint you start with - the rise in PPO2 will be damn fast at depth
The best setpoint at each stage of the dive depends on the dive profile.
For some dives the bottom ppo2 maybe 1.0 - for others it could be 1.3
When you dived OC what PPO2 did your gas usually give you during the working/bottom part of the dive??? (and please dont give me that padi bs about the constant ppo2 of a Rebreather making one more likely to tox so we must limit bottom ppo2 - that makes no sense if you compare to a properly staged OC dive to same depth - the deco is the same the CNS exposure is the same, or in some cases can even be less with the RB )
IMO the CNS clock as commonly taught is largely BS.
What I believe is more important is what you are doing (exertion wise) at that moment for a given PPO2.
So I limit bottom PPO2 if;
1) There is no benefit from a deco perspective in increasing it (i.e. a deep dive)
2) There is high degree of exertion, fighting strong currents ect
3) Its a long dive (8hours+)