Nitrox mix in pony bottle

[Rick Murchison]

...I would be interested to hear the views of more experienced people on the board what they do if they are going below 200' carrying a pony bottle...

I'd put deco gas in it.
Or Argon.
Rick

 

[Scared Silly]

I would not be at 200' carrying a pony bottle. May be at 100'. But I would be carrying a pony but slinging it.

I would agree with Rick, I would prefer to have the same gas in both my pony and back gas. Filing one is the same as filling both. But I can see being lazy and having EAN 21 in it.

 

[Rhone Man]

EAN 21

That's normally my preferred mix when I am immersing myself in di-Hyrdogen oxide.

 

[DeepSeaExplorer]

I think you have to first decide if your pony is a redundant gas supply or a deco bottle. A pony bottle is generally assumed to mean redundant gas source for recreational diving. So when you say pony bottle, I assume that's where your thought process is.

If it's pony bottle for redundant gas supply, then Air is the most appropriate gas because it's good for all the diving that you are doing. And, you don't have to jack around with dumping the unused air to change to another mix to match your bottom gas.

If it's a deco bottle, then select an appropriate deco gas for the dive and don't plan on using it below the MOD. Then, you are no longer carrying a redundant gas source and it's no longer a pony bottle and is now a deco bottle.

 

[Scared Silly]

That's normally my preferred mix when I am immersing myself in di-Hyrdogen oxide.

Don't you mean Dihydrogen Monoxide??

 

[Rhone Man]

Don't you mean Dihydrogen Monoxide??

My bad; yes, I did.

 

[Reg Braithwaite]

I would be interested to hear the views of more experienced people on the board what they do if they are going below 200' carrying a pony bottle. Would you normally put a hypoxic mix in the pony? Or live with toxicity risk of deep air?

A bunch of people have said, "No pony," but let's work it out from first principles. We're diving to a little over 200'. Our ppO2 would be 1.5, well over the conservative limit of 1.4 and way over the conservative choice of 1.2 or less. Now, we are going to be stoned to the bone on air, but this is about a pony bottle and a single tank, so let's assume air is acceptable in the bailout bottle for the sake of the next paragraph.

Let's plan our emergency procedure. We need a deco plan of some sort, we are not going to fool around doing a direct ascent from 200'. I am going to pull a plan out of my ass, so if you dive this schedule you will probably die. I am just using it to illustrate a point.

Here's our deco plan:

• 3 minutes: ascend from 200' to 110'
• 2 minutes: at 110'
• 2 minutes: at 70'
• 2 minutes: at 50'
• 2 minutes: at 30'
• 2 minutes: at 20'
• 7 minutes: at 15'

So, what kind of pony are you carrying? Assuming you spend the full five minutes and then have an OOA, then spend a minute figuring that out, you are going to need 60 cubic feet of gas to get back home assuming a stressed diver SAC rate of 1 cubic feet per minute at 1 atmosphere.

Rock Bottom and Gas Management for Recreational Divers

In other words, you are going to need an AL80, even a 40 won't cut it for a 200 foot dive on air. Now honestly, if you're carrying 60 cubic feet of pony gas... shouldn't you consider doubles instead of a bailout bottle?

Now, we can abbreviate the deco. We can dive a bottom mix with a lower END. We can carry a deco bottle with a richer mix (like EAN50) for use above 70'. We can do a lot of things. But the basic point is, at 200', we need so much air that a single tank with a bailout bottle is no longer any advantage over doubles.

 

[texdiveguy]

A bunch of people have said, "No pony," but let's work it out from first principles. We're diving to a little over 200'. Our ppO2 would be 1.5, well over the conservative limit of 1.4 and way over the conservative choice of 1.2 or less. Now, we are going to be stoned to the bone on air, but this is about a pony bottle and a single tank, so let's assume air is acceptable in the bailout bottle for the sake of the next paragraph.

Let's plan our emergency procedure. We need a deco plan of some sort, we are not going to fool around doing a direct ascent from 200'. I am going to pull a plan out of my ass, so if you dive this schedule you will probably die. I am just using it to illustrate a point.

Here's our deco plan:

• 3 minutes: ascend from 200' to 110'
• 2 minutes: at 110'
• 2 minutes: at 70'
• 2 minutes: at 50'
• 2 minutes: at 30'
• 2 minutes: at 20'
• 7 minutes: at 15'

So, what kind of pony are you carrying? Assuming you spend the full five minutes and then have an OOA, then spend a minute figuring that out, you are going to need 60 cubic feet of gas to get back home assuming a stressed diver SAC rate of 1 cubic feet per minute at 1 atmosphere.

Rock Bottom and Gas Management for Recreational Divers

In other words, you are going to need an AL80, even a 40 won't cut it for a 200 foot dive on air. Now honestly, if you're carrying 60 cubic feet of pony gas... shouldn't you consider doubles instead of a bailout bottle?

Now, we can abbreviate the deco. We can dive a bottom mix with a lower END. We can carry a deco bottle with a richer mix (like EAN50) for use above 70'. We can do a lot of things. But the basic point is, at 200', we need so much air that a single tank with a bailout bottle is no longer any advantage over doubles.

It's great seeing fellow divers thinking and wondering....but it would appear you have stepped beyond your understanding of decompression diving with the above example,,,,I might recommend the appropriate training, the internet and this forum is not the correct place for such advanced advise or training.

I strongly would suggest to any reader of this thread to first understand a PONY BOTTLE is a cylinder that it's SOLE purpose in life is the carry a contingency gas of some type...air being a great one....it is NEVER to be considered for deco diving.

A diver with a single tank on his back carrying a PONY bottle at 200ft. has a whole list of **** to be concerned with!

Now I am no expert in these matters but it seems like this thread has really started to stray from the OP's intent in his original question....of which received some solid replies early on.

 

[Reg Braithwaite]

It's great seeing fellow divers thinking and wondering....but it would appear you have stepped beyond your understanding of decompression diving with the above example,,,,I might recommend the appropriate training, the internet and this forum is not the correct place for such advanced advise or training.

Thanks, I think I was quite explicit in saying that I was choosing the example schedule somewhat randomly. I considered calculating an actual schedule, however quite honestly I consider the idea of diving on air to 200' wrong, and printing a schedule in a a forum like this presents many problems. My choice was to state explicitly that it was a wrong schedule but close enough for the purpose of illustrating the point that a regular pony would not carry enough air to make for a satisfactory ascent from 200'.

If you feel my disclaimer was insufficient on that point, or that I was suggesting this is a schedule I would follow, then I apologize for not being sufficiently clear that I wasn't advising anyone to dive below 60' on air uhder any circumstances, much less 200' with a single tank and a bailout of any description.

The point was that a few people had answered the question of what mix goes in a pony bottle at 200' with a simple "don't!" and I wanted to give at least one reason why the answer is "don't."

 

[Rick Murchison]

Don't you mean Dihydrogen Monoxide??

A popular albeit not quite accurate moniker for hydrogen hydroxide.

Rick