Is it worth practising OOA?
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windapp
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What happens whe you run low air will vary vastly depending on your setup.
If you have a balanced first, and unbalanced second, you won't start breathing hard until close to the IP. At this point, you have serveral breaths left in a tank.
If you have both balanced, you may not start breathing hard until you have a few breaths left.
Unbalanced first, you will start breathing hard at around 500 psi, and it will get progressively harder.
The whole turning off the valve thing doesn't even come close to simulating a true low on air/ close to out of air situation.
I have run almost out of air due to an SPG/task loading issue, and I was grateful that I was in the first situation.
The warning sign is that your SPG reads less than 500 PSI.
One last thing. Don't every take your regulator out of your mouth until you have another source of air when you are OOA. In spite of what has been said here, you will probably have one last breath in your tank if you CESA as you rise and the pressure drops. You won't be able to take that breath if your regulator is flooded.
If you have a balanced first, and unbalanced second, you won't start breathing hard until close to the IP. At this point, you have serveral breaths left in a tank.
If you have both balanced, you may not start breathing hard until you have a few breaths left.
Unbalanced first, you will start breathing hard at around 500 psi, and it will get progressively harder.
The whole turning off the valve thing doesn't even come close to simulating a true low on air/ close to out of air situation.
I have run almost out of air due to an SPG/task loading issue, and I was grateful that I was in the first situation.
The warning sign is that your SPG reads less than 500 PSI.
One last thing. Don't every take your regulator out of your mouth until you have another source of air when you are OOA. In spite of what has been said here, you will probably have one last breath in your tank if you CESA as you rise and the pressure drops. You won't be able to take that breath if your regulator is flooded.
Naucrates ductor
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There's a pretty significant difference in the feel of running out of air depending on your reg and your depth. From one extreme to the other, with an old Conshelf in shallow water, you'll be able to tell you're getting to the bottom of the tank several minutes - maybe 20 breaths - before you're actually unable to get any more out of the tank. On the other hand, a high performance reg at 130' will only give you the subtlest of warnings before your last three or four breaths. If you really want to experience the deep thing, carry your test tank & reg in addition to your regular rig, & keep your primary reg in your hand while you breathe the test tank dry. (no, it won't hurt the tank 
) (you *can* get water in the test tank if you take it deeper after it's dry, but if you just come on up with it after the test, no sweat.) Once you get shallow, try breathing off the "dry" tank again... it may surprise you how much air's now available from the previously "empty" tank.
Again, all your experimenting needs to be with a rig that is completely separate from your "real" rig, where all your normal gas management precautions apply.
ND
) (you *can* get water in the test tank if you take it deeper after it's dry, but if you just come on up with it after the test, no sweat.) Once you get shallow, try breathing off the "dry" tank again... it may surprise you how much air's now available from the previously "empty" tank.Again, all your experimenting needs to be with a rig that is completely separate from your "real" rig, where all your normal gas management precautions apply.
ND
Reading these scenarios and practicing air sharing with your buddy makes me wonder...
How come the first stage does not do something to warn you. Like say have an audible alarm at less than 500 lbs or start to change the way the air flows at the same pressure. Something that would cause the air to draw in with a pulse so you would immediately notice it.
Keith
How come the first stage does not do something to warn you. Like say have an audible alarm at less than 500 lbs or start to change the way the air flows at the same pressure. Something that would cause the air to draw in with a pulse so you would immediately notice it.
Keith
Them
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windapp
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The scubapro MK7 did give an audible warning. It honked when your air was low.
You are, however, supposed to be monitoring your SPG. Except for a broken gauge that you didn't know was broken, there really isn't an excuse for going OOA. If you are task loading too much to monitor your SPG, give up the camera until you get better.
You are, however, supposed to be monitoring your SPG. Except for a broken gauge that you didn't know was broken, there really isn't an excuse for going OOA. If you are task loading too much to monitor your SPG, give up the camera until you get better.
Putting a warning device on a first stage is not that hard.. If you look at the diagrams of the different kinds of first stages, you will see that they are remarkably simple mechanical devices. If you are thinking of ways to adjust them to put in some kind of a warning, you realize that the easiest way to do it would be to attach a device that measures the flow before it is reduced by the mechanics of the first stage. You would probably do that by putting some kind of external port on that portion of the regulator and attaching a flow-measuring device to it. Since the first stage is behind the diver, you would need some way of making it apparent to the diver. The easiest way would be to put the measuring device on the end of a long hose so that the diver could check it regularly.
Good idea, but it's been done.
Good idea, but it's been done.
windapp
Contributor
I think you mean pressure measuring device.
By the way:
I saw a device on the highway that showed me how fast I was going, and thought "Wouldn't it be a great idea if they put one of those right in the car so you would always know?"
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I practice donating and receiving air on alternating dives, as long as our plan is not so tight as to preclude it.
I think you mean pressure measuring device.
By the way:
I saw a device on the highway that showed me how fast I was going, and thought "Wouldn't it be a great idea if they put one of those right in the car so you would always know?"
Some cars do have them. When the guy or gal driving that car stops you she usually gives you a piece of paper that shows how fast you were going and you have to sign it. Those courtesy notices though do get expensive.
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