An actual legitimate use for spare air???

[yle]

I have seen one indisputable legitimate use for Spare Air, and the tiny 1.7 cu ft version at that.

Diving at the aquarium, i.e. working in the tanks which have a max depth of around 30 feet, OSHA had some kind of requirement that all divers must have a redundant air supply. So the aquarium stuck the little SA on on the BCDs and presto! OSHA requirement was satisfied.

(Worth noting: we did regular safety training, including CESA from the bottom of the deepest tank. No one had a problem with this skill and we all generally agreed that, in the event of an air supply problem, using the SA would likely take more time and hassle than just a simple CESA.)

 

[RyanT]

If it’s good enough for cave divers it’s good enough for me

I'm validated! I was actually thinking about this for when I start my cave training, I was going to suggest this as a reasonable alternative to my instructor. I was thinking about something like a bandolier, where I could stash a whole string of them. I'd just discard each one as I depleted them one on the way out! But now that I've seen the video, clearly just one would be plenty for a long cave penetration! In fact, I'm not sure why I bother with heavy doubles at all.

 

[BRT]

Just right for dry suit inflation!

I have an awful SAC rate I'd get 3 breaths from one and six from the other. On the other hand I'm not prone to panic so 2 questions. Could I make it to the surface from 100FSW with a 3 or 6 cuft tank? Yes, would it be a happy ascent complete with SS? No, it would be a trip into the past with a 60 FPM ascent rate and no SS, the way we dove when I got certified.

So if you have a bad SAC rate or breath heavy/rapidly when presented with an emergency that maybe life threatening 3 or 6 cuft of air maybe be something you'd want to think hard about. I solo dive with small or larger IDs depending on the dive. My 19 cuft pony spends most its time strapped to a rack.

And you get 80 breaths out of an AL80?

 

[BRT]

You're missing a key point. It's called contingency planning. It is covered thoroughly in any Solo/Self-Reliant Diver course. When it comes to an alternate air source you carry enough gas to ensure that in the event of a gas emergency at the deepest planned depth you can (1) take 2-3 minutes at depth to sort things out and (2) safely & slowly ascend to the surface. Unless you are doing a 3' dive a 3 cf alternate air source is NEVER going to meet that criteria. For the majority of folks diving within recreational depths, an AL40 will meet that criteria. For many an AL30, AL19 or even AL13 will as well based upon their SAC and their planned depth.

You also want to factor in the effort of carrying the alternate air source. An AL40 or AL30 are frequently discussed because they fit nicely a compromise between ease of carrying it as a stage relative to the gas provided. An AL80 does give you more gas but it is also more work to carry it and the need for that much gas just isn't there.

It all comes down to planning.

I'm assuming you always carry at least an AL13?

 

[Divin'Papaw]

I'm assuming you always carry at least an AL13?

If solo and diving deeper than snorkeling depth I always carry an AL40 pony. Always.

If diving with an unknown buddy I also carry it. Always.

When shore diving here in South FL I’m only diving to 20’ or so with most of the dive being 10-15’. I don’t bother with the pony in that instance. If I had a major gas issue I’d just surface.

 

[BRT]

When you travel do you bring your 40 or rent one?

 

[AfterDark]

Wow I wish I had the same faith you have in the accuracy of my SPG's. There are lots of situations where the needle on a mechanical gauge got stuck and was reading a higher level than actual.

Wow what kind of SPGs do you use and why do you keep using them?!

The only mech SPG's issue I've had in 50 + years are spool issues, leaking. A 200 psi deviation is manageable and should never cause an alert diver to be low on air.

 

[AfterDark]

And you get 80 breaths out of an AL80?

Could be I don't use 80ALs however.

 

[Divin'Papaw]

When you travel do you bring your 40 or rent one?

I don't typically travel and dive. If I'm traveling and diving it's almost always driving. On the VERY rare occasions that I fly to dive (if I were solo) I would absolutely rent a pony. AL40 if possible otherwise an AL80 and I'd bring a stage kit with me. Easy enough. I've slung an AL80 plenty of times. But I've never done that. On the 2-3 occasions when I flew to dive I was always diving with a buddy. In that instance I did not sling a pony.

 

[Brett Hatch]

Skimming through this thread, I can't help but think of Betteridge's law of headlines, which states:
"Any headline that ends in a question mark can be answered by the word no."

Have we finally discovered an actual, legit use for Spare Air? No.