Out of air emergency at 105 feet

[Thalassamania]

It seems to me that the DM was not qualified for the job.

As far as bye-bye is concerned ... I'd not have considered it unless the DM has given me an OK, handed my primary back and waived at me. Then I'd have let him go and rejoined the group.

 

[nuts4corals]

Oh and the question posted in regard to the DM passing by other people... I think he must have passed by others to get to me. Not really sure why??? except perhaps I was the only one with my own equipment? honestly, I think it's way simpler than that... he was panicked and didn't think straight and must have passed by at least two other people on the way to me. Perhaps, he developed tunnel vision and headed straight toward me without seeing anyone else to his side.

 

[shawrg]

I think you showed excellent judgement in all of your decisions concerning that OOA event. Including assisting him to the surface w/o a safety stop. The fact that the rescued diver was rated as a DM is very troubling. Hopefully his actions & behavior will be reviewed and addressed by the certifying agency appropriately.

 

[bowlofpetunias]

Oh and the question posted in regard to the DM passing by other people... I think he must have passed by others to get to me. Not really sure why??? except perhaps I was the only one with my own equipment? honestly, I think it's way simpler than that... he was panicked and didn't think straight and must have passed by at least two other people on the way to me. Perhaps, he developed tunnel vision and headed straight toward me without seeing anyone else to his side.

I think that is a reasonable assumption. Out of air? Where to you want to be... UP... you look up and in your field of vision is a diver with air in the direction you want to go = Tunnel vision.

Well managed N4C. Great reminder that a piece of paper or job title don't guarantee competence.

 

[lamont]

Looking back on this unfortunate incident I would like to get a better understanding of what actually should have happened in terms of a safety stop. Air permitting should we have done the stop for 3 minutes? Or was it the right thing to get to the surface right away when sharing a single tank?

How many minutes of gas did you and the DM have at 20 feet when you had 1500 psi? How many psi do you think you would be consuming per minute?

How many psi per minute would you be consuming on the surface for both of you, stressed?

How far off do you think your gauge is, when it gets near zero?

...

With an Al80, you had 38 cu ft of gas left at 1500 psi.

At 20 feet and a 2.0 combined SAC rate you would have been using 3.2 cu ft / min

You had around 12 minutes of gas at 20 feet, or were using 125 psi / min

At the surface you would have had 19 minutes of gas, or would have used it at a rate of 75 psi / min.

So, with 1500 psi, you could have stayed at depth for 3 minutes consuming about 375 psi of gas, to leave 1125 psi. At the surface that would 1125 psi would have lasted 15 minutes.

Even assuming that the last 500 psi of your tank could not be trusted you had 8 minutes of time at 20 feet until hitting that limit... or after doing a 3 minute stop at 20 feet, you had 8 minutes of gas left to sort things out at the surface before hitting 500 psi.

...

You had quite a lot of gas left, and gas goes very slowly at the surface or at 20 feet.

You still had enough gas left to do a safety stop and deal with a problem at the surface, even assuming gauge error.

How could you have communicated to the DM that you had enough gas and that you wanted to complete the safety stop? Probably the best idea is to simply show your gauge to the DM and then signal to 'level off' -- of course if the OOG diver still thumbs you at that point you probably have to assume some other kind of issue...

...

One thing you apparently did right was to get off the bottom promptly and not waste your gas futzing around deep and having your computer get annoyed at you at 40 feet was probably okay, provided that you could get your buoyancy together by 20 feet and arrest the ascent. That prompt ascent from the bottom set you up for having enough gas to complete the safety stop.

 

[Steve_Dives]

Well done.

FWIW, that little Rock Bottom hyperlink in Lamont's signature is a decent read.

 

[Walter]

I do not believe the rescue is done until the OOG diver is buoyant at the surface, and it may not be then, if he has any symptoms of AGE or other ascent-related issues.

The rescue isn't usually over until the victim is on the boat or shore and sometimes not even then.

 

[nuts4corals]

How many minutes of gas did you and the DM have at 20 feet when you had 1500 psi? How many psi do you think you would be consuming per minute?

How many psi per minute would you be consuming on the surface for both of you, stressed?

How far off do you think your gauge is, when it gets near zero?

...

With an Al80, you had 38 cu ft of gas left at 1500 psi.

At 20 feet and a 2.0 combined SAC rate you would have been using 3.2 cu ft / min

You had around 12 minutes of gas at 20 feet, or were using 125 psi / min

At the surface you would have had 19 minutes of gas, or would have used it at a rate of 75 psi / min.

So, with 1500 psi, you could have stayed at depth for 3 minutes consuming about 375 psi of gas, to leave 1125 psi. At the surface that would 1125 psi would have lasted 15 minutes.

Even assuming that the last 500 psi of your tank could not be trusted you had 8 minutes of time at 20 feet until hitting that limit... or after doing a 3 minute stop at 20 feet, you had 8 minutes of gas left to sort things out at the surface before hitting 500 psi.

...

You had quite a lot of gas left, and gas goes very slowly at the surface or at 20 feet.

You still had enough gas left to do a safety stop and deal with a problem at the surface, even assuming gauge error.

How could you have communicated to the DM that you had enough gas and that you wanted to complete the safety stop? Probably the best idea is to simply show your gauge to the DM and then signal to 'level off' -- of course if the OOG diver still thumbs you at that point you probably have to assume some other kind of issue...

...

One thing you apparently did right was to get off the bottom promptly and not waste your gas futzing around deep and having your computer get annoyed at you at 40 feet was probably okay, provided that you could get your buoyancy together by 20 feet and arrest the ascent. That prompt ascent from the bottom set you up for having enough gas to complete the safety stop.

very interesting stuff... thanks for sharing as it puts it into perspective. However, I think this info. is very helpfully after the fact as i don't think that i would have been able to do the math under the circumstances. Too many other things running through my mind.

As I was looking back on my computer log graph from the dive I could see that the first part of the ascend from moment of contact and share air began (@ about 78 feet) to 40 feet everything was going as good as it could be under the circumstances. Than at about 40 he began to fin or maybe simply was not releasing enough air from his BC??? I remember that I emptied a good majority of my air from my BC in order to try and slow the ascend a bit and even drooped into a lower position than he on the ascend. As for the air consumption, I guesstimated my SAC rate from previous dives and divided that time in two assuming he was breathing like I was and I knew still we probably had less time as he was breathing hard. Still I guesstimated that we would have enough air to do a safety stop for 3 minutes. However, as you've read he still wanted no part of the safety stop and I'm pretty sure I showed him my gauge but I don't know if he was really looking at it. I can tell you that he never reached over to check my gauge himself...

 

[Gombessa]

very interesting stuff... thanks for sharing as it puts it into perspective. However, I think this info. is very helpfully after the fact as i don't think that i would have been able to do the math under the circumstances. Too many other things running through my mind.

Check out the link at the bottom of Lamont's signature, as well as NWGratefulDiver's Gas Management article. It takes a while to process, but you can actually learn this, along with the shorthand calculations to figure stuff out underwater. For instance, I rarely try to do the math nowadays, but I know with an AL80 diving to 100fsw, I know that a full-blown gas emergency at depth requires about 1,600 psi in order to make a safe air-share ascent (so I need to start moving shallower before I hit 1,600psi). Knowing this also affects my willingness and planning to do certain deep dive profiles on AL80s and other small cylinders!

 

[nuts4corals]

perhaps I should post my dive log graph...