Snorkling with emergency air tank

I don't think there is a problem with using a "spare air" like device, at snorkeling depths, as long as you do not go inside anything.

30 feet sounds safe, worries about decompression at that depth are pretty small, given the amount of air that could possibly be in that little thing and thus the time spent at depth being short. When it runs out you'd have enough air left in your lungs to surface. You should still come up slow, though.

Recreational scuba depth around here is somewhere between 100 and 130 feet. I learned 100.

Quote: rxwine

Is there any value in your rebreathing some of your already breathed air? I was just thinking, if you exhaled some of your air into a gravity neutral underwater bag, you could potentially get some use out of it until you got to the surface. Seems better than breathing water.

I did this a lot when I was a kid, still would if needed. Though I use latex balloons, like for a kid's b-day. There is plenty of O2 in your exhalation, at least enough to give you a couple minutes.

YMMV

Quote: Face

I did this a lot when I was a kid, still would if needed. Though I use latex balloons, like for a kid's b-day. There is plenty of O2 in your exhalation, at least enough to give you a couple minutes.

Yes there is. That's why mouth-to-mouth breathing works in CPR.

But your exhaled air contains about 4% CO2, compared to about 0.04% in ambient air. When doing CPR, this doesn't matter, as each exhalation is fresh, and CO2 is non-breathable. But inside a closed loop, like a balloon, it builds up.

BTW, I was under the impression that 10 meters isn't deep enough to cause the bends. Wouldn't you need way more pressure than 2 atmospheres to dissolve nitrogen into the bloodstream?

The deepest I've ver gone is about 2.5 meters. It was in a hotel swimming pool. In the ocean I guesstimate about two meters. That was in Eilat, Israel, without any gear but goggles. I stayed down way under 30 seconds each time, and took some terrible underwater pictures.

I thought we already have nitrogen dissolved in our blood but that the sudden release of pressure is what would allow it to be evolved as nitrogen bubbles. The greater the depth the more time needed for ascent but I doubt 30 feet would make much of a difference.

Anyone have facts on this?

I certaily agree that caves or tunnels are not the place for amateurs to be lured. Spend too much time admiring the beauty and the device might be empty while inside the cave and that is when panic sets in.

You can get the bends from 10m/33ft depths.

For a single dive, you would have to be down for a very long time.

The stories I heard/read about it happening were from a bunch of shorter dives more or less consecutively, leading to a lot of time underwater and little time out of the water.

I did a Google search, this article from 1998 is either the one I remember or it is just more examples.

http://www.undercurrent.org/UCnow/dive_magazine/1998/ShallowWaterBends199810.html

Quote: Dalex64

For a single dive, you would have to be down for a very long time.
The stories I heard/read about it happening were from a bunch of shorter dives more or less consecutively, leading to a lot of time underwater and little time out of the water.

Given the cost of the devices this might be unlikely but a foolish vacation extravagence could be fatal.

I think this is a great idea. I'm surprised it took so long. I would definitely consider buying one of them and even investing in the company.

Quote: Nareed

BTW, I was under the impression that 10 meters isn't deep enough to cause the bends. Wouldn't you need way more pressure than 2 atmospheres to dissolve nitrogen into the bloodstream?

It just takes a lot of time at only 10 meters. Dive tables restrict you to 3.5 hours for your first dive. There is at least one case where a very long single dive to 10 feet produced symptoms of the bends, with the bottom time unknown. Presumably the guy was down there all day, probably with a feed to a compressor. The original cases of the bends in the 1840's involved workers who were under pressure for 7 hours at a time.

I said it was very unlikely that you could get the bends with these devices as you would have to have your friends pass you one after another until you had at least two dozen.

However, you could easily imagine somebody being ignorant enough to fill one of these tubes with pure oxygen so that he could do photography work. Unlike compressed air, pure oxygen could easily kill you at only 10 meters. I have done SCUBA dives with only partial oxygen mixes and you have to sign paperwork with every dive to protect the dive company if you have an accident.

The greatest danger is a lung rupture if you bolt to the surface because something spooked you (like a shark). That could happen with SCUBA gear, but at least you have training so you know to open your mouth.

Quote: Wizard

I think this is a great idea. I'm surprised it took so long. I would definitely consider buying one of them and even investing in the company.

note: Pretty bikini clad women not included.

Quote: Pacomartin

I said it was very unlikely that you could get the bends with these devices as you would have to have your friends pass you one after another until you had at least two dozen.

I was thinking more of a rich neophyte who simply surfaced briefly, obtained a new bottle and went back down. Does seem unlikely to be more than a four hour activity for even an enthusiast.

Pure oxygen is always fatal as its the carbonic acid from the CO2 that induces breathing.