Switching gasses at depth?

[Blackwood]

Gosh, I thought that the Spare Air discussion was going to be the most contentious part of the thread, but now I see that we have a challenger!

I'm still stuck on the part about using a gas switching computer to go from backgas (air) to a Spare Air (nitrox).

 

[Rainer]

I'm still stuck on the part about using a gas switching computer to go from backgas (air) to a Spare Air (nitrox).

Really? I couldn't get past the part about putting (a lean) nitrox in the SA. That post is classic!

 

[Blackwood]

Really? I couldn't get past the part about putting (a lean) nitrox in the SA. That post is classic!

You got further than I did

I'm still busy picturing an OOG diver sticking a spare air in his mouth and then proceeding to fuss with his computer to see how much more NDL time the switch to nitrox gave him. "Oh cool, forty six more seconds! Too bad it took me a minute to navigate the menu system." I wonder if you can switch it from one gas to no gas.


Rstofer is a good guy, but that's just too funny to pass on.

 

[Rainer]

Spare Air: For when you wanna run out of gas twice.

 

[Blackwood]

Classic. I think you should propose that as their new tag line at the next DEMA.

 

[rawls]

I'm still stuck on the part about using a gas switching computer to go from backgas (air) to a Spare Air (nitrox).

 

[rstofer]

I think you need to look at the paragraph breaks.

The part about some dive computers having the capability of gas switches has absolutely nothing to do with the paragraphs about Spare Air. It isn't even mentioned in that paragraph!

The paragraph about lean Nitrox is simply to demonstrate that you can't arbitrarily put a mix in a Spare Air or pony bottle without considering where you might wind up using it. It is not a recommendation to actually use a Spare Air device or to put Nitrox in such a device. See the "If you really want to..." bit? No place in that paragraph did I say "I would..." or "I recommend...". What I did point out is that high pO2 is not a good thing.

Then there is the paragraph where I, rather politely if I do say so myself, point out the futility of Spare Air based on capacity. Yes, you will run out of air on ascent. It's inevitable. We all know this.

Now I have a paragraph suggesting an experiment to prove the ineffectiveness of Spare Air at depth. Another rather polite way of saying "it ain't gonna work!".

Finally, I point out a somewhat more capable backup tank size. Even then, it could be too small under some conditions. And anybody who believes their buddy is any part of a backup plan needs to give up diving and take up golf.

Richard

 

[Rainer]

Oh, never mind...

 

[Steve50]

And anybody who believes their buddy is any part of a backup plan needs to give up diving and take up golf.

Richard

Well - I really don't care for golf...but if I were to take up golfing, I'd want a buddy along as backup.

When that beverage cart comes around, if I find I've run out of money, I want to be able to use some of my buddies money - cause I wouldn't dream of playing golf without beer !

 

[Blackwood]

I think you need to look at the paragraph breaks.

The part about some dive computers having the capability of gas switches has absolutely nothing to do with the paragraphs about Spare Air. It isn't even mentioned in that paragraph!

Taken in the context of the the thread it does have to do with a Spare Air. But I knew in replying that you weren't seriously suggesting it. Just having a little fun here in trying to make a point (one that's been beaten to death).

The paragraph about lean Nitrox is simply to demonstrate that you can't arbitrarily put a mix in a Spare Air or pony bottle without considering where you might wind up using it.

I think given the limited time you could possibly be breathing the thing, it doesn't really matter how rich the mix is. You're on the way up anyway. Betcha you could make a pure oxygen spare air ascent starting at 100 feet and not run into toxicity issues.

But that's beside the point.

Worrying about the contents of a Spare Air is kinda like missing the forest for the trees. Big picture: you're going up, and getting the surface alive is the immediate goal.