Different mixes and pony bottles

[diveandclimb]

To clarify: For me deep is anything past 60'. For the most part that means wreck dives in the 80-100' range.

Having listened to all the argument I am still unclear on one thing: It seems like the consensus is air in the pony which is fine but if I have a single gas computer and tell it I am going to be using EAN32 (for example) and then need to bail out on air, won't it speed up my safety stop time because it thinks I'm still on EAN and then I could risk getting bent? Thanks.

 

[texdiveguy]

To clarify: For me deep is anything past 60'. For the most part that means wreck dives in the 80-100' range.

Having listened to all the argument I am still unclear on one thing: It seems like the consensus is air in the pony which is fine but if I have a single gas computer and tell it I am going to be using EAN32 (for example) and then need to bail out on air, won't it speed up my safety stop time because it thinks I'm still on EAN and then I could risk getting bent? Thanks.

The risks of getting bent are low to begin with in terms of the number of dives made against the actual numbers of reported DCS....very low.

As a general statement, no you will not get bent from going from a back gas of EAN32 to a pony bottle of contingency AIR on your OOG ascent from NDL depths including recommended safety stops.

Make your ascent slow as always, breathing normally, and apply safety stops based on the available gas in your pony bottle.

 

[HowardE]

Having listened to all the argument I am still unclear on one thing: It seems like the consensus is air in the pony which is fine but if I have a single gas computer and tell it I am going to be using EAN32 (for example) and then need to bail out on air, won't it speed up my safety stop time because it thinks I'm still on EAN and then I could risk getting bent? Thanks.

Your "safety stop" which is basically a 3-5 minute deco stop... won't be different... You were already planning on doing it.... Right?

If you don't "go into deco" on your computer, or plan a NDL dive... the air vs nitrox won't make a difference as far as your time, and your computer is concerned... since - once you did bail out to the pony, your bottom segment of the dive would be over, and you'd be starting your ascent.

 

[tomboyy]

To clarify: For me deep is anything past 60'. For the most part that means wreck dives in the 80-100' range.

Having listened to all the argument I am still unclear on one thing: It seems like the consensus is air in the pony which is fine but if I have a single gas computer and tell it I am going to be using EAN32 (for example) and then need to bail out on air, won't it speed up my safety stop time because it thinks I'm still on EAN and then I could risk getting bent? Thanks.

You say your diving 80-100... if you have to use your bail out your not going to need to switch anything ... you ASCEND at a safe pace ( your computer will tell if your to fast) STOP at 15 feet your computer will say if your at 15 feet STAY there for 3 mins minimum.. longer if you can. PERIOD.

If your computer doesn't tell you this basic information get a new one. Get a Buddy! Read ! Dive !

 

[HowardE]

I should also add... that I would have no problem putting 32% nitrox in my bottle, if I was in this scenario (but I don't dive with a pony bottle)... Since 32% is just fine for ANY dive within the recreational dive limits.

 

[tomboyy]

Your right Howard. I just said it this way cause the OP Is not even Nitrox certified yet and from his level of question the more simplified this is the better

 

[Lucy's Diver]

If its a true pony (emergency only) air fill it. You could bounce deeper in a real bad emergency (yes I know bad, but stuff happens, e.g. unconscious buddy drops below EAN limt), its cheaper, and if you bail on the air just head up and extend the safety stop - though at that point I would sit out the rest of the day.

I sometimes fill a pony with my back gas - when I know I have a hard bottom within the EAN limit, and I also get all the free EAN fills I want.

 

[DwayneJ]

I recommend air. If you ever bail to your pony take a nice long safety stop.

I use air in my 30cf pony -

The act of opening the pony bottle valve purging regulator to test and clean quickly eats up a few cf per dive and if nitrox is not readily available, you will be forced to top up with air or perform a nitrox transfer from your main tank. When you do top up you will need to retest the mixture to document the revised nitrox mix and associated max depths at 1.4/1.6 PPO2. This implies you will have access to a gas analyzer.

There are good (expensive) full deco computers that you can program with your main and bailout setup that will provide accurate (deco) stop obligations if you choose your bailout bottle. Again every dive is a deco dive and these same computers will open your diving to the world of micro bubble stops. Check out the posting "PerroneFord changed my thinking, n maybe even saved my life.". On deeper dives of 105-114ft, my "recreational" dive computer would not have me perform micro bubble stops whereas My VR3 does. Certainly PerroneFord changed my thinking about dive planning within recreational limits. You certainly can perform micro bubble stops without a computer telling you to do so.

As an FYI, there is no reason why you could not calculate your safety stop obligations using various mixtures with various scenarios with dive planning software.