Testing a Spare Air

[vjongene]

I was recently at my LDS enquiring about a pony bottle, explaining that I was planning to do more buddy-less diving to have time for leisurely photography. They suggested trying a Spare Air instead. To be clear, this is as a safety backstop for recreational dives no deeper that 20 m, and well within NDL. I have read the many negative comments on this forum about Spare Airs, and particularly the calculations showing that they would be useless in case one really runs out of air during a dive.
So I decided to actually see what happens when breathing from a Spare Air. No one would mistake this for even a cheapo reg, it takes some effort to suck air out of it, but it works. First test was at 4 m depth, finning vigorously to get back to my entry point. The air lasted for a little over 4 min, which my buddy found surprising given the small size of the bottle. Second test was switching air sources at 22 m depth and performing a standard ascent at about 10 m/min. Easily made it to 3.5 m depth (took 2 min), and had enough air left for about 1 min safety stop. I could have done a CESA from there if needed.
So from my POV this thing does what I expected it to do. If I should have an equipment failure or an OOA at 20 m or less, I can make it to the surface unharmed. I agree that if I should be panicking it may not last as long, but with >1000 dives under my belt I don't see this as a very likely scenario. I can clip it to by BCD where it is out of the way but easily grabbed, and under most OOA scenarios at <20 m depth it will allow me to get back to the surface. I hope that this will not trigger a flame war, thought I would share the experience.

 

[scubadada]

Hi @vjongene

You didn't say which model you were diving, I assume the 3 cf, they also make a 6 cf and a 1.7 cf.

This topic has been discussed many times on SB, the calculations are easy. I could just make it directly to the surface from 60 feet with a normal ascent at twice my average RMV with the 3 cf. I wanted enough gas to cover all my diving within recreational limits, so chose a 19 cf pony. Choosing a redundant gas source is an example of the right tool for the job.

 

[DandyDon]

the 3 cf, they also make a 6 cf and a 1.7 cf.

Isn't that 1.7cf a hoot? I wouldn't bother with smaller than 6cf. I've done a Cesa from 50-something feet, wasn't hard, but nothing else went wrong. Spare gas is always good, the more the better.

 

[abnfrog]

you forgot about bay watch ,...6cf lasted almost 30 min at any depth .......lol

 

[JackD342]

I was recently at my LDS enquiring about a pony bottle, explaining that I was planning to do more buddy-less diving to have time for leisurely photography. They suggested trying a Spare Air instead. To be clear, this is as a safety backstop for recreational dives no deeper that 20 m, and well within NDL. I have read the many negative comments on this forum about Spare Airs, and particularly the calculations showing that they would be useless in case one really runs out of air during a dive.
So I decided to actually see what happens when breathing from a Spare Air. No one would mistake this for even a cheapo reg, it takes some effort to suck air out of it, but it works. First test was at 4 m depth, finning vigorously to get back to my entry point. The air lasted for a little over 4 min, which my buddy found surprising given the small size of the bottle. Second test was switching air sources at 22 m depth and performing a standard ascent at about 10 m/min. Easily made it to 3.5 m depth (took 2 min), and had enough air left for about 1 min safety stop. I could have done a CESA from there if needed.
So from my POV this thing does what I expected it to do. If I should have an equipment failure or an OOA at 20 m or less, I can make it to the surface unharmed. I agree that if I should be panicking it may not last as long, but with >1000 dives under my belt I don't see this as a very likely scenario. I can clip it to by BCD where it is out of the way but easily grabbed, and under most OOA scenarios at <20 m depth it will allow me to get back to the surface. I hope that this will not trigger a flame war, thought I would share the experience.

Thanks for the detailed scenarios.
I never understand why so many folks hate on the Spare Air. As you said, it does what it says it does. Once you accept it is not a pony bottle, and is not a direct replacement for a pony bottle, you can focus on what it does do.

In fact, last year I switched from my 3cf bottle to a 1.7cf bottle. No, it is absolutely not as useful as the 3cf version. But since finding a place to clip the 1.7 is far easier and less intrusive than attaching the 3, I decided to opt for the smaller size that actually gets wet rather than stick with the larger, better size that pretty much stays dry at all times. Took me a while to realize that and accept it, rather than repeatedly vowing to change my behavior next time.

 

[scubadada]

Isn't that 1.7cf a hoot? I wouldn't bother with smaller than 6cf. I've done a Cesa from 50-something feet, wasn't hard, but nothing else went wrong. Spare gas is always good, the more the better.

I could not make a normal ascent from 130 feet at twice my average RMV with the 6 cf. At closer to my normal RMV I could. I use twice my average RMV for my emergency calculations.

 

[scubadada]

Hi @JackD342

In what situations do you see using your 1.7 cf Spare Air?

 

[JackD342]

Hi @JackD342

In what situations do you see using your 1.7 cf Spare Air?

I plan to never use it.
I don't dive tech requiring deco stops, and tend to stay above 80 feet choosing instead to maximize my bottom time. It is pretty unlikely that I will simply run out of air, so the most likely situation where I might find I need it would be if I had a catastrophic failure - a sudden loss of all air options from my cylinder. Even if it gets me only to about 30 feet and I have to finish with a CESA, the worst case is that I don't have time for the recommended 3 minute Safety Stop.

 

[scubadada]

To put this into perspective for folks who are unfamiliar with redundant gas and/or RMV calculations, here is a list of various size cylinders and the equivalent pressure in an AL80. Many should be able to relate to this

19 cf 736 psi
13 cf 504 psi
6 cf 233 psi
3 cf 116 psi
1.7 cf 66 psi

 

[Bob DBF]

I never understand why so many folks hate on the Spare Air. As you said, it does what it says it does. Once you accept it is not a pony bottle, and is not a direct replacement for a pony bottle, you can focus on what it does do.

The Spare Air is a pony bottle, although a small one. I had one but sold it because it could not deal with the harsh conditions I used it in, although to be fair, my alternate took a beating but was easier to clean and repair than the Spare Air. I went back to diving without redundant air until recently, as I realized I was not as young as I once was. It still depends on the dive whether I actually carry the pony.

Hate usually comes from someone who was burned believing a sales pitch, or believes others are too stupid to see past the sales pitch and make up their own mind whether it meets their needs. That goes for most products, as well as the Spare Air. Other than that, its determining ones risk tolerance and just crunching numbers. The 19 that I chose to meet my needs is overkill or less than adequate, depending on who you ask.


Bob