First O2 Sensor failure

[GiraffeMarineSalvage]

So basically I just wanted to share my experience and some graphs of my first O2 Sensor failure.
I did a fresh water dive yesterday, water temp 4C, max depth 30m, dive time around 1h with no-deco, and when diving back to the entry at 10m of depth I had one of the three O2 sensors showed way different values then the other 2 sensors did, with values ranging from 1.5 to 0 ppO2 at a SP of 1.2. I flushed and after watching the values I bailed out and ascended without problems and without panicking, still in the beginning of my ccr journey..

Thank you for giving us the opportunity to learn from your experience, I'm also very much in the beginning of gaining CCR experience so I appreciate thinking through real life "If ___, then __" situations (and I would have also bailed out at my current level of experience combined with simple risk/reward ratio of "when in any doubt..").
With that said, purely learning/thinking through things, in addition to points raised above of paying attention to mV history and concluding on loop with two trustworthy sensors confirmed by dil-flush, in context given how much would more experienced CCR divers consider safely ascending (whether bailed out or using trustworthy readings from two confirmed cells) from 10m to 6m to do cell limiting test?
Also, given my Triton has a pretty minimal loop volume would it be reasonable to think once at 6m or less, one could do O2-flush and go O2-only mode, and then at a constant depth attribute any decrease in buoyancy as a need to add O2 (thinking on mCCR, and clearly need to make sure ADV is off and one had already dialed in a truly minimal loop volume..). ie if and only if one was operating in 100% O2 mode with a truly minimal loop volume in less than 6m, or even on surface/land, with no dramatic depth/temperature changes, a loss of metabolized O2 from the loop would be naturally felt and signal a need to manually add O2 well before it would be a problem?

P.S. I emphasize these two questions are raised purely as hypotheticals, not advice and I'm thinking through what I might consider doing using a totally different CCR... (Triton).

 

[tomsch]

Thank you for giving us the opportunity to learn from your experience, I'm also very much in the beginning of gaining CCR experience so I appreciate thinking through real life "If ___, then __" situations (and I would have also bailed out at my current level of experience combined with simple risk/reward ratio of "when in any doubt..").
With that said, purely learning/thinking through things, in addition to points raised above of paying attention to mV history and concluding on loop with two trustworthy sensors confirmed by dil-flush, in context given how much would more experienced CCR divers consider safely ascending (whether bailed out or using trustworthy readings from two confirmed cells) from 10m to 6m to do cell limiting test?
Also, given my Triton has a pretty minimal loop volume would it be reasonable to think once at 6m or less, one could do O2-flush and go O2-only mode, and then at a constant depth attribute any decrease in buoyancy as a need to add O2 (thinking on mCCR, and clearly need to make sure ADV is off and one had already dialed in a truly minimal loop volume..). ie if and only if one was operating in 100% O2 mode with a truly minimal loop volume in less than 6m, or even on surface/land, with no dramatic depth/temperature changes, a loss of metabolized O2 from the loop would be naturally felt and signal a need to manually add O2 well before it would be a problem?

P.S. I emphasize these two questions are raised purely as hypotheticals, not advice and I'm thinking through what I might consider doing using a totally different CCR... (Triton).

For 6m you can just "Diluent flush" with oxygen and if you do that 2-3 times you can besure that you breathe at least like 70% oxygen. For everything deeper you can run it as a SCR but everything else is pretty risky.

 

[Superlyte27]

For 6m you can just "Diluent flush" with oxygen and if you do that 2-3 times you can besure that you breathe at least like 70% oxygen. For everything deeper you can run it as a SCR but everything else is pretty risky.

Why run it SCR? I make the math easy, but you have what you believe to be 2 good sensors. You can verify this by a dil flush. You have .21 in your dil. And you’re at 100’ or 4 ata. So you should have a PPO2 of about .84

If you have near that, you’re good to go. No need to bailout, no need to SCR. Just end your dive.

 

[RedSix]

Why run it SCR? I make the math easy, but you have what you believe to be 2 good sensors. You can verify this by a dil flush. You have .21 in your dil. And you’re at 100’ or 4 ata. So you should have a PPO2 of about .84

If you have near that, you’re good to go. No need to bailout, no need to SCR. Just end your dive.

And if you are to lazy to do the math, a Shearwater even has a function to show you the pO2 of your diluent at the current depth:

 

[tomsch]

Why run it SCR? I make the math easy, but you have what you believe to be 2 good sensors. You can verify this by a dil flush. You have .21 in your dil. And you’re at 100’ or 4 ata. So you should have a PPO2 of about .84

If you have near that, you’re good to go. No need to bailout, no need to SCR. Just end your dive.

I didn't meant when their is just one failure, even when all sensors fail for some reason it is still dive able with some care.

 

[Superlyte27]

I didn't meant when their is just one failure, even when all sensors fail for some reason it is still dive able with some care.

Agreed

 

[GiraffeMarineSalvage]

For 6m you can just "Diluent flush" with oxygen and if you do that 2-3 times you can besure that you breathe at least like 70% oxygen. For everything deeper you can run it as a SCR but everything else is pretty risky.

The O2 flush 2-3 times at 6m is exactly what I was thinking (with Triton it's really easy to compress counterlungs and achieve really efficient dil or O2 flush). Recently I found it surprising when cleaning a boat hull in O2 only mode after a mellow practice dive I was able to manually keep my PPO2's in a surprisingly narrow bandwidth (as confirmed by 3 working sensors, which of course was I continuing to monitor and with critical note being ADV was off...) based upon a perceivable loss of both bouyancy and less gas in the loop from O2 being metabolized...
My above observations are of course not at all a substitute for 2+ trusted O2 sensor readings, and easy to observe on mCCR vs likely unnoticed in eCCR, but I can't help but think they are potentially worthwhile details to be conscious of under 6m or less running as O2-only mode, which would dramatically improve off gassing than air bailout especially if a chain of multiple issues had collided, like hypothetically sensor(s) failure plus flooded dry suit (given a change from being warm during the first portion of dive to a cold ascent/deco increases DCS risk relative to cold2warm or cold2cold )?
(again just thinking through as many what-ifs as possible..)

 

[jale]

The O2 flush 2-3 times at 6m is exactly what I was thinking (with Triton it's really easy to compress counterlungs and achieve really efficient dil or O2 flush). Recently I found it surprising when cleaning a boat hull in O2 only mode after a mellow practice dive I was able to manually keep my PPO2's in a surprisingly narrow bandwidth (as confirmed by 3 working sensors, which of course was I continuing to monitor and with critical note being ADV was off...) based upon a perceivable loss of both bouyancy and less gas in the loop from O2 being metabolized...
My above observations are of course not at all a substitute for 2+ trusted O2 sensor readings, and easy to observe on mCCR vs likely unnoticed in eCCR, but I can't help but think they are potentially worthwhile details to be conscious of under 6m or less running as O2-only mode, which would dramatically improve off gassing than air bailout especially if a chain of multiple issues had collided, like hypothetically sensor(s) failure plus flooded dry suit (given a change from being warm during the first portion of dive to a cold ascent/deco increases DCS risk relative to cold2warm or cold2cold )?
(again just thinking through as many what-ifs as possible..)

Hi
If you had to BO and the unit is not flooded, it is not a problem to go back to the loop when you reach 6M. As you said, just make sure you do a proper oxy flush and you should be good
As a side note, when you use the Triton as a pure oxy rb only, be sure to close the flow-stop of the ADV as it is possible to open it with a bad move of your arm. Yes, it is rare but it can happen. You can put a zip tie at the flow-stop or you can replace the male inflator part by a plugged 9/16M-3/8F adaptor.
Enjoy your dives

 

[RedSix]

If you had to BO and the unit is not flooded, it is not a problem to go back to the loop when you reach 6M. As you said, just make sure you do a proper oxy flush and you should be good

If you went to BO because of CO2 this is not a good idea ;-)

 

[jale]

If you went to BO because of CO2 this is not a good idea ;-)

of course