This question has my google-fu stumped! Three gas nitrox?

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HamTrainChickenLaser

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OK first of all, this is the image that started me thinking:

Screenshot 2025-05-03 at 11.16.57 PM.png


What is "3 gas nitrox"? I hear folks say that if you want to get into technical diving then get a Teric, but for most recreational diving the Tern is fine. I just don't understand where technical diving and recreational diving split- is it only technical diving if I am going deeper than 130'? Or wreck penetration is also tec?

OC is open circuit- like normal scuba, and CC is a rebreather, true? So "OC TEC: Trimix enabled" and "3 gas Nitrox" are completely different from each other? One source that I found with google seemed to indicate that 3 gas Nitrox is "trimix" but that seems wrong.
 
I just don't understand where technical diving and recreational diving split- is it only technical diving if I am going deeper than 130'? Or wreck penetration is also tec?
In my view:
  • Deeper than 130 ft (usually requiring trimix to mitigate narcosis, though some still do it on air).
  • Staying beyond NDL (mandatory deco stops), typically involving richer O2 gas than the bottom gas. Improper switching has played a role in numerous fatalities.
  • Hard overhead (e.g., cave or wreck penetration beyond a swim through where the exit is visible).
  • Any combination of these.
The Tern would be fine for the NDL or overhead type of technical dives. It would not handle trimix.
 
I would read that as three different nitrox mixes on the same dive. i.e. 32%, 50% and 80%.
Diving Nitrox 32 and then doing decompression stops on Nitrox 50 and later on Nitrox 80 (or pure oxygen) is a very valid gas plan especially for long duration dives to 100 feet. I have done dives like these.
 
Diving Nitrox 32 and then doing decompression stops on Nitrox 50 and later on Nitrox 80 (or pure oxygen) is a very valid gas plan especially for long duration dives to 100 feet. I have done dives like these.

Yes, I've done a few dives like that in the distant past, but using 100% O2. I elected to give 80% as an example because I didn't want to get in to a ScubaBoard argument about whether 100% O2 was nitrox :)
 
Yes, I've done a few dives like that in the distant past, but using 100% O2. I elected to give 80% as an example because I didn't want to get in to a ScubaBoard argument about whether 100% O2 was nitrox :)
A clever choise.
The all know that pure oxygen is just 1% argon.
 

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