CNS O2 lockout

[donfrazier]

Recently my Luna computer locked me out for 2 hours. Indicating a 40% value. I had finished my last Nitrox dive the previous day followed by two air dives. The last of which was ~160' on surfacing my computer informed me of its lock out. Any ideas on what's going on here. How can I violate CNS O2 saturation on air?

 

[BlueTrin]

I looked in the manual but I didn’t see a lockout for doing another five before it’s at 40%

https://ww2.scubapro.com/media/462264/galileo_luna_eng.pdf

If Galileo detects a situation of increased risk (due to the potential of microbubble accumulation from previous dives or a CNS O2 level above 40%), the symbol will appear on the display together with a suggested surface interval. This minimum surface interval is what Galileo predicts being necessary to reduce the number of microbubbles and/or to reduce the CNS O2 level below 40%.
You should not undertake a dive as long as the no-dive warning is displayed on the computer screen. If the warning is prompted by microbubble accumulation (as opposed to CNS O2 over 40%) and you dive anyway, you will have shorter no- stop times or longer decompression times. Moreover, the duration of the microbubble warning at the end of the dive can increase considerably.

 

[SetheryJ]

I'm new to technical diving, so I'm sure others will be more helpful. But, at face value when I looked at the tables you are only at a po2 of 1.23 at 160' on 21%. You would have to spend 30 minutes on the bottom to bring your cns% to 42.00 (15.38 OTUS). And that means you would have racked up somewhere over 45 minutes of deco AT LEAST.

There are quite a few variables to consider, but those are the rough numbers I found. Is it possible you left your watch in nitrox mode when you did your deep dive? I feel like that could be the most logical answer. That, or perhaps there is a problem with your computer?

Sorry I couldn't be more helpful.

Seth

 

[SetheryJ]

I re-read your post and have a question- Are you saying you did three dives in a single day, the first being on nitrox and the second and third being on air? Or are you saying you did a single nitrox dive one day followed by two deep air dives on the next day?

Depending on mix, depth, time of your preceding dives, I suppose it 'could' be possible to rack up some decent cns%/OTU exposure. We'd need all of the dive profiles, surface intervals, mixes, etc. to figure out the numbers.

Seth

 

[BlueTrin]

Can you post a picture of the screen of the computer?

 

[donfrazier]

I re-read your post and have a question- Are you saying you did three dives in a single day, the first being on nitrox and the second and third being on air? Or are you saying you did a single nitrox dive one day followed by two deep air dives on the next day?

Depending on mix, depth, time of your preceding dives, I suppose it 'could' be possible to rack up some decent cns%/OTU exposure. We'd need all of the dive profiles, surface intervals, mixes, etc. to figure out the numbers.

Seth

One dive on Nitrox during the previous morning One dive on air the afternoon before, one dive on air in the morning of the next day and the final dive on air in the early afternoon. I’m thinking the only probable answer is I left my computer in Nitrox mode. Pretty sure I checked it immediately. Thank all of you for ideas, Don

 

[SetheryJ]

One dive on Nitrox during the previous morning One dive on air the afternoon before, one dive on air in the morning of the next day and the final dive on air in the early afternoon. I’m thinking the only probable answer is I left my computer in Nitrox mode. Pretty sure I checked it immediately. Thank all of you for ideas, Don

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

 

[rvojr]

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=(160'/33 +1)*.32=1.87

 

[SetheryJ]

PPO2=(160'/33 +1)*.32=1.87

THANK YOU! Had I just went to my notes I would have found the equation lol. Cheers!!!

 

[rvojr]

THANK YOU! Had I just went to my notes I would have found the equation lol. Cheers!!!

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%.