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View Full Version : Is a Nitrox Pony Bottle overboard?



aaronle06
02-27-2010, 09:32
I was doing my AOW and Nitrox knowledge book studies this morning and it got me thinking...

Nitrox in a pony bottle? Overboard? Not Applicable? Useful? Possible?

UCFKnightDiver
02-27-2010, 09:43
depends how deep you're diving, if you are diving to 100 you obviously don't want a 40% or more mix in your pony bottle.

navyhmc
02-27-2010, 09:58
One school of thought is that if you carry a pony and you're back gas is nitrox, your pony should be the same nitrox%.

Remeber a pony should be a just in case back up. Not part of your gas plan for the dive. So it makes sense to have the same % in both.

jbres1
02-27-2010, 10:52
My pony gets filled with air most of the time, and gets topped off with whatever I am diving with when I need a top off.
Air will get you to the surface just as well as nitrox, and you can go deeper on air than nitrox.
If you end up using your pony for some reason or another most of the time you are done diving for the day ,so using air will not be your first concern.
Jim Breslin

comet24
02-27-2010, 12:07
When I dove with a pony it was mostly air. I wouldn't dump what's in it for a special fill. If you want to fill it with nitrox 32% will work for any rec. dive. At 130' your PPO is 1.58 and if your going to your pony you should be on your way up and decreasing you PPO. I wouldn't fill it with anything higher to prevent pushing an unsafe PPO if I had to bail out.

RogerAg
02-27-2010, 12:44
I use a 13 Cu. Ft. Pony that I always top off with my wife's full tank. So sometimes its Nitrox and sometimes Air.
During my safety stop, if there’s still a lot to see and my regular tank is nearly empty (the boat I usually dive from likes for me to have at least a few breaths of Air on the boat.) I will sip from the Pony. I know that at 15 or 20 ft. I can sip on my Pony for 12 mins. Though I don't stay at a safety stop that long.

So if I take air from the Pony, I simply top off from my wife's next tank. Did I mention that my wife can sip from a 80 for two hours if we let her.

All that said, I never really know how much Nitrox is in the Pony unless I am filling to a empty pony (my Pony is always empty and the valves are screwed off when travelling on a airplane), however I have never dived with more then 34% and since I dive Air most of the time, I know that the Pony has less then 43 % in it.

Sansho
03-02-2010, 21:19
I use air in my pony, even when diving Nitrox in the main tank. The pony is for emergency use only, and air works fine for that.

bassplayer
03-03-2010, 06:20
I asked my Instructor a similar question last week.

If you are diving Nitrox and run into an OOA (yea I know) situation, and use a buddies tank who is on air to get to the surface, does this end your diving for the day? He said the difference for that situation was so negligible as to have little affect on your dive profile.

So using that logic if you are using your pony for an emergency bail out only, then air should be ok.

NAUIWowee
03-03-2010, 08:08
Another consideration is cost at VIP time. Nitrox tanks have to be O2 cleaned each time their are VIP'ed, so your going to pay for a scrubbing each year.
I have two nitrox 80's and my pony was nitrox. After paying for this a couple of years, I decided to just let my pony be air. I decide its only for bail-out purposes and I'm going to be off-gassing on my way to the surface anyways, so I don't think the extra nitrogen is going to have much affect for that short a period of time.

ssmdive
03-03-2010, 10:02
I'd put air in it..... It is for emergency use only, and air is good to a much deeper depth.

So lets say you put 32% in it and your profile was 200 feet. You would need to dump the 32% to put air in it (or Mix).

LiteHedded
03-03-2010, 10:15
if you're going to use one of these things there's no reason to use anything other than air.

skdvr
03-03-2010, 11:16
I use air. Just using it to get to the surface. Air is good! No reason to pay to put nitrox in it. If you try to match your back gas all the time you will end up wasting money on gas in your pony.

Phil

CompuDude
03-03-2010, 16:44
Another consideration is cost at VIP time. Nitrox tanks have to be O2 cleaned each time their are VIP'ed, so your going to pay for a scrubbing each year.
I have two nitrox 80's and my pony was nitrox. After paying for this a couple of years, I decided to just let my pony be air. I decide its only for bail-out purposes and I'm going to be off-gassing on my way to the surface anyways, so I don't think the extra nitrogen is going to have much affect for that short a period of time.

Depends on how they're filling Nitrox. If they're PP blending, then yes, it would have to be o2 cleaned, which is pretty absurd. If they're using a membrane system, or premix, or you're just transfilling from another tank, there's no need to be o2 clean.

Personally, though, I would just use air. For NDL diving you're only going to be on a pony for the direct ascent time plus the safety stop (assuming your pony has enough gas for it), so 7 minutes of air vs. Nitrox isn't going to make much difference (especially if the last 3 min are at 15').

NAUIWowee
03-04-2010, 07:56
Another consideration is cost at VIP time. Nitrox tanks have to be O2 cleaned each time their are VIP'ed, so your going to pay for a scrubbing each year.
I have two nitrox 80's and my pony was nitrox. After paying for this a couple of years, I decided to just let my pony be air. I decide its only for bail-out purposes and I'm going to be off-gassing on my way to the surface anyways, so I don't think the extra nitrogen is going to have much affect for that short a period of time.

Depends on how they're filling Nitrox. If they're PP blending, then yes, it would have to be o2 cleaned, which is pretty absurd. If they're using a membrane system, or premix, or you're just transfilling from another tank, there's no need to be o2 clean.

Personally, though, I would just use air. For NDL diving you're only going to be on a pony for the direct ascent time plus the safety stop (assuming your pony has enough gas for it), so 7 minutes of air vs. Nitrox isn't going to make much difference (especially if the last 3 min are at 15').

My LDS does partial pressure blending, so my tanks have to be scrubbed annually. Which sucks, I know. I wish he would bank some pre-mix.

jugglematt
03-06-2010, 04:32
one of my dive buddys has a nitrox pony bottle

his idea is .
he does his dive on air no deco dives , and then does his safety stop on 40% or 50% nitrox ,
he has a pony for out of air situations , he is self sufficient , he has the nitrox for a safer dive , he fills and scrubs his own tanks , so cost is not a big factor.

im actually setting up a pony bottle and will be running it at 40% nitrox PP blended at home. so apart from test and scrubbing there is no increase in cost.

at the moment im doing all my dives on a 32% mix , and using air tables .
for an increased margin of safety.

i would also like to set up a small O2 bottle and O2 reg to have permanently stored on my boat for suspected DCS incidents or missed safety stops ect .
my theory is that if i dive enough its only a matter of time before myself/my buddy or a boat nearby has an incident

matty

mitsuguy
03-07-2010, 18:05
Another consideration is cost at VIP time. Nitrox tanks have to be O2 cleaned each time their are VIP'ed, so your going to pay for a scrubbing each year.

not necessarily... so long as the shop you are using isn't partial pressure blending, there is no need for O2 clean tanks... so, if they fill from banked nitrox, or if they fill from a continuous flow system, there is no need to O2 clean your tank...

edit: damn, CD beat me to it, and I didn't even see the second page!

mitsuguy
03-07-2010, 18:08
My LDS does partial pressure blending, so my tanks have to be scrubbed annually. Which sucks, I know. I wish he would bank some pre-mix.

we do partial pressure too... tell ya the truth, we don't do enough nitrox diving around here to justify anything more than the small investment needed for PP blending... your locale will determine whether it is worth the investment for alternate nitrox fill methods...

ianr33
03-08-2010, 06:44
im actually setting up a pony bottle and will be running it at 40% nitrox PP blended at home. so apart from test and scrubbing there is no increase in cost.


Whats the pO2 of 40% at 130 feet?

navyhmc
03-08-2010, 07:18
im actually setting up a pony bottle and will be running it at 40% nitrox PP blended at home. so apart from test and scrubbing there is no increase in cost.


Whats the pO2 of 40% at 130 feet?

Dangerous!!! 1.98 ATA

jugglematt
03-08-2010, 12:30
the p02 of a 40% mix is not an isssue for me at the moment as im limiting my diving depth to 20m for a while. if i find im doing deeper dives i can bring it back to 32% which will be ok for the deeper dives we do here.
if i have a PP blending setup at home why not use it ?

main thing i would like to set up a pony is for a bail out system .
Matt

navyhmc
03-08-2010, 12:58
the p02 of a 40% mix is not an isssue for me at the moment as im limiting my diving depth to 20m for a while. if i find im doing deeper dives i can bring it back to 32% which will be ok for the deeper dives we do here.
if i have a PP blending setup at home why not use it ?

main thing i would like to set up a pony is for a bail out system .
Matt

That's a plus for having a bail out at the same % as your back gas. You're not giong deeper than 1.4 ata (well, hopefully) so you're still good.:smiley20:

Code Name Cobra
04-08-2010, 14:23
I use a 28% mix for 130' plus dives and max out my pony at 40% in an emergency you will be accending and will not be at an unsafe depth long enough to build a toxicity in thoery. In a non emergency, I switch to my pony at 80' on my accent to help off gassing.

navyhmc
04-08-2010, 15:54
The only problem with that scenario Code is that "In Theory" you should not have a problem. I usually use the same mix in pony as back gas so I'm within a known safe ox-tox level. Will your set guarantee a o2 hit? No, but personally, I like to stay within knowns.

gNats
04-08-2010, 16:29
I'm surprised nobody talked about this angle/point yet.

OP: In AOW, a pony bottle should strictly be an emergency/redundant gas, and it should match your back gas.

I'm not going to be scuba Police here, but, technically, I think a lot of people would agree that if you are a recreational AOW diver, your back gas and pony gas should match because the pony tank is strictly to give you a redundancy, not as a gas switch.

Now, do some divers sip off their pony? Sure, but that's for the police to handle, not me.

When a diver's training goes beyond recreational diving, there is an Apprentice tec class. The apprentice tec class (PADI) does not allow you to go beyond the recreational depths, or do DECO diving, but it does teach you how to plan extended - no deco diving by switching gases throughout the dive.

So, if the back gas is air, and your pony bottle has 40% in it, you can extend your dive time by moving to the 40% bottle and reducing the amount of nitrogen you are absorbing.

Until you receive the special training on gas switching and changing regulators, you shouldn't do this on your own. I'm not the police here, but there is more to it than just changing regulators. you need to always make sure you don't breathe that higher O2 gas at a depth deeper than it is rated.

Your pony bottle is considered your dive-time gas, not redundant. So, you are also expected to dive doubles so you do have redundant back-gas.

CompuDude
04-08-2010, 17:59
I'm surprised nobody talked about this angle/point yet.

OP: In AOW, a pony bottle should strictly be an emergency/redundant gas, and it should match your back gas.

I'm not going to be scuba Police here, but, technically, I think a lot of people would agree that if you are a recreational AOW diver, your back gas and pony gas should match because the pony tank is strictly to give you a redundancy, not as a gas switch.

Now, do some divers sip off their pony? Sure, but that's for the police to handle, not me.

When a diver's training goes beyond recreational diving, there is an Apprentice tec class. The apprentice tec class (PADI) does not allow you to go beyond the recreational depths, or do DECO diving, but it does teach you how to plan extended - no deco diving by switching gases throughout the dive.

So, if the back gas is air, and your pony bottle has 40% in it, you can extend your dive time by moving to the 40% bottle and reducing the amount of nitrogen you are absorbing.

Until you receive the special training on gas switching and changing regulators, you shouldn't do this on your own. I'm not the police here, but there is more to it than just changing regulators. you need to always make sure you don't breathe that higher O2 gas at a depth deeper than it is rated.

Your pony bottle is considered your dive-time gas, not redundant. So, you are also expected to dive doubles so you do have redundant back-gas.

Sort of.

It should either match your back-gas, or be air. I suppose, an argument could be made for a lower percentage Nitrox being ok, but that's not something I would purposely aim for... I just wouldn't blink at it if 28% was in my pony and I had 32% (or higher) backgas (strictly as an example to illustrate the point).

For OW NDL diving, if you're on your pony, you're on your way up anyway. The time it takes to ascend directly from the maximum recreational depth should not really significantly affect your on/offgassing anyway, so if you're diving Nitrox and have air in your pony, that's fine.

I agree that using a pony as a gas switch for accelerated off-gassing is definitely outside the realm of recreational diving, and should not be practiced without significant extra training.

fire diver
04-09-2010, 07:19
I'm going to throw my 2 psi in on this debate.

As has been stated already, for all NDL dives, the pony is to be considered an emergency bailout gas only. In that measure, you should be carrying air in your bailout. Why? Because its a pain in the butt to have to change your pony gas mix to match your backgas every dive, or day, or outing. Air is always within PPO limits for your dives, and it doesnt cost extra to fill with plain air. Simplify your dive plan.

What I do recommend with your emergency reserve is using it every outing. Practice switching and ascending on it for your last dive of every trip (unless you live next to the ocean and dive almost daily ). The switch should be a routine and normal experience if you DO have a backgas emergency some day.

navyhmc
04-09-2010, 08:21
I use a 28% mix for 130' plus dives and max out my pony at 40% in an emergency you will be accending and will not be at an unsafe depth long enough to build a toxicity in thoery. In a non emergency, I switch to my pony at 80' on my accent to help off gassing.

One more thing on your 40% pony: at 130' your PaO2 is right at 2.0 ATA (1.98). Even if you're heading right up, depending on your previous dive Percent of Allowable Exposure loading, you definitely run a OX-tox risk. While my math is a little sketchy, and the formula I'm using is not entirely accurate, at 130', for 1 minute, your PAE for 40% is over 100% for a 24 hour period.

Grin
04-09-2010, 08:59
If your checking your ponies pressure before every dive, or diving it in the valve on mode (my preference), your going to need to top it off about every couple days diving. I do this with a crossfiller settup. Thus my pony ends up with a average of the the same mixes I dive. I usually crossfill my 13 pony with my main tanks full of 33-36 mix. And I usually crossfill my 19 pony with my tanks full of 32 or less. Whenever I suck a pony down, and decide to have the shop fill it, I just have them fill it with air. I wouldn't worry about the benefits of NITROX in the pony too much. I would be a little more concerend about breathing off it if the PO2 were way too high, even for a short period.

CompuDude
04-09-2010, 14:08
If your checking your ponies pressure before every dive, or diving it in the valve on mode (my preference), your going to need to top it off about every couple days diving. I do this with a crossfiller settup. Thus my pony ends up with a average of the the same mixes I dive. I usually crossfill my 13 pony with my main tanks full of 33-36 mix. And I usually crossfill my 19 pony with my tanks full of 32 or less. Whenever I suck a pony down, and decide to have the shop fill it, I just have them fill it with air. I wouldn't worry about the benefits of NITROX in the pony too much. I would be a little more concerend about breathing off it if the PO2 were way too high, even for a short period.

Agreed whole-heartedly. Sounds like a very reasonable procedure.

scubagirlj
04-09-2010, 19:57
deco bottle for higher percentage nitrox, pony/bailout bottle same as travel/bottom mix-that's what i was taught