Diving Nitrox with a pony bottle - theoretical
- Thread starter Ready4Launch
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
Keep in mind I'm not a tech diver, and am in the same experience bracket as you.... But from my research tech diving generally involves situations where immediate access to the surface isn't an option (due to deco obligations or physical overheads, or both). As such, they dive redundant air sources with the ability to isolate malfunctions (like doubles with an isolator manifold). They also gas plan with reserves according to the situation. A stage bottle is additional gas that is part of the plan (and may be a mix for specific portions of the dive).
For recreational NDL diving, I have a 19cf pony. It is effectively a buddy that never abandons me! I sling it on the front of my harness, and if I had to use it it's no different than OOA with a buddy (keep calm, establish an air supply, controlled termination of the dive). In an OOA situation, and you were on nitrox, would you refuse the alternate from someone on plain air?
On a side note, I suspect that the term "stage bottle" may originate from staging them in a physical location ahead of time. But I'm probably wrong!
For recreational NDL diving, I have a 19cf pony. It is effectively a buddy that never abandons me! I sling it on the front of my harness, and if I had to use it it's no different than OOA with a buddy (keep calm, establish an air supply, controlled termination of the dive). In an OOA situation, and you were on nitrox, would you refuse the alternate from someone on plain air?
On a side note, I suspect that the term "stage bottle" may originate from staging them in a physical location ahead of time. But I'm probably wrong!
You refuse options in the order of urgency, I suppose.
If you have a pony with Nitrox, you wouldn't refuse it, but if you only had access to air, you wouldn't refuse it, and so on.
As for the dive plan, I guess it's irrelevant to think in terms of "reserve/emergency".
You should only think in terms of redundancy.
If system 1 fails, do you have a complete system 2 to work off of?
You abort the dive when you have no redundancy.
In NDL diving, it is less urgent, because theoretically you can just surface whenever you want.
In a decompression situation, you'll have to surface based on the options listed in order of urgency...in some cases getting the bends and relying on rescue may be more preferable to blacking out and drowning.
But, to summarize, I think it's just too vague to think of having a "backup" like a pony botle.
It's convenient to have a pony bottle, but it works because in an NDL situation you don't need nearly the same reserves of air/mixed that you need for a decompression scenario.
If you have a pony with Nitrox, you wouldn't refuse it, but if you only had access to air, you wouldn't refuse it, and so on.
As for the dive plan, I guess it's irrelevant to think in terms of "reserve/emergency".
You should only think in terms of redundancy.
If system 1 fails, do you have a complete system 2 to work off of?
You abort the dive when you have no redundancy.
In NDL diving, it is less urgent, because theoretically you can just surface whenever you want.
In a decompression situation, you'll have to surface based on the options listed in order of urgency...in some cases getting the bends and relying on rescue may be more preferable to blacking out and drowning.
But, to summarize, I think it's just too vague to think of having a "backup" like a pony botle.
It's convenient to have a pony bottle, but it works because in an NDL situation you don't need nearly the same reserves of air/mixed that you need for a decompression scenario.
The only part of what he said that I'm being confused by is the source of redundancy in case of failure of the working gas supply.
I get the idea that a bottle may be called staged, and may actually be staged.
But it sounds like pony bottles (19cf as example) are insufficient to be a redundancy in case of emergency.
So do you just double-up on everything for decompression dives?
If you need 80cf of gas for a dive, now you carry 160cf?
A pony (as a pure emergency air source) is almost exclusively a recreational diving tool. In the tech realm, gas planning is much more complex and you are right, a pony is insufficient for their needs.
One variation of gas planning is the rule of thirds. One third there, one third back, one third in reserve. With doubles on an isolator, if one post fails at the worst time (turn point) each of the two tanks is 2/3 full... Isolate, and you still have gas to get back. Or buddy has total catastrophic gas loss, he gets your long hose, you're "reserve" was equal to worst case return needs, so you both still have gas to get back.
This is oversimplified examples... I don't have sufficient training to go further with that.
For my non-overhead NDL diving, my 19 is actually overkill.... For tech it would be laughably insufficient.
Thanks... Please tell me though if I over step my knowledge base. I certainly don't want to put out wrong info!
The valve on your pony should only be open if you're breathing from it, so having a free flowing regulator seems unlikely to me.
Not everyone agrees with having the valve closed. What problem is caused by having a slung pony with the valve on? It's an emergency supply....why delay its availability?
Similar threads
