Diving Nitrox with a pony bottle - theoretical

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Ready4Launch

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Say a dive is within nitrox dive depths but your pony bottle isn't nitrox and just air ... say you had to go to the pony from your nitrox main tank, would you expect to experience narcosis rapidly? What is the effect?

(Of course, it's better to have the pony filled with nitrox to begin with, but this is just a hypothetical.)
 
Oxygen's and nitrogen's narcosis level/degree are nowadays regarded to be very close to each other so there shouldn't be any significant change of narcotic effect when changing form nitrox to air.

If you would be using trimix that has helium in the gas mix the situation would be different as helium is far more less narcotic as oxygen or nitrogen. Of course at depths where you would need trimix gases changing to air would be problematic because of high ppo2 level, increased WOB and co2 retention due to gas density.
 
What he said. Depending on depth and size of your pony, you may have little to no time to sort a gas supply issue out on the bottom. Best to be heading up.
 
Using a pony bottle raises various considerations, but narcosis is not one of them (unless, as someone already mentioned, you were previously breathing a helium mix). Totally irrelevant.
 
Once you get a pony you'll understand. You don't take a pony to the dive shop for a fill. You plug it into whatever tank you're diving with a transfill whip, and therefore it gets whatever your main tank has. It doesn't have to be 02 cleaned in order to contain nitrox that's already mixed. 02 cleaning is really for doing partial pressure blending to make nitrox where you introduce 100% oxygen, then thin it out with air. In fact, I don't think pony bottles regularly get VIPped. You could probably even skip hydro if you wanted (I won't be doing that). Some dive shops who sell banked nitrox might insist on 02 cleaning, but that's just a money grab and has nothing to do with safety.

For the most part, my pony gets filled before the first dive of a trip. It only gets emptied if I need to get onto a plane, as you shouldn't actually be breathing from it unless you've screwed the pooch in a major way. However, I have used my pony to work on the bottom of my swimming pool since I only needed 5 minutes to screw in a new intake cover.

Since it's filled with whatever in your main tank, the specific contents require no extra consideration. Besides, even if it had 10% CO it's only for emergencies. I'd prefer 10% co to straight up drowning. At least you MIGHT live.
 
Oxygen is regarded today as being virtually as narcotic as nitrogen and nitrox is no longer promoted as a gas that reduces narcosis.

@Ready4Launch the above is most important. Since we consider O2 to be narcotic, and roughly equally to N2, then your question about narcosis changes is that it won't. You'll also likely have tunnel vision and what not from dealing with the situation but the gas change won't make it worse.
 
Once you get a pony you'll understand. You don't take a pony to the dive shop for a fill. You plug it into whatever tank you're diving with a transfill whip, and therefore it gets whatever your main tank has. It doesn't have to be 02 cleaned in order to contain nitrox that's already mixed. 02 cleaning is really for doing partial pressure blending to make nitrox where you introduce 100% oxygen, then thin it out with air. In fact, I don't think pony bottles regularly get VIPped. You could probably even skip hydro if you wanted (I won't be doing that). Some dive shops who sell banked nitrox might insist on 02 cleaning, but that's just a money grab and has nothing to do with safety.

For the most part, my pony gets filled before the first dive of a trip. It only gets emptied if I need to get onto a plane, as you shouldn't actually be breathing from it unless you've screwed the pooch in a major way. However, I have used my pony to work on the bottom of my swimming pool since I only needed 5 minutes to screw in a new intake cover.

Since it's filled with whatever in your main tank, the specific contents require no extra consideration. Besides, even if it had 10% CO it's only for emergencies. I'd prefer 10% co to straight up drowning. At least you MIGHT live.

Depends on your diving. Most of my diving is done by car not air. I do not want to fill it off the main tanks since that reduces the air in the main tanks and does not not add to the total air availalble. So I get it filled at LDS. If it happens to get low, say free flow, or after several dives, I will get it topped off when I get my nitrox fills. Top it off with air since cheaper and as noted if I am on the pony I am ending my dive.
 
Once you get a pony you'll understand. You don't take a pony to the dive shop for a fill. You plug it into whatever tank you're diving with a transfill whip, and therefore it gets whatever your main tank has.

I know people do this with the 'spare air', but I didn't know they do it with a pony bottle. Seems like filling a 20cf or 40cf pony bottle would leave you with half a primary tank.

I just bought a 20cf pony bottle (delivered to my Mom's place in Florida). It will be going straight to the LDS for assembly and fill. I'll never buy a whip for it.
 

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