New to OTU and CNS: hints?

[Roberto Inzerillo]

Good day :-)

I'm relatively new to scuba and learning how to use Subsurface Divelog in the meanwhile.

How should I read/understand OTU (Oxygen Toxicity Units) and CNS (Central Nervous System Oxygen Toxicity) values?

E.g. something like this (it's a webview screenshot): 

That's taken from a friend's log, only air, max depth 38m.

Is the CNS value maybe a percentage? Of what exactly?

At https://www.liveabout.com/oxygen-toxicity-and-scuba-diving-2962843 I read "A diver's OTUs should not exceed about 615 in a day". is that reasonable?

I'd like to put those numbers in perspective in order to understand what they mean in real life and how to "read" my own logs.

[Jason Bramwell]

Until you are tech diving you can pretty much ignore them. If you take a nitrox class that’ll explain it to you.

Jason

Sent from my iPhone

On 3 Feb 2020, at 11:57, Roberto Inzerillo <roberto....@gmail.com> wrote:



Good day :-)

I'm relatively new to scuba and learning how to use Subsurface Divelog in the meanwhile.

How should I read/understand OTU (Oxygen Toxicity Units) and CNS (Central Nervous System Oxygen Toxicity) values?

E.g. something like this (it's a webview screenshot): 

<Clipboard01.png>

That's taken from a friend's log, only air, max depth 38m.

Is the CNS value maybe a percentage? Of what exactly?

At https://www.liveabout.com/oxygen-toxicity-and-scuba-diving-2962843 I read "A diver's OTUs should not exceed about 615 in a day". is that reasonable?

I'd like to put those numbers in perspective in order to understand what they mean in real life and how to "read" my own logs.

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[Robert C. Helling]

Am Montag, 3. Februar 2020 12:57:19 UTC+1 schrieb Roberto Inzerillo:

Good day :-)

I'm relatively new to scuba and learning how to use Subsurface Divelog in the meanwhile.

How should I read/understand OTU (Oxygen Toxicity Units) and CNS (Central Nervous System Oxygen Toxicity) values?

E.g. something like this (it's a webview screenshot): 

That's taken from a friend's log, only air, max depth 38m.

Is the CNS value maybe a percentage? Of what exactly?

At https://www.liveabout.com/oxygen-toxicity-and-scuba-diving-2962843 I read "A diver's OTUs should not exceed about 615 in a day". is that reasonable?

That's correct, CNS is supposed to be a percentage (with the recommendation to stay below 80%) while OTU is a dimensionful number with the recommendation to stay below 300 (for a conservative view) or the 615 that you quote, In any case, in most of the dives, the CNS value is much more limiting. For some more background on both, there are two articles in my blog:  https://thetheoreticaldiver.org/wordpress/index.php/tag/oxygen/ 

[Roberto Inzerillo]

Il giorno lunedì 3 febbraio 2020 14:03:17 UTC+1, Robert C. Helling ha scritto:

That's correct, CNS is supposed to be a percentage (with the recommendation to stay below 80%) while OTU is a dimensionful number with the recommendation to stay below 300 (for a conservative view) or the 615 that you quote, In any case, in most of the dives, the CNS value is much more limiting. For some more background on both, there are two articles in my blog:  https://thetheoreticaldiver.org/wordpress/index.php/tag/oxygen/ 

Interesting reading :-)

Vielen Dank, Robert ;-)

It's clear to me (from your answers) that I will not need to care for OTU and CNS as long as I dive recreationally under 30m. But I understand OTU and CNS are not zero even at 30m. Is it just that those numbers remain well under any alarming value at this depth?

[Robert C. Helling]

Am Montag, 3. Februar 2020 14:25:05 UTC+1 schrieb Roberto Inzerillo:

It's clear to me (from your answers) that I will not need to care for OTU and CNS as long as I dive recreationally under 30m. But I understand OTU and CNS are not zero even at 30m. Is it just that those numbers remain well under any alarming value at this depth?

As long as your are only breathing air and not higher oxygen nitro, you will never even get close the interesting levels. You can try this yourself in the planner. Even a dive to 40m with 120min of bottom time (which requires 500min of decompression) gets you to 44% CNS and an OTU of 131.

Best

Robert 

[Roberto Inzerillo]

Cool.

This short discussion has put a touch of real-life meaning to those numbers.

Thank you so much :-)