OP
johndiver999
Contributor
Good thing she didn't object to you filling her bed! LOL
SSI Emergency buoyant Ascent : Training Video
- Thread starter johndiver999
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SlugLife
Contributor
Exactly. Depending on hoses attached, you get 1-3 breaths from a pressurized regulator on the surface. With a tank running low, it'll be more gradual.
That's a clever way to simulate it. I have a completely empty tank, and a transfil-whip. I might transfil to about 150 and breathe it down (on the surface) just to see what it's like, perhaps count breaths, and see when I notice a drop.
Obviously at depth it's different for 2-reasons. (1) You're breathing it down faster, depending on depth and (2) your regulators are fighting ambient pressure.
Which reminds me: 1 ATM = 14.7psi. So if I'm doing my math correct, at 90ft, a 60psi tank would be "empty." However, if you start surfacing, you may be able to squeeze more breaths out of an "empty" tank, which is not something I've ever heard anyone else say. (I didn't just say something stupid I hope?)
OP
johndiver999
Contributor
yes you should have been taught that as you ascend with a very low tank, the decreasing ambient pressure will allow the tank to deliver more air on ascent. this is one very important reason why we are told to keep the regulator in mouth on an emergency ascent (an MT tank might and probably will deliver more air). A lot of people will say the air in the tank expands on ascent, which is technically wrong, but in practice, it is basically what it feels like.
If you are going to experiment with breathing down a tank, you might benefit from this.. If you are diving and suspect that your tank is very low, just take a super hard and fast breath from it. If it is "low" you will feel a constriction toward the end of your inhalation. Regardless of what the spg says, this means you are very low on air, A mechanical spg is not going to be very accurate or useful at really low pressures, so this is probably more useful than looking at the gauge. In other words, regardless of whether your spg says 50 or 200 psi, it really doesn't matter, the reality is, you are VERY low on air. I can get quite a few inhalations from my current rig, even when the spg looks to be pinned to zero.
If you suck really hard at depth, you will have some warning of a really low tank. Conversely, if you are doing macro photography and not moving a muscle, trying to breathe really slow and gently, then you can suck a tank down very low without feeling the constriction. Then when you get scared and try to take a big hit, it feels like you are getting (almost) no air. And if you then press the inflator at the same time you try the next inhalation, it will be REALLY slow since two devices are drawing down the intermediate pressure in the reg.
SlugLife
Contributor
If I had a Scuba YouTube channel, it might make interesting and informative content. Maybe I should create a page of notes somewhere for ideas if I ever do start such a channel, hah!
It might also be cool to compare the difference between what the same exercise is like on land, versus 30ft, 60ft, or 90ft. Start with 200psi on the surface each time. Since I dive sidemount, have a bunch of tanks and regulators, it would be EASY to do safely. I might be able to even test if the regulators flood or not. "Turns out I can get another ?? breaths by going up from 90 to 60ft." Since it's winter and I don't have a dry-suit, I'm probably just going to try the on-land version for now.
Good point. I have AI & an IP gauge (which I drilled holes in the back), which might actually help with monitoring what's happening.
It might also be cool to compare the difference between what the same exercise is like on land, versus 30ft, 60ft, or 90ft. Start with 200psi on the surface each time. Since I dive sidemount, have a bunch of tanks and regulators, it would be EASY to do safely. I might be able to even test if the regulators flood or not. "Turns out I can get another ?? breaths by going up from 90 to 60ft." Since it's winter and I don't have a dry-suit, I'm probably just going to try the on-land version for now.
I try to keep a slow-steady pace throughout most of my diving. I also always dive with redundant air and have never been surprised by the amount of air remaining, so the scenario for me is more of a curiosity than a safety issue.
Using a crappy, not tuned regulator will give you a couple of minutes of warning, a unbalanced piston first stage even more.
When I'm working in shallow water I don't use a pressure gauge because the pneumatics destroy them quickly and the extra hose gets stuck in the concrete forms or armature. My apeks that has not been service in 4 years starts breathing hard at 10-15 bars giving me plenty of time to get back.
My fancy aqualung goes from easy breaths to no air in 2-3 breaths, damn those precision tuned pieces of engineering.
When I'm working in shallow water I don't use a pressure gauge because the pneumatics destroy them quickly and the extra hose gets stuck in the concrete forms or armature. My apeks that has not been service in 4 years starts breathing hard at 10-15 bars giving me plenty of time to get back.
My fancy aqualung goes from easy breaths to no air in 2-3 breaths, damn those precision tuned pieces of engineering.
I have done such comparisons.
When I was first doing tech diving, we would deal with the fact that our primary diving site was removed from good gas supply by wearing double tanks but breathing off of a single--essentially the same as starting the dive breathing off a pony. When we finished off the stage, we would switch to the doubles. When we were done with the dive, we still had enough in the doubles for the next dive, which we would again begin by breathing off a single tank. I therefore got a lot of practice breathing single tanks down at different depths, and I assure you, you get plenty of warning.
When I am finished diving at that remote location early on a Sunday afternoon, I face a 6+ hour drive, including mountain passes. It takes about an hour to pack, and I put an oxygen bottle in the front seat with me. I breathe from it for about the first hour of the trip home, and I sometimes finish it off about that time. Again, I get a number of breaths after it first starts getting harder to breathe.
Yikes!
Don't know if I care for that exercise; have never had to jettison weights or ever had my air intentionally turned off, in decades of diving, particularly during some BS training (or there'd be trouble) -- and some of those absurd hand signals called to mind that fraudulent though, admittedly hilarious “ASL” interpreter at Mandela's 2013 funeral service, whose gestures bordered on some classic Motown moves . . .
And, just for some good measure:
Don't know if I care for that exercise; have never had to jettison weights or ever had my air intentionally turned off, in decades of diving, particularly during some BS training (or there'd be trouble) -- and some of those absurd hand signals called to mind that fraudulent though, admittedly hilarious “ASL” interpreter at Mandela's 2013 funeral service, whose gestures bordered on some classic Motown moves . . .
And, just for some good measure:
Years ago, the Director of Instruction in the shop where I worked wanted me to teach the skills to the new divemaster candidates, and he wanted me to use precisely the same methods he had learned in his IDC in Roatan a year or two before. (Yes, out Director instruction was actually a fairly new instructor; I had helped in his DM certification only a year before that.) He wanted to be able to have the students look at those videos and do precisely the same thing.
Those videos were just like this one--totally overdone with far too many steps and far too many signals. They were also done on the knees. Put them together, and there was no way I was going to do it. He said they had to be done that way so we could be sure in the future that students get good scores if they go on to the instructor exam. He especially was afraid they could get scored lower if they did the skills neutrally buoyant.
I don't remember exactly what I asked when I wrote to PADI about it, but I got an immediate phone call from someone in the training department, the very man who had done my IE years before. What he said was illuminating. He said that the big IDC companies, like the one in Roatan, want to be sure every student gets a great score on the IE. So they create an instructional process for each skill that includes every single step and every single signal that any random examiner might like to see. Then they drill their students over and over and over until everyone is doing the skills exactly the same way. He said that if you were to line them up and have them start a skill demonstration at the same time, it would look like a synchronized swimming routine. He agreed that it is all overdone. He was my examiner, and he gave me a top score on every skill I demonstrated, and I didn't do anything remotely like that.
And by the way, he said they preferred it when students performed the skills neutrally buoyant.
Today that same Roatan shop has a new set of videos--all skills done neutrally buoyant.
Those videos were just like this one--totally overdone with far too many steps and far too many signals. They were also done on the knees. Put them together, and there was no way I was going to do it. He said they had to be done that way so we could be sure in the future that students get good scores if they go on to the instructor exam. He especially was afraid they could get scored lower if they did the skills neutrally buoyant.
I don't remember exactly what I asked when I wrote to PADI about it, but I got an immediate phone call from someone in the training department, the very man who had done my IE years before. What he said was illuminating. He said that the big IDC companies, like the one in Roatan, want to be sure every student gets a great score on the IE. So they create an instructional process for each skill that includes every single step and every single signal that any random examiner might like to see. Then they drill their students over and over and over until everyone is doing the skills exactly the same way. He said that if you were to line them up and have them start a skill demonstration at the same time, it would look like a synchronized swimming routine. He agreed that it is all overdone. He was my examiner, and he gave me a top score on every skill I demonstrated, and I didn't do anything remotely like that.
And by the way, he said they preferred it when students performed the skills neutrally buoyant.
Today that same Roatan shop has a new set of videos--all skills done neutrally buoyant.
Nobody seems understand the bobbing. What is happening is an oral inflation at the suface...bobbing up to grab some air, comfortably sinking slightly to blow it into the oral inflator. To you, it looks like needless and mysterious bobbing; to me it looks like a good exercise and a well-trained student.
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