If you had to choose, 80% or 100% for deco gas and why.

[Michael Guerrero]

Interested to hear the different perspectives on this and to see if the reasons are similar to my own. If you respond, please stay on topic with which of the two (and only two) options, and why. Please don't list a bunch of other deco gases you use, or tell me it depends. Humor me, pick one, and give me the reason.

Thanks,

Mike

 

[Superlyte27]

Uh oh... here we go again.

You might be better served to search for this. You'll find a heated debate by both sides, most people of which really don't know what the heck they are talking about.

 

[Akimbo]

This isn’t complicated. You want the highest PPO2 to accelerate decompression and the longest stops are at 20 and 10'.

 

[Michael Guerrero]

Lol, I guess I need to make my initial post even more clear that I'm looking for each person's individual opinion and reasons for how they do it. Akimbo, I'm gleaning from your reply that you would pick 100%.

Superlyte,

I have. But what do you use and why?

This sincerely is not meant to be a religious debate. If all posters would ignore all other replies and just respond to my initial post I'd be happy as a pig in sh!t.

Mike

 

[Akimbo]

Lol, I guess I need to make my initial post even more clear that I'm looking for each person's individual opinion and reasons for how they do it. Akimbo, I'm gleaning from your reply that you would pick 100%...

No matter how I run the numbers the average PPO2 per minute during decompression is higher with 100%… unless we include saturation decompression.

 

[victorzamora]

I think the consensus is generally that for diving where surge is an issue, 80% lets you have safer stop margins. For caves or other circumstances where surge is NOT an issue, 100% is fine. The biggest factor in my decision was running deco profiles through my preferred planner until I was blue in the face and comparing 100% to 80% runtimes. O2 typically gets me out of the water quicker. Also, the VAST majority of my diving (and nearly all of my deco diving) is in a cave. I have zero concern over surge, and can deco out at literally any depth I deem necessary/beneficial. If I were diving a cave where a 20ft stop were impractical (crazy silty, tight room at 20ft or whatever) and I really needed to push my long stop lower, I'd switch to whatever deco mix made more sense. Until then, O2 for me.

 

[Michael Guerrero]

No matter how I run the numbers the average PPO2 per minute during decompression is higher with 100%… unless we include saturation decompression.

True statement. Is that your only consideration?

 

[Dr. Lecter]

I can't give you an answer because you haven't said what dive it'd be for. Saying one is always preferable to the other is unsupportable IMO. CNS numbers for the same dive finishing with 80% vs. 100% will be different, sometimes dramatically so. How much you care about that will depend on a lot of things.

I started with 80%, used 100% a few times, and moved onto CCR before I decided whether I really thought the difference in deco efficiency vs. CNS loading mattered that much to me. The more I dive, the less I think the surge argument matters. Rarely and momentarily hitting 1.6-2.0 because some surge dropped you a bit is really NBFD.

I carry 100% now simply because it's a dual use gas for CCR, but if I'd planned a huge dive and wanted to stack the CNS deck in my favor, I might carry 80s of 80% rather than 100% for BO.

 

[nadwidny]

100% because it's easier to mix.

 

[danvolker]

100%....It is better at 20 feet deep.....and if someone needed O2 on the boat after a dive, the 100% is perfect, the 80/20 is not acceptable. Considering the possibilities for dual need, 100% is the only way to go...
Also...anyone that can't hold a stop depth at 20 feet for the O2, whether in 4 foot waves or 8 foot waves, has no business doing tech dives!!!