Unable to breathe with nitrox enriched air

[gcarter]

Really? Sidemount uses left hand threads? Why?

 

[MXGratefulDiver]

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 . . .

or ... feces struck the fan, OP reacted before thinking ... OP surfaced (safely) and thought to himself "I'd better find out what happened so I can make sure it doesn't happen again" ... ergo, OP is here looking for answers.

Let's not discourage that attitude ... it's healthy.

Yanno ... it's real easy for experienced divers to forget what it was like to be new. Sure, you learned things in class. Sure, you probably even practiced them a time or two. The fact is that sometimes in the real world we don't do what we were trained to do. Believe it or not, I've even seen that in an experienced diver from time to time. Even more unbelievable, I've done it myself. We're all human, and and humans don't always do what they're supposed to.

The smart diver says to himself "wow ... I'll never do that again" and learns from it. All indications are the OP is trying to be a smart diver. Let's not toss him under the bus here. If you have something constructive to add, say it. If not, please move along.

Believe it or not, I bet there isn't a single person reading or replying to this thread who hasn't made a mistake, or reacted to a sudden, surprising circumstance in a manner that didn't strictly follow what they had been trained to do.

Let's save the "your training sucks" theme for a different thread ... please ... it ain't helping anything in this one ... and it sure as hell ain't providing any constructive answers to help this guy respond better the next time ...

... Bob (Grateful Diver)

 

[MXGratefulDiver]

Really? Sidemount uses left hand threads? Why?

Left tank has valve handle on the usual side ... right tank has valve handle on the opposite side.

Perhaps that's a subject better discussed in the side-mount forum ...

... Bob (Grateful Diver)

 

[DevonDiver]

Open your tank value fully by turning it all the way until it stops, then turning it back about 1/4-1/2 turn.

I know most/many instructors teach this - but I've yet to hear a valid explanation as to why it is necessary.

At best, I've heard some regurgitated, unquestioned, nonsense about "valves sticking". Ask them if they've ever had a valve stick shut when not 'turned back'... nope.. never happens.

On or Off. That way, you can't get confused and leave yourself with insufficient air supply at depth.

As others have mentioned - a proper buddy check eliminates the risk - but then, the majority of divers/customers I see don't perform anything even close to a proper buddy check.

OP surfaced (safely) and thought to himself "I'd better find out what happened so I can make sure it doesn't happen again" ... ergo, OP is here looking for answers.

Let's not discourage that attitude ... it's healthy.

Let's save the "your training sucks" theme for a different thread ... please ... it ain't helping anything in this one ... and it sure as hell ain't providing any constructive answers to help this guy respond better the next time ...

There is a problem with diplomacy in some of the responses. I think that the thread would have been better placed in 'Near Misses and Lessons Learnt' - which would have put a more positive context to the debate. i.e. learning lessons, rather than accident investigation.

That said, if the cause was insufficiently/partially opened valves then the primary contributing factor is Human Error. Again, if correct, then this was confounded by further Human Error, as the fault was not diagnosed during pre-dive safety checks. As such, the involved party's standard of training, or effective application of that training, are the most significant issues that need to be raised.

However, it's important to raise those points objectively. There's simply no scope for having a 'holier than thou' attitude. I suspect that most of us who immediately recognized the potential for human error with respect to the valves, do so from personal experience of making the same mistakes. I certainly did.

 

[gcarter]

I know most/many instructors teach this - but I've yet to hear a valid explanation as to why it is necessary.

At best, I've heard some regurgitated, unquestioned, nonsense about "valves sticking". Ask them if they've ever had a valve stick shut when not 'turned back'... nope.. never happens.

On or Off. That way, you can't get confused and leave yourself with insufficient air supply at depth.

As others have mentioned - a proper buddy check eliminates the risk - but then, the majority of divers/customers I see don't perform anything even close to a proper buddy check.

I would blame old plumbing. Leave a valve open for a long time, it is more likely to stick and be hard to close if it was opened to the stops.

I would think that a scuba tank would have to be pretty big to provide enough air to warrant leaving the valve open long enough for it to stick, though

 

[DandyDon]

As others have mentioned - a proper buddy check eliminates the risk - but then, the majority of divers/customers I see don't perform anything even close to a proper buddy check.

It was my buddy who turned it off once, but at least it was all-the-way and I knew before splashing.

That said, if the cause was insufficiently/partially opened valves then a primary cause is Human Error. Again, if correct, then this was confounded by further Human Error, as the fault was not diagnosed during pre-dive safety checks. As such, the involved party's standard of training, or effective application of that training, are the most significant issues that need to be raised.

The time I got down to 20 ft before noticing, it was a sneaky crewman who'd turned if off and back open 1/4 while I was crawling up for back roll. I thought he was just steadying me. After that, I explained my tipping would require all-the-way valves and no problem.

There is a problem with diplomacy in some of the responses. I think that the thread would have been better placed in 'Near Misses and Lessons Learnt' - which would have put a more positive context to the debate. i.e. learning lessons, rather than accident investigation.

At least no one ragged him for saying his air was enriched with nitrox. :laughing:

 

[Quero]

The problem is that some people, when you say, open the valve all the way, will crank it open, and then it can stick and require a lot of force to close. I tell my students explicitly NOT to crank it open hard but instead to turn the handwheel with two or three fingers until it stops turning. (FWIW, cranking it shut also makes it hard to reopen the tank, which tells us that it's not so much a question of the valve actually seizing up over time, but simply abusing the mechanism by applying too much force at either the open position or the closed position.)

 

[DevonDiver]

The time I got down to 20 ft before noticing, it was a sneaky crewman who'd turned if off and back open 1/4 while I was crawling up for back roll. I thought he was just steadying me. After that, I explained my tipping would require all-the-way valves and no problem.

That happened to me just last week. I was about 10 minutes into the dive before I noticed my SPG needle fluctuating as I breathed. Reached back, fully opened the valve and continued the dive with no problem.

I always go 'fully on' or 'fully off'... so it was easy to diagnose that my valve had been 'fiddled with' by someone else

Makes me want to add 6" of barbed wire to my dive kit... and wrap it around the tank handle once I've got myself set-up.

The problem is that some people, when you say, open the valve all the way, will crank it open, .....abusing the mechanism by applying too much force at either the open position or the closed position.)

That's true. So basically, many dive pro's are teaching an unnecessary and potentially dangerous procedure ("1/4 turn back") purely to prevent wear and tear to the cylinder valve.

Whereas, alternatively, they could simply take a little time to ensure that students understood that the cylinder valve was a relatively delicate mechanism, requiring no forceful manipulation, and should be treated with care.

 

[The Chairman]

Left tank has valve handle on the usual side ... right tank has valve handle on the opposite side.

Perhaps that's a subject better discussed in the side-mount forum ...

... Bob (Grateful Diver)

They usually operate lefty-loosey though... just on the opposite side of the tank. That being said, my left hand tank gets turned off every now and then. I hate it.

As for the "hard to breathe", I concur with most, that in the excitement the valve may have been left on. However, I have had two contaminated tanks in my diving career. The one with lots of CO was hard to breathe after a LONG time underwater. I was throwing up for a while before it got to that. BTW, never underestimate how disorienting/debilitating this kind of thing is. Way before that incident though, I had one that had become oil fouled from a compressor filter breaking up. Every breath was tough, right from the beginning. I didn't really smell anything until I got back to the surface, but it was a lot like the OP described. Yuck! I belched up oil contaminates for the rest of the day.

 

[AfterDark]

I know most/many instructors teach this - but I've yet to hear a valid explanation as to why it is necessary.

At best, I've heard some regurgitated, unquestioned, nonsense about "valves sticking". Ask them if they've ever had a valve stick shut when not 'turned back'... nope.. never happens.

On or Off. That way, you can't get confused and leave yourself with insufficient air supply at depth.

The reason for the 1/4 turn is so the knob will turn freely in the correct direction. This comes from mostly non-diving situations mainly industry were combustiable gas tanks were unabled to be turned off because they were 1. turned back too tightly for the next person to move 2. it was turned back sung but has been sitting so long it will not move. 3. A valve was off but was turned on because of panic. It does need to be backed off a 1/4 turn, just backed off a bit from full stop. In a situation where a diver may need to turn a valve off that diver will know before completing a full turn if the turn is in the right direction. Or a quick check will confirm the valve is open as it hits the stop as soon as it is turned in the correct direction.

I worked in a shipyard for 20 years and it was considered "good shop practice" to back a valve off a "CH" as I was told after it was turned to full open stop. I suspect this was carried over to diving early on and it is not wrong or right it is just a practice that is wide spread and, with no adverse affects that I know of.

The most important thing to take from this thread IMO is to be certian that NOBODY TOUCHES YOUR GEAR AFTER YOU CHECK IT. That is one of the things I ask of charter crews not to touch my gear. If ever a crew insisted on fingering my gear, they will get no tip from me and they will know why!