Unable to breathe with nitrox enriched air

[beautybelow]

Sometimes people don't have to come right out and say that the "training sucked", but when I read some posts that's the impression I get from some instructors.

That and if I had taught them nothing bad would ever happen.

I have personally turned off, to fill, thousands of tanks and some that were turned on all the way with a little force were hard to turn off. New, serviced valves included. I could imagine a small handed person trying to turn the valve with the tank on their back would create some strain to say the least.

Turning it all the way on and backing off a notch is not such a bad thing in my opinion.

 

[Wookie]

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.

And as a sailor working in one of those steam plants that AfterDark built, I was taught to back off the valve 1/4 turn because a steam plant globe valve has a "back seat", in case there is a packing leak, the valve may be opened fully and stop the leak. If a steam plant valve is opened fully in the course of normal operations, the steam behind the back-seat may condense and cause a vacuum, which in turn will damage the packing, or cause a vacuum lock on the valve and not allow the valve to be easily closed.

Scuba valves are not designed with a back seat, there is tank pressure on the packing at all times if the valve is opened, therefore there is no reason ever to turn a scuba tank valve back 1/4 turn, or any other amount. I do it anyway, because it was what I was taught since I was 17, but it isn't necessary.

As an aside, there were a series of Sherwood scuba valves that would actually get stuck on their backseat for exactly that reason. If you opened the valve fully, high tank pressure would be behind the backseat and the valve would stick in the open position. The replacement seats were made to vent the back of the valve disc so they wouldn't get stuck open.

 

[DevonDiver]

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.

That's relevant - but still, safety should outweigh convenience.

Not having full access to your air is a safety issue. Not being able to turn off your cylinder after a dive is a convenience issue.

I've done nearly 5000 dives - and never had a stuck cylinder.

I've accompanied maybe 8000 divers during that time, each doing approx 3 dives with me (rough guesses) - that's another 24000 dives sample. Again, no cylinder valve sticking.

Is this really a problem with scuba tanks? Or is it just aimlessly regurgitated nonsense?

On the other hand, I and many divers have experienced insufficiently opened valves - which subsequently led to an OOA situation of vary degrees of severity (often occurring at depth).

Is that a problem with using 'good industrial practice' where it isn't intended?

 

[MXGratefulDiver]

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.

Agreed ... on both points. But human error often has less to do with training than it does with experience. I'll bet dollars to donuts that this person's training covered what to do in the event of an out of air emergency ... because they all do. So why did the OP decide to surface rather than following that training? I think that's probably the most important question to raise here.

The fact is, particularly among inexperienced divers, that it's much easier to remember your training while sitting in class ... or in front of your keyboard ... than it is when faced with a situation where all of a sudden you can't breathe. The reality of this situation is far different than the discussion and planned exercises you did in your OW class. And the urge to bolt is strong. Everyone was trained what to do in these circumstances. So why do you suppose we read so often in these accident reports that the diver bolted, when they were all trained to signal their buddy and share air?

Yes, you're right ... this was human error ... on multiple levels. And that's how accidents happen. But the only training issue I see was the question about nitrox ... clearly the OP doesn't understand that there's no physical difference between breathing nitrox and breathing air ... and that should have been made clear in the nitrox class. But that's not what led to the accident in this case ... and this WAS an accident. It just, fortunately, didn't lead to a casualty.

And that's really my point ... let's focus on what matters here ... both the cause and further prevention of this type of accident. Because that could save a life ... and that's really why this forum exists in the first place ...

... Bob (Grateful Diver)

 

[D_B]

I had an experience during training with my buddies valve , he had turned it turned so hard off after checking his tank that it was throughly stuck, requiring the instructor to use two hands to open it (I/we couldn't figure what was going on because his SPG was dropping when we were buddy checking , but the valve "had" to be on because I could not turn it further open .. we both learned from that )

... I treat them gently , turned all the way, but just enough to be open, or closed

 

[AfterDark]

That's relevant - but still, safety should outweigh convenience.

Not having full access to your air is a safety issue. Not being able to turn off your cylinder after a dive is a convenience issue.

I've done nearly 5000 dives - and never had a stuck cylinder.

I've accompanied maybe 8000 divers during that time, each doing approx 3 dives with me (rough guesses) - that's another 24000 dives sample. Again, no cylinder valve sticking.

Is this really a problem with scuba tanks? Or is it just aimlessly regurgitated nonsense?

On the other hand, I and many divers have experienced insufficiently opened valves - which subsequently led to an OOA situation of vary degrees of severity (often occurring at depth).

Is that a problem with using 'good industrial practice' where it isn't intended?

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!

 

[Jax]

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.)

Due to overly restrictive security procedures, I cannot like posts from work . . .

LIKE!

This bears repeating, and was certainly taught in mechanics' school for years. Still?

 

[Jax]

Agreed ... on both points. But human error often has less to do with training than it does with experience. I'll bet dollars to donuts that this person's training covered what to do in the event of an out of air emergency ... because they all do. So why did the OP decide to surface rather than following that training? I think that's probably the most important question to raise here.

The fact is, particularly among inexperienced divers, that it's much easier to remember your training while sitting in class ... or in front of your keyboard ... than it is when faced with a situation where all of a sudden you can't breathe. The reality of this situation is far different than the discussion and planned exercises you did in your OW class. And the urge to bolt is strong. Everyone was trained what to do in these circumstances. So why do you suppose we read so often in these accident reports that the diver bolted, when they were all trained to signal their buddy and share air?

Yes, you're right ... this was human error ... on multiple levels. And that's how accidents happen. But the only training issue I see was the question about nitrox ... clearly the OP doesn't understand that there's no physical difference between breathing nitrox and breathing air ... and that should have been made clear in the nitrox class. But that's not what led to the accident in this case ... and this WAS an accident. It just, fortunately, didn't lead to a casualty.

And that's really my point ... let's focus on what matters here ... both the cause and further prevention of this type of accident. Because that could save a life ... and that's really why this forum exists in the first place ...

... Bob (Grateful Diver)

Bob, in line with your excellent analysis . . .

When a person (soldier, in my case) fails to follow training, s/he is immediately put through drill, drill, drill until the proper reaction is second nature.

As you mention here, the OP was probably trained in the correct action, but resorted to instinctive bolt . . .

How much of that is due to a lack of instructor urging to drill? For some of us, practice is as natural as breathing. For others, once they check the block, they have no thought or desire to . .. for example, ever take their mask off underwater ever again.

Do instructors press practice drills enough?

 

[MXGratefulDiver]

That's a very good question, Jax ... and bears further discussion. But perhaps not here. I started a thread in Basic called "Do you always follow your training?" that is a better place to explore the answer ...

... Bob (Grateful Diver)

 

[The Chairman]

the OP was probably trained in the correct action, but resorted to instinctive bolt . . .

Training is best done in similar circumstances. Unfortunately, it's impossible to replicate the shear pucker factor that an unplanned OOA gives you. You can bet that I turn my student's air off while they are training in the pool. A few agencies have banned this practice so it's not the instructor's fault if they can't drill that into a student. BTW, they are inflated, at the surface and know when I am doing this. When the air sucks dry, they have to look around for a buddy, and if they can't see one, they kick like hell for as far as they can blowing bubbles the whole way. It usually only takes once for them to get the idea that they need to check their air before they descend and to keep checking it through the dive. I find that militaristic training, while having the appearance of being thorough, only serves to bolster the instructor's and sometimes the student's ego rather than to actually enable them to resolve a real emergency.