OOA after only a few minutes with a full tank at 17m

[Roy_W]

Hi All,

Had a little surprise this week.. We were three divers and I did my pre-dive check, on the surface, with buddy number one. Gas Ok - 220 Bars, Regulators Ok - Three deep breaths on Primary and Octopus, BCD Inflation Ok, the usual stuff.

We headed of into the water, reached our descent point and proceeded with our dive plan, heading of to our deepest point at 20m.

At the 17m mark I felt an unusual response from my regulator, I didn't understand what it was initially, it felt as though though something blocked the regulator after 1 second. After trying to take a second breath, same result. At this point I signaled to my buddy that I was OOA. Everything went calmly, he passed me his Octopus and we made a controlled ascent. There was no need to make a safety stop but at 8 m we slowed the ascent down, we had plenty of gas and everyone was together and the situation was calm..

Back on the surface, I inflated my Stab manually. And then I tried my Regulator again, everything was working fine....strange....both primary and secondary...

We returned to shore and verified everything, turned out that my bottle had not been fully opened. It had been opened enough to make gauges and regulators work on the surface but not enough that it could supply at depth...

I have no idea what happened that day, usually I fully open the valve and then do a half turn back.. Which is our standard procedure. Why it was only open at 10% or so I will never know.

Later I spoke to our instructors who mentioned that we should do a secondary test around the 3 - 5m mark, whereby you take a few breaths and carefully watch the SPG, if the needle wobbles even a little bit it could be sign of a non-fully open bottle..



Do any of you have any other techniques that could possibly help avoid this kind of situation.

( Went diving yesterday and to no-ones surprise I made a big point of controlling that the valve was fully open , we also did some tests whereby we progressively opened the valve and studied the SPGs reaction when breathing from the primary, it really doesn't take more that a quarter of a turn of the valve for the needle on the SPG to remain static and fool you into believing that all is OK, at least on the surface.)...

 

[Matthijs]

I once had a buddy who checked my valve by opening it up and turning it back a quarter turn. Turns out that instead of opening the valve, they closed it and opened it only a bit. At the surface this is indeed fine but it can screw you at depth. Since then I kind of dislike the whole turning it back a quarter turn. If you just fully open the valve, it will also fully close if you do it incorrectly. That way you'll at least figure it out right away.

 

[tursiops]

OP, when you did your three derp breaths at the surface, did you watch your pressure gauge? The needle should wobble if the valve is not fully open.

 

[mafi]

Don't do the half/quarter turn back. No reason with modern valves, it only adds to the confusion.

 

[Satrekker]

Sounds like you closed valve and did partial turn to open. As mentioned above, the turn back is totally unnecessary. Eliminate that completely. Also, I double check everything if anybody else puts a hand on my gear.

 

[diveUAE]

The same thing happened to me once - but instead of going to the surface after I got my buddy’s octopus he just opened my tank fully. Kind of scary to be ooa at 12m, but now at least I know I will not panic

After this incident we tried only opening the tank 1/4 turn and purge bot regulators - the needle on the spg did not move at all! So everyone who says to check with 2-3 deep breaths - you will not see anything. Period.

 

[Esprise Me]

I once caught a not-fully-open valve by watching the SPG while taking a couple deep breaths before splashing in. I know I opened it; the "helpful" boat captain who came up behind me must've closed it. But I don't know how far open it was; that's interesting that a quarter turn looked fine on the surface. I'll have to test that out. Meanwhile, I bought a tank with an indicator valve and check to make sure I can reach it while wearing it, in addition to the 3 deep breaths. Can't be too careful with your air.

 

[johndiver999]

A person who dives solo should probably have the knowledge, experience and skill to immediately open the valve when this type of problem arises without any aid or too much drama. Thanks for the reminder about opening valves.

Perhaps the most interesting comment made by the op is that , they experimented and found a quarter turn open was enough to prevent the spg needle from moving, but would be a problem at depth. This means that the very commonly recommended practice of checking be fore descent may be ineffective, however it WILL let you know if the valve is actually off.

 

[Roy_W]

The same thing happened to me once - but instead of going to the surface after I got my buddy’s octopus he just opened my tank fully. Kind of scary to be ooa at 12m, but now at least I know I will not panic

After this incident we tried only opening the tank 1/4 turn and purge bot regulators - the needle on the spg did not move at all! So everyone who says to check with 2-3 deep breaths - you will not see anything. Period.

This is exactly the reason that my instructors told me to retest at 3m-5m.. Apparently the needle will/should move when the pressure changes.. Strangely enough it's the first time that I have ever heard anyone talking about doing this check ( at least in my club).

 

[Steve_C]

OP, when you did your three derp breaths at the surface, did you watch your pressure gauge? The needle should wobble if the valve is not fully open.

Do this every dive. Caught a too helpful crewman on a dive in mexico.