An actual legitimate use for spare air???

[BRT]

I agree that my words are too strong but what you describe at the end of your post is not what I understood from his scenario.

What I understood is that you may run out of air at a deeper depth, then you ascend and elect to do a safety stop, because you have a spare air.

To me it’s iffy to say that this the recommended way to deal with an OOA situation at 100ft:

• run out of air at 100ft
• come back up to 15ft
• finish your spare air doing an optional safety stop

@AfterDark makes a good point that you’ll get more air as you get up.

Also to clarify, I am sure that you or @AfterDark can do this without any problem (hanging out and , it is not just what I’d recommend to everyone on the basic discussion forum if you run OOA.

You may not get more air coming up if you have a mechanical failure rather than just not careful to watch your pressure gauge.

 

[BlueTrin]

I carry a rubber hose in my truck. If I drive into a canal and find myself trapped in my truck under water, I insert the rubber hose and fart, should be enough air to get me to the surface.

Maybe you should attach a DSMB in the other end ?

 

[MaxBottomtime]

Would you feel the same if the diver had no spare air, got separated from a buddy and started an ascent from 100 feet with maybe 200 psi in their tank. What if they made a reasonable ascent and ended up at 15 feet with say 100 psi on the gauge.

There is no chance in Hell that I would ever be at 100 feet with only 200psi. None whatsoever. In more than three decades of scuba diving, I have never "ended up at 15 feet with 100psi" There have been times when I hung out in shallow water intentionally until my tank was that low, but I have never been surprised at how much air I had while underwater.

Getting separated from your buddy should be no factor in how much air you have. If you are at 100 feet with 200psi, chances are your buddy is somewhere nearby and also low on air. That's nothing but a Darwin Doubleheader waiting to happen.

 

[AfterDark]

They are 6 cu-ft now,

Spare Air – the original mini scuba tank for divers and more, available in 3.0 and 6.0 cu. ft. tank sizes

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.

 

[johndiver999]

There is no chance in Hell that I would ever be at 100 feet with only 200psi. None whatsoever. In more than three decades of scuba diving, I have never "ended up at 15 feet with 100psi" There have been times when I hung out in shallow water intentionally until my tank was that low, but I have never been surprised at how much air I had while underwater.

Getting separated from your buddy should be no factor in how much air you have. If you are at 100 feet with 200psi, chances are your buddy is somewhere nearby and also low on air. That's nothing but a Darwin Doubleheader waiting to happen.

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.

 

[tridacna]

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.

“Lots of situations”? Stuck SPG. Really? I’ve been diving since 1976 and it’s never happened to me or any of my buddies, students or other divers. What are you doing that makes it happen “lots of times”?

 

[Divin'Papaw]

I didn’t forget it but you did expose yours.

Diving with a 3 cf spare air is a false sense of security. Executing a planned solo dive well within gas reserves with a fully redundant 40 cf alternate air source along with the experience & training to use it and to deal with the most likely issues that may arise is not that.

 

[MaxBottomtime]

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.

I watch my gauges often enough to know if they were ever stuck, but I wouldn't be at 100 feet with 700psi, let alone 200.

 

[greeniguana]

I keep a few hazmat spare airs around the house. You never know.....

 

[seeker242]

An actual legitimate use for spare air???

Maybe getting some rope or debris off the prop of your 20' boat. That won't take more than 5-10 min.