Should I get a Spare Air?

[WJL]

Rather than a Spare Air, I would like to get my hands on that harmonica-sized gadget that James Bond uses to breathe underwater. It seems to be some sort of rebreaher. You could stow it in a pocket and never have to worry again.

 

[Diver0001]

Lawman once bubbled...
My dive partner has a Spare Air he was
given in the early 90s when he was instructing.
I can use it if I want. HOWEVER, nobody on
the board seems to think much of them.
I'd like some technical opinions on whether
I should use it.

Also, what do you think about pony
bottles? Cost? Weight? Clumsy?

I'm just looking for some enlightened
opinions.

They (spare air) are terribly undersized. A 3 litre (19cf) pony is a better option if you really need a totally redundant air supply for bailout. Personally I use a Y valve and redundant 1st stages that I can shut down independently. If I were to dive solo (which I don't) then I'd consider a pony as an option.

R..

 

[MikeS]

Lawman once bubbled...
I'd like some technical opinions on whether
I should use it.

I think that you should defiantly use it, the question is what for, paperweight comes to mind! Or maybe you can get an adaptor the will allow you to blow the dust out of keyboards with it.

But seriously, I think you are going about it backwards. Rather than figuring out what you can do with it you should figure out the requirement and then calculate what you need. And then more importantly test it.

For example, I dive with a pony as a “bailout bottle” on dives over 60 feet. I only dive with buddies I trust but s**t happens and there is nothing like knowing that I have enough air in a totally independent SCUBA to get me safely to the surface. I don’t think that a controlled OOA ascent from below 60 feet is practical. So I went about trying to figure out the best size pony to use as a “bailout bottle” based on wreck diving off NC to 120 fsw, the worst-case example. First off I had to listen to the well meaning but impractical advice that I should get doubles or use H-valves and discard it. Than someone with much more experience than I suggested that I calculate how much air it would take based on my scenario. I did so and as a result got a 30 cf pony that I stage sling.

The calculation goes something like this:

SAC 1.0 cfm

13.9 cf - 120 fsw 3 min to figure out problem or float surface marker and start ascent
10.7 cf - Ascent from 120 fsw to 15 fsw at 30 fsw/min
4.4 cf - 15 min safety stop at 15 fsw
0.6 cf - Ascent from 15 fsw to surface at 30 fsw/min

29.5 cf Total

A SAC of 1.0 is not very high under a stressful and/or task loaded OOA situation. I tested it in the quarry from 80 feet and it more or less tracked. In a real life situation though I would not dilly-dally and spend three minutes at depth unless I absolutely had to.

Mike

 

[neil]

Besides all the other advice and opinions you are getting, IMO the Spare Air is a piece of junk. I used to work in a shop where we sold, repaired and overhauled them. It's a junky, finicky little single stage regulator that I would not rely on to save my life. If you want something really small, get a 6 cu. ft. bottle and put a real regulator on it.

 

[Northeastwrecks]

But if you want something that will actually get you out of a deep water jam, get an AL40. Sling it on your left side with a stage rigging kit.

You will need to be in seriously deep doo-doo before that won't get you out of a jam.

 

[Lawman]

Im convinced. I'm going to a small
pony bottle. With EAN 36 or 40
if I had to go up a little fast it might'
help ward off some DCI.

 

[MikeS]

Lawman once bubbled...
Im convinced. I'm going to a small
pony bottle. With EAN 36 or 40
if I had to go up a little fast it might'
help ward off some DCI.

My philosophy is that the P02 of the gas from the bailout bottle should not exceed 1.5 at the maximum depth. Based on the TDI table EAN 30 has a MOD of 132 fsw with a P02 of 1.5. Incidentally EAN 30 is typically banked at North Carolina dive operators.

To my mind the ability to use the gas at any depth without worrying about O2 toxicity outweighs and potential DCI benefit of mix with higher O2 content. If the bailout bottle is sized correctly there is no reason you should have to go up “a little fast.”

I typically keep the pony filled with EAN30. If the floor was below 132 fsw I would reduce the 02.

Mike

 

[Northeastwrecks]

MikeS once bubbled...


My philosophy is that the P02 of the gas from the bailout bottle should not exceed 1.5 at the maximum depth. Based on the TDI table EAN 30 has a MOD of 132 fsw with a P02 of 1.5. Incidentally EAN 30 is typically banked at North Carolina dive operators.

To my mind the ability to use the gas at any depth without worrying about O2 toxicity outweighs and potential DCI benefit of mix with higher O2 content. If the bailout bottle is sized correctly there is no reason you should have to go up “a little fast.”

I typically keep the pony filled with EAN30. If the floor was below 132 fsw I would reduce the 02.

Mike

Absolutely. It will decrease the redundancy you're seeking if you can't safely use the bottle at depth. Simply use a bottle that is big enough for you to figure out the problem, react, ascend normally and do the appropriate hangs.

Even the AL40 I mentioned earlier is not that heavy once you're in the water.

Of course, if you're doing shallow dives, then you would be fine with higher O2 mixes. What types of depth are we talking about?

 

[Lawman]

my thinking was this: Great Lakes wrecks are
generally w/in 100-110. EAN 36 is what my group
uses almost exclusively. MOD for EAN 36 is 111'.
If I have an OOA situation I will be going up and
even if below the MOD for that nitrox it would
only be for a matter of seconds. Since the 111'
foot MOD gives you a PO2 of 1.4 it would be
safe to have 36 or 40 for the few seconds
it would be necessary to head up.
It might help to throw off some nitrogen
on the way up as well.

Does that make sense, or am I missing
something here?

 

[Lawman]

what do you guys think of the tank
brackets to hold a pony bottle? How
do the effect balance? How about
hose configuration? [OK, let me have
it about a 7' hose!]. I trust your opinions
more than someone selling me something
at a LDS.