The smallest pony bottle (extra air source)

[NorthWoodsDiver]

if travel is an issue, just call the dive op ahead and rent an aluminum 19/30/40 and bring the 1/2 to 1lb of hardware necessary to use the tank and the reg setup.

to keep weight down for travel look into using a button gauge on the first stage and use just simple stage hardware to sling the bottles.

If you call a week or 2 before traveling any dive op (in popular dive destinations) should be able to arrange for a sling bottle though you may end up with an odd size or a steel rebreather bottle or something with a DIN fitting so the best bet is to call ahead and plan accordingly.

 

[Kevrumbo]

19 cuft pony recommended . . .prep, assemble and sling it like like a deco bottle.

 

[hmb]

Why is the size such a concern? Are you planning on taking it in checked luggage?

At a SAC rate of 1.0 (not unheard of in an emergency situation), a 4 c.f. bottle will last about 2 min at 30 feet (10 meters). That's not a lot of time to sort through an emergency that may come up and make a safe ascent. It's even less time if you decide to dive deeper than 10 meters.
...

In fact, I'm considering (completely theoretical) situation of emergency escape from a confined space which is rapidly filling with water. When 1-2 minutes (air in my lungs) might be not enough to find a way out. So, would be nice to have some extra air source. But this thing should be light? small and easy to use. Depth is not an issue at this point, really. Maybe, there something which is already part of a standard survival gear?
Well, I remember I'd seen once something of cigar size in one of the James Bond movies.

 

[NudeDiver]

Size is an issue if you travel because bottles take space and weight - both are at a premium in the "one free checked bag" universe in which we now live. If you CHECK the bag, weight is a real issue. But if you carry the bag on, most of the time it is not. So, there is some advantage to carrying the bottle on, rather than checking it. A 19cf is the biggest you can fit in a standard sized carry-on approved bag. By carrying it on, you can put more stuff in the checked bag.

Depending on some dive shop somewhere to have you covered with a pony that may or may not be there is not something everyone wants to do. Add in the per day rental costs for a pony, and it becomes even less attractive.

 

[LeadTurn_SD]

In fact, I'm considering (completely theoretical) situation of emergency escape from a confined space which is rapidly filling with water. When 1-2 minutes (air in my lungs) might be not enough to find a way out. So, would be nice to have some extra air source. But this thing should be light? small and easy to use. Depth is not an issue at this point, really. Maybe, there something which is already part of a standard survival gear?
Well, I remember I'd seen once something of cigar size in one of the James Bond movies.

I think that the scenario you've outlined above was what the Spare Air was originally designed for (allow pilots to escape from ditched & sinking Navy choppers?). If you are talking about a non-scuba, very shallow underwater escape that requires just a minute or two to complete, then yeah (and I can't believe I'm recommending this ) a Spare Air might be what you are looking for.

For diving, then you need a much larger capacity as others have already mentioned.

Best Wishes.

 

[Kevrumbo]

I think what hmb was referring to as well (the James Bond cigar shaped rebreather in Thunderball?) --was actually called the EOBA (Enriched Oxygen Breathing Apparatus) Rebreather. Introduced in Japan in the early nineties, max depth was 5meters with a gas duration of 10min: it never caught on or made the market here in the US . . .today's Spare Air integrated open circuit unit & bottle could perform the same survival function (enough air supply to find your way out of a capsized liveaboard before entirely sinking perhaps?), at a much less expensive cost & upkeep, and much more quicker to deploy.

 

[mangrovejack]

The other James Bond movie where a "breathing aparatus" of some kind featured was one where Pierce Brosnan played James Bond...can't remember the name though (Tomorrow Never Dies?).

 

[TGreene]

-- post removed because I found my answer --

-Tim

 

[halocline]

I have a 19CF pony..... It is 25% of the air in an AL80.

A buddy of mine has a 13CF. It is approx 1/8 the size of an AL80..

Unless I'm missing something this can't be right. Are all cylinders the same pressure? If so, how could 13cf be one half the size of 19cf?

I calculate that the 19cf pony is about 23% and the 13ft is about 16%. That's based on 80 cf capacity for the AL80, even though we know it only holds 77cf. I just assumed that the pony bottles also hold slightly less than their advertised size.

To put it in practical terms, the 19ft pony gives you about 690 PSI's worth of air in an AL80 and the 13ft gives you 480 PSI. Maybe a little more if the pony bottles are closer to their advertised volume than the AL80.

This is, of course, assuming I haven't totally forgotten how to calculate pressure vs. volume.

Assuming you're diving at recreational depth, with a buddy, staying out of mandatory deco, and not doing really stupid things, the 13ft pony "should" be plenty of gas to get you to the surface.

 

[Bretagus]

I just did these calculations yesterday. So, lets assume a worst case scenario of a catastrophic gear failure that catches you off-guard. With adrenaline rushing, you start breathing 1.5Ft^3/min. After taking 1 minute to alert your buddy and assess the situation, the gas required for just you to safely ascend (1ft/sec) to your 3min, 15ft safety stop, and then slowly ascend (0.5ft/sec) to the surface is as follows:

Depth (ft) Air (Ft^3)
40 6.2
50 7.0
60 7.8
70 8.8
80 9.9
90 11.1
100 12.4
110 13.8
120 15.4
130 17.0

All numbers come from the basic formula SAC*ATA*Time = Air consumed
Specifically, its the sum of all the equations below:

1 minute assessment = SAC*[(depth + 33)/33]*1
Ascent to 15ft at 1ft/sec = SAC*[((depth-15)/2)+depth+33)/33]*[(depth-15)/60]
Safety stop = SAC*[(15+33)/33]*3
Final Ascent = SAC * [(15/2+33)/33]*0.5

From my analysis, I wouldn't buy anything less than a 19ft^3 tank, presuming it was a bailout bottle for a single person's use. Also note that a 6ft^3 "pony" is garbage beyond 30ft.

Let me know if my equations look funky.
-Brett