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

[Michael Guerrero]

Lol, you forgot to end your post with flame on!

 

[decompression]

I'll stick with 50 and 100, let's start deco early and then kick it to the curb!


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[kwinter]

Put me in the 80% camp. For the same reasons Victor and I have shared in the past. Deco on 80 vs 100 will add a few minutes to the total deco time, but drastically reduce O2 exposure and the risk of OxTox. If you cut deco short, you might get bent. That will usually happen about an hour later when you are on the boat or dry land with O2 and help available. If you have an oxygen induced seizure while underwater even at your 10 foot stop you are probably going to die. The O2 clock is relentless. And even though there is only a very small chance of OxTox, the consequences are dire. I think the way I posted in a thread on RBW was "I'd rather be in a helicopter on the way to the chamber than under a tarp on the way to the morgue."

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!!!

What a crock of s*it.

 

[Michael Guerrero]

I'll stick with 50 and 100, let's start deco early and then kick it to the curb!


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This is a clear and blatant parameter violation. Further transgressions won't be tolerated. One gas only people.

 

[TONY CHANEY]

Actually neither but I have used both. In this case I would go with the 80%. I can jump on it faster deeper and if you run the tables having 100% creates more precautions (such as diving in rough seas) than the benifit of only a few minutes of deco difference. i.e. A 100' dive on air with 100% deco for 22 minutes would be 5 minutes of deco. It is also five minutes of deco with 80%. This is based on Pastodeco just in case you want to know.

Another factor to consider, per the CGA, to pressurize a tank past 2200 psi with 100% if I remember correctly. So you will get a low fill.

 

[Dr. Lecter]

Another factor to consider, per the CGA, to pressurize a tank past 2200 psi with 100% if I remember correctly. So you will get a low fill.

I'd get a new fill monkey, because that one is clearly broken.

 

[Scubadude_LA]

I use what is onhand. I lean toward 80%. The "quicker" is true for 100 but the difference is very small in the big picture. Run a planner and see for yourself. I dive cave and open ocean, I definitely prefer 80 in the ocean. 100 is easier to mix, just boost. Generally you are gonna be mixing other gases anyway, so I don't see the mixing part as such a big deal.
My trimix instructor taught us on 80. He had points to back up his decision, some mentioned in this thread, rough seas, cns/otu, etc.
One of the things mentioned that sticks in my mind most was, when you hang longer on bigger dives you will breath 100 for 20 minutes burn your lungs, then take an air break, then do it all over again. 80%, just keep breathing 80%...

 

[doctormike]

According to my tech instructor, there is a significant safety advantage in terms of fire with 80% when compared to 100%, especially when a tank is overfilled. So he recommended using 80%. Also, depending on your profile, 80% may get you out of the water quicker, since you can switch to your deco gas sooner.

I guess there might be a surge advantage as mentioned above, although you would have the same issue, only at 30 feet instead of 20 feet.

On the boat, if someone needed oxygen, I agree that 100% would be better, but I wouldn't say that 80% would be unacceptable.

 

[GrimSleeper]

100% because it's easier to mix.

LOL. And true. Hate blending 80%.

Since the benefit of using higher fO2 gasses in decompression lies in the increased gradient between the tissue tension of inert gas (and the pressure of inert gas in bubbles already formed, if you want to get really thorough) and the inspired partial pressure of inert gas, breathing no inert gas on the longest stop makes sense to me in terms of doing a really 'clean' decompression.

Having got bent doing air decompression from an air dive, and having felt very good after decompressing on 50% and 100% after much bigger dives, I tend to lean strongly towards as little inert gas as possible on the way up...

 

[TONY CHANEY]

I'd get a new fill monkey, because that one is clearly broken.

We know what really happens but I was just stating the facts. That is why you have to have a booster to pump O2 at higher pressures.