Preferred mix in a pony

[Jimmer]

Doesn't make a big difference, but I like practicing doing gas switches on my ascents and safety stops, and if I'm doing a practice gas switch, why not breathe a richer mix and get SOME advantage out of it?

How much difference does that make to your nitrogen loading?

 

[Thalassamania]

Air, except for some special cases where it is bottom mix.

 

[ianr33]

I've been going through the Advanced Nitrox book for a while, just haven't written the exam and got the card yet. Instructor doesn't have any problem with me using 50% since I'm in the middle of the course, but I don't use O2 or anything like that since I'm not doing deco, I just use it to help "clean up" a little on the safety stops, and to get used to gas switching for when I take my deco procedures course.

How do you mark your tank with 50% in it? Are you diving with people that know what the markings mean?

Not meaning to bust on you here but a tank of 50% in the wrong place/hands is dangerous as I am sure you know.

 

[Jimmer]

No worries, it's a fair question. I have a DiveRite "MOD 70" sleeve that I slip on when that is the case, since as I said I sometimes use air or something else. If it's something else other than air, it's marked appropriately with the mix and MOD. As for other people on the boat, I dive with a lot of the same people (small diving club) some of them are Nitrox certified and they understand what MOD 70 means, the other I just explain to them what it means and that it can't be breathed past that depth. Same way I explain to them how if I am diving with one of them, and we need to share air, they get the one in my mouth on the long hose and I take the one on my necklace.

How do you mark your tank with 50% in it? Are you diving with people that know what the markings mean?

Not meaning to bust on you here but a tank of 50% in the wrong place/hands is dangerous as I am sure you know.

 

[ianr33]

Fair enough. Sounds like you have your bases covered.
It is very easy to forget that your average diver will have no idea what MOD 70 means (no reason they should know)

 

[daniel f aleman]

Air. I use a pony as a bailout only.

 

[Jimmer]

I totally agree, most of the people I've met on boats are always pretty curious and happy to learn.

Fair enough. Sounds like you have your bases covered.
It is very easy to forget that your average diver will have no idea what MOD 70 means (no reason they should know)

 

[1_T_Submariner]

I think I was the guy that asked this question last (Maybe). There was alot of the same disscussion. I think the good points of filling it with 32 or 36 was that it made sense for offgassing at a safety stop and since it is a pony and NOT a stage if you switch to it when deep you would be ascending anyway.

Good question if I do say so myself.

 

[chrispete]

(Up front caveat:within recreational limits & in normal rec diving) In a perfect world I'd have a mix matching what's in my primary tank(s.) To me this would simplify everything invloved - if you are above MOD for your tank mix, you're above MOD for your pony mix, period. The tables/computer time are the same if you are breathing the same mix. At the point of failure, you don't have to weigh any options - you just grab the pony reg and breathe. Failing that I'd have a less potent mix or air, in which case _as long as you begin your ascent immediately_,_albiet controlled_ you are pretty much at the same N2 load that you were at with your mix and thus would be safe to proceed to the surface given that you were within your nitrox mix's NDL and that you took appropriate (best longer) safety stops on the way to the surface.

Any which way, I'd sit out the rest of the day's dives and calm my nerves...

 

[Mack Diver]

Lots of great commentary. Thanks to all that responded. I agree that a mix could be used for a staged / planned safety stop, but as an emergency backup, air makes simple work out of a bad situation.