what reasons have you seen people not pass certifications?

[bracko]

When I teach the OOA exercise, I don't shut the student's air off completely, because it teaches nothing. Instead I shut it off and crack it slightly open, watching the gauge until I see it wavering near zero. The diver will feel that it is hard to breathe rather than simply go out of air.

good idea, noted and thanks.

although i have noticed that most (85%ish) of students refuse to let the needle pass about 50bar and furiously give the OOA signal as it passes that point. I'm not sure if when i did it to myself i was breathing much slower (and obviously in control of my own tank) but at 50bar i was still breathing fine and dandy.

 

[boulderjohn]

good idea, noted and thanks.

although i have noticed that most (85%ish) of students refuse to let the needle pass about 50bar and furiously give the OOA signal as it passes that point. I'm not sure if when i did it to myself i was breathing much slower (and obviously in control of my own tank) but at 50bar i was still breathing fine and dandy.

50 bar is no problem. You won't notice anything until you are down to the last few breaths.

Don't let the students see the needle. They should not react until they feel something.

 

[hypertech]

I remember doing this skill in the shallow end of the pool. We watched the air gauge to see how long it took to bleed off the pressure. Then, when the air choked off, the instructor turned the tank back on. No big deal and not a single student bolted (though we could have just stood up if they did).

Surely, your instructors so set on turning out above average students didn't put up with 85% of their students refusing to complete the skill?

 

[boulderjohn]

I remember doing this skill in the shallow end of the pool. We watched the air gauge to see how long it took to bleed off the pressure. Then, when the air choked off, the instructor turned the tank back on. No big deal and not a single student bolted (though we could have just stood up if they did).

Surely, your instructors so set on turning out above average students didn't put up with 85% of their students refusing to complete the skill?

It's supposed to be done twice. Once just to get the hang of it, and once leading the diver to seek an alternate from the buddy and complete a swim while breathing off the buddy's regulator. It is supposed to be done in the deep end of the pool. Even if the instructor shuts the student's air off completely, the instructor turns it on as soon as the student signals OOA. The student will then get air instantly, so the student is OOA approximately 0.5 seconds. If that is explained, I can't imagine any student having an issue with it. IMO, it really doesn't do a whole lot as an exercise, and it would not break my heart to see it go away.

 

[bracko]

I remember doing this skill in the shallow end of the pool. We watched the air gauge to see how long it took to bleed off the pressure. Then, when the air choked off, the instructor turned the tank back on. No big deal and not a single student bolted (though we could have just stood up if they did).

Surely, your instructors so set on turning out above average students didn't put up with 85% of their students refusing to complete the skill?

1. it's done at our shop in the deep end.
2. They make the OOA signal, i turn on the tank... no "yeah, i see the hand signal, but i reckon you're still okay to keep breathing" doesn't really create a high level of trust between DM & student.

I don't have my instructor manual on me at the moment, but I'm guessing the requirement is not "to have the student suck the regulator completely dry, surface than punch the DM"

John, yeah we're still perfecting the pool skills with my instructor whom i usually work with, but we're looking at doing it as a bit of a game... DM turns tank off, student swims a few metres down the line of students and picks the one (s)he wants alt air from, makes the signal then alt air ascend kind of like a duck, duck, goose game

 

[hypertech]

I just checked my instructor manual (PADI), and unless I'm missing it, this isn't even a required skill at all. It seems to be more of a very common extra credit activity. It has been a long day, so if I'm just missing it, someone please correct me.

I'll also note that there is nothing that requires you to be out of air to practice the out of air drills. Your duck duck goose game sounds like an unnecessary risk to me.

 

[boulderjohn]

I just checked my instructor manual (PADI), and unless I'm missing it, this isn't even a required skill at all. It seems to be more of a very common extra credit activity. It has been a long day, so if I'm just missing it, someone please correct me.

I'll also note that there is nothing that requires you to be out of air to practice the out of air drills. Your duck duck goose game sounds like an unnecessary risk to me.

From the 2010 manual pages 44-45 (and it hasn't changed since I was an instructor).:

Dive 2 Performance Requirements
At the surface:
1. Perform the buddy predive safety check.
2. Demonstrate appropriate deep-water entry.
3. Clear a snorkel using the blast method, then resume
breathing through it without lifting the face from the
water.
4. Exchange snorkel for regulator and regulator for snorkel
repeatedly without lifting the face from the water.
5. Swim at least 50 metres/yards while wearing scuba and
breathing through a snorkel.
6. Adjust for proper weighting — fl oat at eye level at the
surface with no or minimal air in the BCD and while
holding a normal breath.
7. Orally inflate a BCD to at least half full in water too
deep in which to stand, then fully deflate it.
8. Remove weights using the quick release mechanism
with minimal assistance
9. Remove weights, scuba unit and fi ns (if necessary) in
water too deep in which to stand and exit using the
most appropriate technique. (Buddy assistance allowed.)
Underwater:
10. Descend using the fi ve-point method.
11. Remove, replace and clear a mask.
12. Breathe without a mask for at least one minute.
13. Disconnect the low pressure hose from the infl ator in
shallow water (either underwater or at the surface.)
14. Respond to air depletion by signaling “out-of-air” in
water too deep in which to stand.
15. Ascend using the five-point method.

Dive 3 Performance Requirements
At the surface:
1. Perform a tired diver tow for 25 metres/yards in water
too deep in which to stand.
2. Demonstrate the cramp removal technique for self and
buddy (at the surface or underwater.)
Underwater:
3. Use both oral and low-pressure BCD infl ation to
become neutrally buoyant. Gently rise and fall in a
controlled manner, during inhalation and exhalation.
4. Swim at least 10 metres/yards while maintaining
neutral buoyancy.
5. Respond to air depletion by signaling “out of air,” and
securing and breathing from an alternate air source
supplied by a buddy. Continue for at least one minute
while swimming.

 

[bracko]

can't be bothered flogging a dead horse actually.

many ways to skin a cat, every shop, instructor, DM has their own thoughts on what students might classify as a fun extra.

 

[halocline]

I was curious as to how many people have seen people not pass their open water certification and why they did not pass them.

There were several OW student failures at the dive op where I did my DM internship. Occasionally students would get certified as scuba divers, not OW, sometimes no certification but an invitation to continue working on the skills in order to pass. The typical reasons were inability to do some of the skills, inability to follow the instructor's directions, or general inability to control themselves in the water to the point where panic would be a real concern if they were diving unsupervised.

I was actually a little impressed that the instructors 'held the line' on skills and passing ability; this was in a dive destination and sometimes resort areas get a bad reputation for just passing anyone. It is true that while most of the students I encountered there did pretty well, there were a few taking up diving on a whim because they were in a nice tropical destination and those often didn't do as well. Occasionally we'd get a couple where one of the partners was dying to dive and the other was scared of the water and just could not get through the skills. Not always the gender you might guess though!

 

[g1138]

The first stage of your regulator is designed to deliver air to you at roughly 140 PSI more than ambient pressure. The deeper you go, the more pressure it provides you.
Wrong, the deeper you go the harder it is to breathe. You always get 140 PSI intermediette pressure. With an Open piston this is a problem, once ambient water pressure reaches 141PSI, not more air from your 1st stage, it's shut tight. With a closed 1st stage this isn't an issue at all, you'll always get 140psi in the 1st stage, provided a greater pressure in the tank
When a tank starts getting near what we consider to be OOA status, it is no longer able to deliver air at the required pressure. There is still air in there, though. The diver has to suck harder on the regulator to get it out because there is not enough air to deliver it at 140 PSI above ambient pressure. The diver at depth will usually feel it becoming harder and harder to breathe for several breaths before no air is available. [I know the feeling well because I use multiple tanks for decompression dives, and I don't switch off my first one until I feel that first hard breath.)

If a diver does indeed go out of air and ascends, there is no expansion of air in the tank. The tank is an inflexible container, and the air inside has no idea that external pressure is changing. The first stage of the regulator knows, though, because external water pressure is used to assist the regulator in delivering air. (That's how it is able to increase the pressure as you go deeper.) Consequently, as you ascend, before long the water pressure around you will diminish to the point that there is now enough air in the tank for the regulator to give it to you above ambient pressure. If an OOA diver retains the regulator as taught in the CESA exercise, and if he or she were to exhale too much air on ascent, simply inhaling will give another breath--and then another and another.

P1/V1 = P2/V2
Pressure in the tank is P1 Outside pressure is P2
Volume and temperature stay constant.
You have a tank with 100 PSI in it which is below intermediate pressure (1st stage). Outside you're at 90' which equates to ~39.6PSI. (FSW is .445 psi/ft)
As you rise to 10ft you get ~44psi of pressure

P2 is decreasing in pressure. Which allows for a lower ratio between P1 and P2.
Therefore at depth when you're out of air and go up, your ratio between P1 and P2 decreases allowing for the pressure of your tank to escape more easily, or in your case, allowing you to breath easier.
At that point you may not be able to get pressurized air, but given most stages are downstream, you can actually suck air from the tank.

There's also air in your hoses which will expand.

So even at depth when you're completely out of air, ascending WILL give you an extra breath