Who's using 100% O2 for deco?

[Jax]

This is a super discussion! I love you guys!

So, where it is convenient to get 100% fills, people tend to gravitate to them.

Where booster pumps are not available, the ease of 80% has its attractions.

Hang time just isn't that different between 80% and 100%, unless you're one of those super-saturation nutcases like Akimbo. :joke:

The primary reason for 100% is because the team is doing it. . . . . Is that about it?

 

[Kern]

On normoxic dives I stick to EAN50 & O₂. I find a single bottle of EAN50 to be very versatile for accelerated deco in the 40-55mt, 20 - 30 minute range. Sure O₂ may get me out cleaner, but to date I'v never had as much as tirdness or a niggle using 50.

I'v just been playing around with V-Planner a little.

Have a look at the results for a dive to 55mt, for 20 min, with 21/35. With a single O₂ deco bottle it has a run time of 57 minutes. With a single EAN50 deco mix it has a run time of 50 minutes.

 

[jimmy71]

The wreckers I go with have been using 100% boat supplied for about 25 years now. Roll a 200 of welding O2 onto the boat, put on a high flow O2 welding regulator and drop a 5/16th hose down to 20’ with 2 to 4 2nd stages on 10’ whips.

WOW. That is such a smart way of doing it. I have seen it with air as back up so that people with poor gas management can complete there safety stops. Never with O2. I need to dive off some boats that cater to tech divers......................

 

[JeffG]

The primary reason for 100% is because the team is doing it. . . . . Is that about it?

No, the primary reason is because it has no inert gas.

A team can use any percentage it wants to.

 

[Thalassamania]

No, it is not.

There are still is a lot of this globe where you can get only air and100% O2 . The wreckers I go with have been using 100% boat supplied for about 25 years now. Roll a 200 of welding O2 onto the boat, put on a high flow O2 welding regulator and drop a 5/16th hose down to 20’ with 2 to 4 2nd stages on 10’ whips.

Nowadays, we will plan for our dives on back gas plus one deco gas that we carry. If we miss the up line to the boat and 100% O2 whips (never happened to me but it is planned for), we do a drift deco on what we carry. If we make it back to the boat and the 100%, we use it as the 2nd deco gas and get out of the water quicker. ...

Same here, with the ability to swap scuba bottles in, in case you want air for some reason or need air for breaks in an IWR situation.

 

[Ste Wart]

I use a 51.2% and 78.7% generally.

Probably says more about my blending ability really.....

 

[Levigarrett]

This is a super discussion! I love you guys!

So, where it is convenient to get 100% fills, people tend to gravitate to them.

Where booster pumps are not available, the ease of 80% has its attractions.

Hang time just isn't that different between 80% and 100%, unless you're one of those super-saturation nutcases like Akimbo. :joke:

The primary reason for 100% is because the team is doing it. . . . . Is that about it?

So if you're using 80% will you hang for the entire USN obligation or will you still take a reduction? If you're doing the full hang on 80%, then I think you can add that as another reason save the fact that the team is doing it.

 

[divereh]

I prefer using an 80 mix if there has been alot of deco on the dive , just for the reason it reduces pulmonary toxicity, and a little easier on the respertory track. Go do a 3 hour dive and you will know what I mean.

 

[Slamfire]

You are trying to outgass N2. There is no competing N2 in-gassing with pure O2 because there is absolutely no N2 in it. In 80/20 the (low) partial pressure of N2 works against you a bit.

Isn't 80/20 a heliox mix? As such there wouldn't be any N2 in it. As amusing as GI3 article reads, I think he was discussing something slightly different than what we are here. We are talking about 80 nitrox vs 100 % O2 whereas GI3 was talking about 80/20 heliox vs 100% O2. I tend to agree with the GI3 premise that choosing 80/20 because there is some lacking buoyancy control issue is a bad idea. Get your buoyancy under control first and then move on to this kind of dives.

Before moving to Canada I was a tropical diver. I knew what good buoyancy control felt like. After doing my first cold water dive I knew I was very far from having good buoyancy control under these conditions. Having all that floaty rubber for exposure protection along with the comparatively "vast" amounts of lead I had to carry in order to sink, made me feel like I knew nothing about buoyancy. I resolved to get the buoyancy issue under control before moving on to the complexity of drysuits. It was only until my 96th cold water dive that I tried a drysuit, even though buddies, dive shops and instructors had been pushing me to get on a drysuit much earlier.

I also see the merit of wanting to be deeper when the seas are rough. I'm prone to motion sickness and throwing up under water is no fun. I would also think that the motion sickness stress and the dehydration from throwing up would increase DCS likelihood.

The thought of filling a 40cf only two thirds full, just to stick to the 100%, causes niggles. . . . I'd rather carry max capacity of 80% than to dive with a partial fill bottle.

I went to my closest gas supplier (not a dive shop) and asked him to fill my Al40 with 100%. He said he could give me about 2000 to 2200 psi of 100% or he could top that up with air to give me a full tank of ~80%. When using him I choose the latter. You can never have too much gas.

It came in handy 2 weeks ago on my last dive trip to the island. After doing some boat dives, my friend and I decided last minute to do a shore dive in Madrona Point which was on our way to the ferry. It just so happens this day was a statutory holiday and there was nobody available to fill up tanks anywhere. Using up left overs from stage and deco bottles and 1 HP steel 80 filled up to 3500 psi of 32%, I was able to transfill 2000 psi of what ended up being 40% nitrox into my doubles. I would not have been able to transfill in that much if I had been in the practice of carrying Al 40's that are only 2/3 full. And before anybody asks, I wasn't able to use the steel 80 because I had no rig for a single tank available to me and transfilling was a more attractive idea than going around slinging a steel 80 with empty doubles on my back.

 

[Dive Bug Bit Me]

Isn't 80/20 a heliox mix? As such there wouldn't be any N2 in it. As amusing as GI3 article reads, I think he was discussing something slightly different than what we are here. We are talking about 80 nitrox vs 100 % O2 whereas GI3 was talking about 80/20 heliox vs 100% O2. I tend to agree with the GI3 premise that choosing 80/20 because there is some lacking buoyancy control issue is a bad idea. Get your buoyancy under control first and then move on to this kind of dives.

I agree that choosing 80 mix because you have bad buoyancy is a poor decision. If you have poor buoyancy you shouldn't do deco profiles. My issue with GI3's statement is that he implies you should always choose 100% because your superior skill will keep you safe (else you are a "stroke"). I take issue with always choosing the more risky gas because your superior skills will keep you safe.

I would rather develop superior skills and then try keep myself out of situations where I need them to stay alive. I will always try build in as much safety factor as I reasonably can. If that makes me a "stroke" then may I at least be an alive "stroke".