Unable to breathe with nitrox enriched air

[Ayisha]

Of greater concern to me are the rare incidents of debris coming loose inside the tank and lodging in / blocking the valve - a turn of the valve would not solve that and you would have no way to test for it in advance.

That's happened to someone I know and I've read about it elsewhere here. It usually presents in a head-down position. When the diver goes to an upright position, the valve usually unblocks and they get air again. Who knows what crud we're breathing even if it isn't enough to actually block the airflow.

 

[ktkt]

Note: he does say he has a SPG too .. that should have caught an almost closed valve during a breathing check ... he does not say if he did one though, only what his pressure was

Unfortunately, many people don't realize that you should watch your SPG as you are breathing your regs pre-dive and make sure the pressure is not swinging around (precisely to catch this tank barely cracked open issue).

 

[cruiser]

Saw this happen to my home bud's GF going down the Belize Hole, not a dive for any mistakes.

Then after we adopted the all-the-way approach (if you like tips, do it my way please, for those deckhands who like to fiddle with valves), we were lined up on a big boat and I noticed he turned mine all the way off. I was loud about it. " You turn screw divers every day. How can you get lefty-loosy righty-tighgty confused...?!"

LEFTY-LOOSY RIGHTY-TIGHTY RULES !!!

Why have we so adulterated this basic concept into something counter-intuitive and confusing that results in diver's air being accidentally turned off? In a sport where we have lots of steps to gear up, wouldn't it be easier to keep it simple when possible?

LEFTY-LOOSY RIGHTY-TIGHTY RULES !!!

 

[kdsmithjr]

It seems unlikely this is a nitrox issue.

Did you try your octo when u couldn't breathe through the primary regulator? I'm assuming you tested em all before and after u got in the water..

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It sounds as if the tank valve was only partially open. I see you are a low time diver, so here is a tip...Never "test" your regs by just breathing through them. At 3,000 psi, even if the tank valve is open just a crack, it will seen just fine. But as you descend, the partial opening will make it harder and harder to breathe. Also never, ever, test your reg by pressing the purge button and listening for air. again, at 3000 psi, if the value is open a crack, it will seen fine.
The way around all of this is to test your reg and octo by both breating from them while also looking at your pressure gauge. If you see your pressure gauge fluctuate with every breath, it means your tank valve is not fully open. Open your tank value fully by turning it all the way until it stops, then turning it back about 1/4-1/2 turn.
.

 

[kdsmithjr]

Well something is blocking the gas from moving. Possibilities are a blocked dip tube in the tank, or a dirty filter at your first stage inlet or a partially open tank valve. Take a look at the inlet filter on your first stage and make sure it looks clean. Moving the reg to a different tank can check if it is a tank valve issue. Also do make it a habit of reaching back and touching your valve at the start of dives. You really should be able to turn your valve on by yourself and have enough muscle memory to do so without thinking it through. If you can't now you may have to move your tank up a bit. What did you do the check the functionality of your reg and tank?

Could be, but this sounds so classically like a partially open valve to me. The easy and definitive test is to breathe thru the reg. If the pressure gauge drops with every breath (it should not move at all), it's probably a partially open taxk valve. I only have little over a hundred dives in nine months of experience but all my instructors taught me never to "test" my reg with the purge button and never to test by just breathing thru the reg and octo. I was taught to breathe from both while looking at my pressure gauge to make sure the needle does not move. if it does, check my tank valve.

 

[DandyDon]

LEFTY-LOOSY RIGHTY-TIGHTY RULES !!!

Unless you're dealing with left-handed threads. I've ran across some over the years, altho they are rare.

And I've got it backwards by viewing incorrectly at times. :silly:

 

[racerx_]

I think the vast consensus has been the possibility of a partially opened valve. I'm not sure why everyone who feels the same way needs to keep posting what's already been stated so many times

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[ianr33]

As I post about once every week....................

Either have valves off. Or full on. None of this 1/4 turn back stuff.

Either it breathes, or it does not.

Simple.

 

[Jax]

Okay -- so the

Fact - the OP couldn't breathe his regulator at ~2ATM.

Fact - OP did a CESA.

No other information is available.

Most probable cause valve not open as well as others

Causative factors - crew person rolled it closed and 1/4 turn open

Proper response - confirm hard breathing while looking at gauge with one hand, using other to check valve knob.

and / or - signal out of air to buddy and go on buddy's octopus while troubleshooting.

What happened - OP did not recognize this common issue.
- the OP did not try to troubleshoot but shot for surface
- the OP did not signal a buddy
- did the OP have a buddy?

All of the above, especially the buddy, is taught in OW training.

Ergo, either the OP received poor training, or . . .

 

[MXGratefulDiver]

Unless you're dealing with left-handed threads. I've ran across some over the years, altho they are rare.

Actually they're a lot less rare than they were a couple years ago, thanks to the growing popularity of sidemount. I have three left-handed tanks sitting in my garage at the moment ...

... Bob (Grateful Diver)