Why Don't you Have a Pony yet?...or ever

[Cacia]

mmmmm. yea, I feel better on Nitrox dives...so I would just use this at my last deco stp to blow out the nitrogen with the increased gradient .5 of O2?

I would love to be less tired. After I do two dives on air, I need to sleep. So, it would need to be a designated tank, yes? You could not switch back and forth.

I think it would be tough for me to get those fills here. Or could any shop that does Nitrox just dial up the percentage?

 

[grazie42]

I guess it depends...
If they do PP-fills then it would be no problem...(which would be my guess). If they do PP-fills then you need a designated tank anyway because they´ll get the mix by putting in pure O2 first and then adding air to get the percentage you want...as long as you fill air from a "clean source" you can choose whatever eanx mix you want (including air)...also ean50 can be breathed down to 60ft without issue so depending on how often you want to refill your stage/pony you could switch even deeper...and for short exposures, even deeper, which is why IMO you could still use it as a pony should **** happen...

If they use a membrane-system then 40% is max (usually a fill of eanx is the same price as air on these)...then you can use whatever tank you want as there is never pure O2 in your system...of course it would propably make more sense to just dive ean32 or something in your main tank if that was the case...

I´ve personally slung a 40cft with 50% (when singletank diving) and that would be my preference...Doing some calculations on gas needed to get back from f´ups and the fact that I use it for decodiving made that the best choice for me...but as always YMMV

Most of what I´ve written about nitrox is taught in any good nitrox class....don´t anyone (else?) try this at home...disclaimer yada, yada, yada...

 

[Fun Diver]

Catherine...
Another benefit is that you could fill your pony with ean50 (or 100) and come up from the deeper dives "cleaner"/faster and feeling better afterwards...if you think about using it for that a 19 (or may I suggest a 30) would be a better choice...

Maybe it´s not much of a factor in Hawaii but here I notice it when I do safetystop with ean50 instead of air...maybe its just placebo but who cares? If I feel better, I feel better...

I wouldn't do that. Stick with air in a pony, that's standard practise.

For one thing a pony is considered a bail out, carrying anything richer than the mix in the primary tank means it has an MOD shallower than your primary tank allows. That defeats the purpose of a bail-out.

But secondly, what is suggested here is no longer recreational diving.. mixed gas dive planning is technical diving (and EAN mix above 40 is beyond recreational nitrox). You just shouldn't do this without technical training. The risk of oxygen toxicity and death from accidently breathing off a "rich" pony mix at depth is way too high IMO just for the perceived thought you'll "feel better" after a dive.

 

[grazie42]

I wouldn't do that. Stick with air in a pony, that's standard practise.

For one thing a pony is considered a bail out, carrying anything richer than the mix in the primary tank means it has an MOD shallower than your primary tank allows. That defeats the purpose of a bail-out.

But secondly, what is suggested here is no longer recreational diving.. mixed gas dive planning is technical diving (and EAN mix above 40 is beyond recreational nitrox). You just shouldn't do this without technical training. The risk of oxygen toxicity and death from accidently breathing off a "rich" pony mix at depth is way too high IMO just for the perceived thought you'll "feel better" after a dive

First...I realize you propably hadn´t read my latest post when you posted this but I still think some of what you posted needs to be adressed...

First..."standard practice" has IMO pretty much gone out the window a long time ago...particularly when you´ve read some of the OP´s previous posts

While the mod for 50% is shallower (according to rec agency standards) most "technical courses" teach decompression @ 1,6 pO2...we could have a long and drawn out discussion about pO2´s but lets not...

Catherine is nitrox certified and should know about all the points you made...whatever choice she makes will be hers after having weighed the risks/benefits of each solution which is the way all choices in diving should be made...

 

[Fun Diver]

First...I realize you propably hadn´t read my latest post when you posted this but I still think some of what you posted needs to be adressed...

First..."standard practice" has IMO pretty much gone out the window a long time ago...particularly when you´ve read some of the OP´s previous posts

While the mod for 50% is shallower (according to rec agency standards) most "technical courses" teach decompression @ 1,6 pO2...we could have a long and drawn out discussion about pO2´s but lets not...

Catherine is nitrox certified and should know about all the points you made...whatever choice she makes will be hers after having weighed the risks/benefits of each solution which is the way all choices in diving should be made...

fair enough, this board is just about hearing and speaking opinions.. I agree it's up to everyone to do what they want with what they read. I wouldn't say I haven't been tempted by the thought to carry a rich mix in the pony to help with off-gassing, but I weighed in the cons of that approach and personally decided it wasn't a great idea. The instructor I am working with from TDI advocates 1.4 pO2 for dive planning to allow room for contingency, but I'm sure the suggested practice will vary from instructor and agency.

 

[grazie42]

Actually, I think that´s what most (all?) agencies teach...I took nitrox with ANDI and trimix courses with IANTD and that´s what was in the material...and it is "best practice"...

I´m just saying that if I was OOA below the mod of whatever mix I had in my pony, I´d still breath it and still take my time making my way up the watercolumn...For me, I´d rather risk a few minutes at high pO2´s should **** happen and have the benefit of good off-gasing on all the other dives than the other way around...It´s only about 3 mins @ 9mtrs/min from 150ft to MOD of 50%...

I only dive that way on WW-trips and on dives where there´s no planned deco...which is what I´ve gathered the OP does as well...Context is a big part of finding the best solution to a problem...

By the way...I would suggest "slinging it" like a decobottle...that way you can keep an eye on it so that you´re sure there´s gas in the pony for when you need it and that you can turn the valve...DandyDon had a "popular" thread a while back about how "uncomfortable" it is to need the gas in your pony and find that there´s no gas in it...

 

[Fun Diver]

Actually, I think that´s what most (all?) agencies teach...I took nitrox with ANDI and trimix courses with IANTD and that´s what was in the material...and it is "best practice"...

I'm not arguing, just saying my TDI instructor advocates planning to 1.4. Well, at least he did a month ago..

I´m just saying that if I was OOA below the mod of whatever mix I had in my pony, I´d still breath it and still take my time making my way up the watercolumn...For me, I´d rather risk a few minutes at high pO2´s should **** happen and have the benefit of good off-gasing on all the other dives than the other way around...It´s only about 3 mins @ 9mtrs/min from 150ft to MOD of 50%...

If that's all I had, being OOA.. I'd breath it too! I've heard the suggestion (haven't tried it) you can take 1 or 2 breathes off just about anything and be ok. Hopefully one is ascending at that point to a safer depth for the gas. But I personally wouldn't make it my plan with what I brought as "bail out" gas. If I wanted to switch gas to a richer mix during ascent/deco, I'd bring another (well-marked) tank.. slung on the other side of course

 

[grazie42]

I´m not arguing either...I´m agreeing with YOU...pO2 of 1,4 is the standard

If that's all I had, being OOA.. I'd breath it too! I've heard the suggestion (haven't tried it) you can take 1 or 2 breathes off just about anything and be ok. Hopefully one is ascending at that point to a safer depth for the gas. But I personally wouldn't make it my plan with what I brought as "bail out" gas. If I wanted to switch gas to a richer mix during ascent/deco, I'd bring another (well-marked) tank.. slung on the other side of course

What I´ve heard (from people who´ve tried, repeatedly) is that it takes "a few minutes" for the body to "catch on" to what you´re breathing and if you´re "back in the green" by then you´ll be ok...also chambers use pO2´s of 2 and above for treatments....now granted the chamber is not the ocean but...

I guess it depends on how much time and how far below 60ft you´re planning to do start with...if you´re planning for a longer stay I´d say manifolded doubles are the way to go...like I said before...it´s all about context...

 

[dumpsterDiver]

Suggesting that Catherine use a "hot" deco mix in a pony is plain stupid. That will only increase the chance of her getting killed, not improve her safety in an emergency.

The pony is for an emergency ascent and redundancy. If you want to carry a THIRD bottle of deco gas, that is fine, but that is not what she asked about!

I often carry 100% oxygen in a sling bottle for deep dives, but I still have my pony filled with air. (In other words, I'm taking 3 tanks and this is not what she is asking about)

The 13 cuft pony will have a negative bouyancy of maybe 3 lbs, but it depends on the size of the first stage.

 

[ianr33]

Your weighting should be he same as it would be with no pony. If you reduce your weight,have an OOA on your backgas and then use up most of the gas in your pony on ascent you will be underweighted which will only make a bad situation worse. Would also mean you could not hand it off to another diver.

Using a high O2 mix in a bailout bottle is just dumb. You can not use it on the bottom and without the training you wont know the dangers. You probably wont even be able to get it filled.

If you decide on a pony,sling it on your front (About a gazillion threads as to why)