Do I need separate nitrox and air pony/bailout tanks?

[Charlie99]

If you run out of gas at 120 feet and you've got Nitrox 38% in your bailout bottle, are you going to wait until you reach the MOD of 38% to start breathing from your bailout bottle?

I would feel relatively safe using EAN38 for emergency bailout at 120' because oxygen toxicity is dependent upon both ppO2 and TIME. The NOAA standard limit at 1.6ata is 45 minutes. EAN38 at 120' is still within the exceptional exposure limit of 1.8ata ppO2 (and obviously lower than the old exceptional exposure limit of 2.0ata). And you aren't going to be hanging around at 120' for more than a minute or two.

Just fill the bailout bottle with air.

Agreed. Much simpler. Less CNS risk at the cost of a very, very, very slight increase in DCS risk.

As noted in my first post of this thread, I'd use air in the pony/bailout, but people should understand that CNS toxicity is not a go/no go phenomena dependent solely upon ppO2. It is a combination of ppO2 AND LENGTH OF EXPOSURE to that ppO2.

 

[lenbro]

I appreciate the info. and the fact that posters explained things further than "just use air." It helps me learn.

 

[halocline]

I asked this same sort of question when I was a novice diver.

If you run out of gas at 120 feet and you've got Nitrox 38% in your bailout bottle, are you going to wait until you reach the MOD of 38% to start breathing from your bailout bottle?

Just fill the bailout bottle with air.

I hope the instructor said something like "if you run out of gas at 120 feet you've got more problems than a bailout bottle can solve."

But yes, I guess that is the typical rational for using air in a pony, and if I were going to use one, I'd use air. Getting a separate pony for nitrox is being the sort of customer dive shop owners have wet dreams about.

I wanted to thank Knowone for the delightful mixed doubles post, but it looks like the thanks button is gone.

 

[Dr Wu]

The Internet.

A library? No.

Learning less faster? Yes.

Can I put Bourbon in one and Scotch in the other.

I gotta ask.. whats with the Sharpie abuse?

And the steel rings on the neck..whut they for?

 

[GrumpyOldGuy]

I hope the instructor said something like "if you run out of gas at 120 feet you've got more problems than a bailout bottle can solve."

But yes, I guess that is the typical rational for using air in a pony, and if I were going to use one, I'd use air. Getting a separate pony for nitrox is being the sort of customer dive shop owners have wet dreams about.

I wanted to thank Knowone for the delightful mixed doubles post, but it looks like the thanks button is gone.

Try the like button Sherlock.

 

[Diverdown269]

.....If I were diving past the NDL or using a pony to extend dive time........

I dive Nitrox most of the time. My pony only has air in it.

If your diving past the NDL tables then your no longer carring a pony. Your carring a stage bottle.

I am concerned about the comment above... what do you mean if you were using your pony to extend dive time ?

Tim

 

[Teamcasa]

<Snip> If I were diving past the NDL or using a pony to extend dive time I would be more worried about matching gases....

Just a friendly comment, Pony's are not intended to extend your dive time. Thinking they are is just dangerous a best.

 

[lenbro]

It was sloppy wording on my part. I do know it would be a stage bottle if past the NDL's and that a pony should not be used to "make a bigger tank." I was trying to convey that I would not do those things but I didn't word it well. My dive plans will be within NDL limits and within the gas available in my primary tank. The pony would be emergency only - and hopefully seldom if ever used.

 

[halocline]

Try the like button Sherlock.

Why thank you, Watson. On my computer the "like" button is not a button, but the "like" does appear when I scroll over the lower right part of the post.

 

[Couv]

I gotta ask.. whats with the Sharpie abuse?

Knowone thinks you're a sharpie.