CNS O2 lockout

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You're welcome. I'm not clear where the 32% came from and just assumed I missed it. I only saw Nitrox mentioned. 1.4 ppo2@160' is 24%.

Sorry, I should have specified. I chose 32% as a "standard" recreational blend that divers would likely use. I just picked that number out of thin air to make my calculations.

Seth
 
You're welcome. I'm not clear where the 32% came from and just assumed I missed it. I only saw Nitrox mentioned. 1.4 ppo2@160' is 24%.
Thank you all! I believe that my Luna was recommending a two hour surface interval before the next dive. Not the lock out I was interpreting from the warning. Once again thank you all for the input. You are a great source of knowledge. Good evening.
 
Thank you all! I believe that my Luna was recommending a two hour surface interval before the next dive. Not the lock out I was interpreting from the warning. Once again thank you all for the input. You are a great source of knowledge. Good evening.


Cheers! Happy diving.

Seth
 
If that is the case, that explains everything. At 130' your po2 on 32% is 1.6. At 1.6 for 20 min you are at 44.44 CNS% and 38.48 OTUs. My tables won't even tell me what p02 you'd have at 160' using 32EANX (I'm guessing 2.0?) If you couple that with your residual then you would most likely EASILY exceed your watch's 40% warning/lockout.

Still hoping a more seasoned tech diver can check my work and make sure I'm not giving you bad advice....

Seth
PPO2 at 160' 32NX is 1.88, ah damn should have read everything before replying. All sorted?
 
Generally, the standard accepted limit for CNS oxygen toxicity in diving is 80%. The computer in this case wants you start a dive with less than 40% of the CNS limit having been consumed by previous dives. That would give you 40% to use for a recreational dive. Which would give you 1 hour at a 1.4 (150*.4=60 minutes). 150 is the single dive exposure limit for 1.4.

Oxygen toxicity decays with a 90 minute half time. So in other words if you finished a dive at 80% oxygen toxicity than 90 minutes after surfacing you would be at 40%.

In this case if your computer wanted you to sit out for two hours in order to get your CNS % below 40% than that would indicate that your CNS% was already at 100%

N(t)=No (1/2)^(t/90)
or
0.4=1*(1/2)^(120/90)

Where 1/2 is a set value associated with half life time, 90 minutes is the half life for CNS% and t is the two hours it wants you to wait to get to .4.

The CNS percentage itself is a combination of time and PO2, which other have covered here.
 

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