Nitrox 28 in one tank and smooth classic air in the other

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Wetsuit 4 life

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Hello everyone,

Here's a question I have one tank my back gas with a Nitrox mix 28% and my pony with is now full of classic air, how would switching to my pony tank affect dive time and off gassing? Does this count as gas switching even if not being used for deco or extending bottom time? Is there any way to make this work or should I leave the pony tank at home this weekend?

Thanks

dave
 
Switching from EAN28 to air will increase your ongassing at depth, and slow your offgassing as you ascend. There's no bonus of any sort to this switch.

If your pony is a bail out bottle, and you're within the no-stop limits for your dive, then there's no real problem. You'd switch and immediately ascend just as you would on nitrox. I'd probably prolong my SI if I were forced to do this, but since being forced to do this would require me to have a significant problem while under, it's likely I'd be spending the SI fixing whatever broke.
 
Hello everyone,

Here's a question I have one tank my back gas with a Nitrox mix 28% and my pony with is now full of classic air, how would switching to my pony tank affect dive time and off gassing? Does this count as gas switching even if not being used for deco or extending bottom time? Is there any way to make this work or should I leave the pony tank at home this weekend?

Thanks

dave

I dive all kinds of mixes in my primary tank and I ONLY put air in my pony. The pony is for bail out from depth... 28 % or 21%...it ain't gonna make any difference if you use it for an ascent in an emergency...
 
Hello everyone,

Here's a question I have one tank my back gas with a Nitrox mix 28% and my pony with is now full of classic air, how would switching to my pony tank affect dive time and off gassing? Does this count as gas switching even if not being used for deco or extending bottom time? Is there any way to make this work or should I leave the pony tank at home this weekend?

Thanks

dave

You would be ongassing more nitrogen on air (EAN21) . . . but since you only swap to your pony in case of emergency, you won't be on it very long, right?
 
If you switch to your pony you should be turning your dive anyway. However, I still would switch my dive computer to the New gas (21). If you do not have a multi gas computer then I would add a few extra minutes to your safety stop just to be on the safe side.
 
If you switch to your pony you should be turning your dive anyway. However, I still would switch my dive computer to the New gas (21). If you do not have a multi gas computer then I would add a few extra minutes to your safety stop just to be on the safe side.

Seriously, the guy has an emergency and is on his way up and you want him to geek out on his computer? :shakehead::rofl3::rofl3:
 
1. Bring the pony bottle.
2. Set the computer to EAN 21 but do remember the MOD for EAN 28.
3. Set the computer to EAN 28 and if you do need the pony for bail out, spend extra time at 9 and 6m as someone had already suggested.
4. Refill your pony with EAN 28.
 
If you carry a pony bottle as an emergency backup only, why would you care what mix is in it? At the point of using an emergency pony the alternative would probably be a CESA and an orderly withdrawal is prefferable. I would plan on holding enough air in reserve, even if I had to blow off the safety stop, to insure I have air to deal with any issues I might foresee on the surface. Once I get to the surface I don't want to go right back down.

Dropping weights and oraly inflating a BC and are easy, but try it after an emergency when you are on the knife edge of panic, have the adreniline shakes, and it dosen't go as easily as planned. It's not just getting to the surface, the object is staying on the surface. Learned that back in '64.



Bob
--------------------------------------
In case anyone missed it, while still far better than drowning, having to do a CESA means you have violated two main rules of safety on the same dive: OOA (Out Of Air) and OOB (Out Of Buddy). It's time to re-evaluate your practices before you find yourself OOL (Out of Luck) and seriously injured or dead. NetDoc
 
Wetsuit 4 life:6274573:
Hello everyone,

Here's a question I have one tank my back gas with a Nitrox mix 28% and my pony with is now full of classic air, how would switching to my pony tank affect dive time and off gassing? Does this count as gas switching even if not being used for deco or extending bottom time? Is there any way to make this work or should I leave the pony tank at home this weekend?

Thanks

dave

Switching from 28% to 21% is going to give you less no deco time and is not going to help with off gassing. As long as your staying well within the recreational limits you should be fine. It does count as a gas switch but it is only going to be helpful by extending bottom time at a shallower depth. If your trying to help off gas you need to switch to the higher O2 content toward the latter shallower part of the dive. Take an advance nitrox class and you will learn all about this.
 
Seriously, the guy has an emergency and is on his way up and you want him to geek out on his computer? :shakehead::rofl3::rofl3:

I guess it depends on what an "emergency" is.
Once the diver dealt with their "emergency" by switching to their pony bottle, they would be able to calmly ascend and do a safety stop if they chose to.
They should have time to calmly switch the gas on their computer if they chose to.
It might not be necessary since they are aborting the dive......but they should have enough time.

-Mitch
 
https://www.shearwater.com/products/teric/

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