Spare Air on deep but no deco dives??

[stevensamler]

I’m curious to get peoples’ views on this. I’ve never bought or used a Spare Air or similar extra bottle, what do people think about them? I’ve seen mixed reactions, including that if you’re really out of air at depth (say 110 or deeper) they don’t provide enough air to get to the surface without doing a CESA in any event. I’ve never (yet) had an issue or been in a dive where someone had an issue, and I carefully monitor my gas both with an air integrated Suunto and of course an analog SPG, and I stay near (ok, pretty near) to my buddy. But I guess you never know. So let me know what you think. Again, I stress that this is strictly limited to no deco diving. Oh, and there is almost always either a tank or regulator with air hanging from the boat at 15 feet.

Spare Air is a joke period , do Fundies.

 

[wetb4igetinthewater]

I tried to sell my slogan for SpareAir, but I was rejected

“SpareAir: helping divers drown at shallower depths since 1979”

And to think I hoped they’d love it

 

[Coztick]

As we ascend, the gas in our lungs expands. I think that's universally understood. So if a diver is ascending from depth he or she doesn't need to be huffing and puffing on their regulator, they can take slow breaths and just allow the expanding gas to vent from their lungs which gives them a lot more mileage out of what gas remains in their tank.




Lets assume the SAC rate of 1 is perfectly normal for every single diver in an out of air situation. It's a bit extreme but my point is that according to the linked article if a diver ascends at 60 feet per minute and does not do a safety stop the Spare Air will be sufficient even at a SAC rate of 1.0

While I totally agree with elevated consumption during a switch to an alternative regulator during an emergency, I'm certain that most divers would be much calmer after a switch to an adequate gas source.
Many claim CESA's from 100ft.
I am one to take the extra gas so that's never needed.

 

[MaxBottomtime]

“SpareAir: helping divers run out of air twice during the same dive since 1979”

Fixed

 

[wetb4igetinthewater]

I actually did a spreadsheet on the required ascent rates for SpareAir at different consumption rates from depths from 30 to 130 feet. You have to ascend like a Polaris missile of your gas consumption rate is too high or you are too deep

 

[KeithG]

Learn to dive in a buddy team.

Manage your gas.

Skip out on unnecessary gear.

Agreed. Since this is the advanced forum the proper answer is get a real pony bottle. If it was the basic forum the answer would be learn to properly buddy dive.

My buddy carries an AL80 and since she is not an air hog it becomes my spare AL40. This actually works both ways since I am not an air hog either.

 

[PfcAJ]

Agreed. Since this is the advanced forum the proper answer is get a real pony bottle. If it was the basic forum the answer would be learn to properly buddy dive.

My buddy carries an AL80 and since she is not an air hog it becomes my spare AL40. This actually works both ways since I am not an air hog either.

The advanced and basic answer is to learn to buddy dive.

Taking extra gear because you have a skill deficiency isn’t advanced.

 

[KeithG]

The advanced and basic answer is to learn to buddy dive.

Taking extra gear because you have a skill deficiency isn’t advanced.

Good point. I was thinking of solo divers who should have a pony as being advanced. I could have been clearer.

 

[KenGordon]

I’ve never (yet) had an issue or been in a dive where someone had an issue, and I carefully monitor my gas both with an air integrated Suunto and of course an analog SPG, and I stay near (ok, pretty near) to my buddy. But I guess you never know

The question comes down to whether your buddy is a reliable source of gas in the event you have a problem. Only you are in a position to work that out. First is your buddy reliable, and second are you disciplined enough to stay close?

Your buddy is your best plan. Gas planning is based arround the buddy carrying enough for both divers for an ascent - assuming you are properly planning gas.

If your buddy is not reliable or you are not close enough then you are solo diving and need to take appropriate redundancy, especially gas.

For a 30m dive you will have at least 3 minutes of ascent at an average 2.5 bar. With a moderate 20l/minute that is 50l/min or 150l. In fact though you will take longer, want a safety stop and breath faster. So really you want at least a 3l pony.

Personally I prefer a reliable buddy.

 

[mi000ke]

You can estimate how much air you will need to ascend from whatever depth you are planning for and see what is required for your SAC rate (mine is .4 cf/min under normal diving conditions). I computed my bailout air requirement from 100', which is generally my deep point, and came up with about 13 cf., using the following

1 minute at 100' depth to get sorted out (1 x 4 atm x SAC)
3 minutes to get to 15 feet at 30' per second ascent rate - average depth 58' (3 x 2.75 atm x SAC)
3 minute safety stop at 15' (3 x 1.5atm x SAC)
.5 min to surface (.5 x 1.25 x SAC)

Then doubled it to account for higher SAC under stress.

I suppose that under the minimal air requirement assumptions of heading straight to the surface from 100' with no safety stop, ascending at 60' feet per minute, and assuming no time to get sorted out at depth or that my SAC will be elevated, I would need about 2 minutes to ascend at an average atm of 2.5, which at my SAC rate of .4 would get me to the surface with a Spare Air. But I'd rather have a nice margin of safety and sling a 13 cf pony.