Who's using 100% O2 for deco?

[Akimbo]

I'm keenly aware of the controversy of using 100% O2 which is why I was surprised to see it's use being advocated during my recent AN/DP class...

I have been using pure O2 on in-water decompression stops since the early 1970s on military, commercial, and recreational dives; for standard and surface decompression profiles. I have often used pure O2 for additional safety margin using schedules based on air stops when a chamber was not onboard. I fail to see any controversy since the practice has been in use well before Cousteau and Gagnan invented the demand regulator for divers.

 

[Dive Bug Bit Me]

What was the profile?

31 mins bottom time at 130 ft on 25%, followed by VPM deco on 50%.

We added a deep stop at 70 ft and did the gas change there. Ended up being a 4 minute deep stop for the 3 of us to follow change protocol.

 

[gsk3]

31 mins bottom time at 130 ft on 25%, followed by VPM deco on 50%.

Why do you think that would be much shorter on 100%? DecoPlanner with VPM shows 20 minutes on 50% vs. 19 minutes on 100%. 20/85 GF shows 18 minutes on 50% and 19 minutes on 100%.

And they were diving 25/25, which means they weren't sticking strictly to their training anyhow. I've not yet met a GUE T1 diver who blindly followed every guideline....

 

[Dive Bug Bit Me]

Why do you think that would be much shorter on 100%? DecoPlanner with VPM shows 20 minutes on 50% vs. 19 minutes on 100%. 20/85 GF shows 18 minutes on 50% and 19 minutes on 100%.

And they were diving 25/25, which means they weren't sticking strictly to their training anyhow. I've not yet met a GUE T1 diver who blindly followed every guideline....

Can't comment on GUE guidlines and standards or how they are followed. I can say GUE trains some of the best divers out there.

With regard profile, I was pushing to take tanks of both 100% and 50% on the dive. Buddies said no go and insisted on doing the deco on 50%. Still felt safe so I went along with the plan.

 

[gsk3]

With regard profile, I was pushing to take tanks of both 100% and 50% on the dive. Buddies said no go and insisted on doing the deco on 50%. Still felt safe so I went along with the plan.

Ah, I get it. That'd be because they aren't trained in two-bottle dives.... OTOH, people seem to often do AN/DP first, about which my understanding is that it does generally train you for 2 deco mixes.

I can see the frustration at the chilly waters

 

[Thalassamania]

Green gas is good gas - Billy Bob Hamilton.

 

[Jax]

Surprisingly if I am given a choice I will tend towards 80% for the benefits of changing sooner and being a little more forgiving (anything that reduces risk is OK by me). Interestingly I just ran 80% and 100% on I-deco (30 /80 gradients, last stop at 20ft) for a 55 min dive to 100ft on air. 80% had the shorter run time (by one minute).

Advantage to 80% in the above scenario (in addition to the shorter run time) is that your CNS loading is only 32% compared to 51% on O2. Point is that there are some situations where 80% can give a more optimal outcome.

Why do you think that would be much shorter on 100%? DecoPlanner with VPM shows 20 minutes on 50% vs. 19 minutes on 100%. 20/85 GF shows 18 minutes on 50% and 19 minutes on 100%.

And they were diving 25/25, which means they weren't sticking strictly to their training anyhow. I've not yet met a GUE T1 diver who blindly followed every guideline....

Thank you. That's what I had been finding in running the schedules.

 

[down4fun]

i understand things are a little different for me since I am on ccr but I, or we, still have to plan for o/c deco should we have to bailout. For dives to 150-160 Tony and will each carry a bottom gas and then one will carry 50% and one 100%. That way we could each get out of the water alone, but together (assuming just one of us had to bail which is reasonable) we would have both deco gases to accelerate things. For deeper dives beyond 200ft we plan on two deco gases, usually being 50% and 100%. the 50% lets you get on a deco gas earlier and helps reduce the amount of bottom gas you have to carry and they switch to 100% to bring down the total deco time.

So yes lot's of peeps still using 100% for deco

 

[rigdiver]

I've always used 100% just because I could. Kinda neat to see your deco obligation go from an hour to 20 minutes just by pushing a button and telling the computer we're on 100% now.

 

[lowviz]

To me, the difference in hang time using accelerated washout with 80% or 100% is minimal. In fact it is nonexistant, I use the IANTD >75% table for either. So why not go for what is slightly better? In good conditions I'll take 100%.

However, in rough seas I'd rather not play bumper cars at 20' with everybody that brought 100%. Add to that the really, really remote chance that I might tox by being tired, cold, and too deep, why not bring 80% and fly by computer, still checking with tables?