Shutting off a single tank diver's air supply in a free-flow?

[Dtaine]

This thread:http://www.scubaboard.com/forums/accidents-incidents/265854-what-would-you-do.html gave me a question, which I feel is better suited in this forum, I debated putting it in Advanced.

In a free-flowing regulator situation between two single tank divers, is it really a good idea to do as some in the other thread suggested and shut off the free-flowing diver's air supply once he/she is breathing off one of your second stages?

I can't think of any real benefit for doing so unless it's in an attempt to see if the free-flow is solvable at depth. If the free-flow is unable to be fixed, or if the diver with the free-flow just wants to call the dive and not bother with trying, I'd be hesitant to shut off his/her air supply in case of possible separation on the way to the surface.

One of the reasons mentioned for turning off the free-flowing air source was to prevent a possible auto-inflation of the diver's bcd, but wouldn't it just be safer to disconnect the inflation hose? After all, you and the buddy are ascending so there's no need to add air to the bcd anymore.

Another reason for turning off the air was that the bubbles from the free-flow would no longer be distracting. I'd like people's opinion as to whether they believe the benefit of losing the bubble distraction (obviously this would vary depending on the size of the free-flow), outweighs the risk of separation and the diver being unable to turn his/her air-supply back on.

Now while I do believe all divers should be able to manage their valve(s) underwater, I'm betting there are plenty who can't. Also, just to state the obvious, this question revolves around a scenario well within NDL limits, which obviously means a CESA is possible if buddy separation (with the one diver's air-supply off) occurs on ascent.

Just looking for people's thoughts and input - I don't have any of my dive materials at hand to double-check the standard procedures taught to OW students.

 

[Lucy's Diver]

Why bother adding a task to an emergency situation? I also can't see how a free flow reg could possibly cause a stuck open power inflator (if this is what you mean by "auto inflation"). Also as the tank free flows its getting more bouyant, not a bad thing under the circumstances.

 

[JahJahwarrior]

Shut down the valve, then turn it back on to see if that solves the problem. If it does not, it would be my inclination to leave it on, and have the diver breathe off of his own tank for as long as possible, then switch to his buddy's regulator.

Auto inflation is not a concern unless the BC power inflator valve fails.

OW divers who cannot reach their own valves or remain calm in a free flow situation should think long and hard before getting back in the water. Panicking underwater can kill a diver and their buddy.

That said, it is possible that a diver would be stressed by having to monitor their air as the regulator freeflows, and switching immediately to a buddy's gas supply and shutting down their freeflowing regulator might be best to keep them calm.

As far as buddy seperation goes, OW classes are taught to maintain contact: both divers holding on to the other's BC: buddies sharing air should not be able to be seperated if they employ this tactic.

The above is simply my opinion and as you can see by the fact that I present reasons for both options, what is important is getting to the surface alive, and if you have to do it some "unfavorable" way, that's fine. Just think long and hard before putting yourself underwater again if this happens and you do not respond well to the "emergency" situation: living is more important than diving

 

[Web Monkey]

In a free-flowing regulator situation between two single tank divers, is it really a good idea to do as some in the other thread suggested and shut off the free-flowing diver's air supply once he/she is breathing off one of your second stages?

If it's a cold-water freeflow with two equally-equipped divers, shutting off the freeflow and sharing air is almost always a bad move because you would now have one OOA diver (the one you shut off) and another freeflow for the donor due to the increased airflow though the second stage. (edit: should read "first stage")

Terry

 

[Notso_Ken]

How about shut off the free fowing tank, and switch to a redundant (not your buddies) air supply? 40cf pony, sling tank, etc?

Also, no reason the diver with the free flow couldn't breathe off the free flow for a little while on the way up, until the pressure gets low, then go to the redundant air supply (and, no I don't think 2 - 3 cf is enough to qualify as a "supply".)

Ken

This thread:http://www.scubaboard.com/forums/accidents-incidents/265854-what-would-you-do.html gave me a question, which I feel is better suited in this forum, I debated putting it in Advanced.

In a free-flowing regulator situation between two single tank divers, is it really a good idea to do as some in the other thread suggested and shut off the free-flowing diver's air supply once he/she is breathing off one of your second stages?

I can't think of any real benefit for doing so unless it's in an attempt to see if the free-flow is solvable at depth. If the free-flow is unable to be fixed, or if the diver with the free-flow just wants to call the dive and not bother with trying, I'd be hesitant to shut off his/her air supply in case of possible separation on the way to the surface.

One of the reasons mentioned for turning off the free-flowing air source was to prevent a possible auto-inflation of the diver's bcd, but wouldn't it just be safer to disconnect the inflation hose? After all, you and the buddy are ascending so there's no need to add air to the bcd anymore.

Another reason for turning off the air was that the bubbles from the free-flow would no longer be distracting. I'd like people's opinion as to whether they believe the benefit of losing the bubble distraction (obviously this would vary depending on the size of the free-flow), outweighs the risk of separation and the diver being unable to turn his/her air-supply back on.

Now while I do believe all divers should be able to manage their valve(s) underwater, I'm betting there are plenty who can't. Also, just to state the obvious, this question revolves around a scenario well within NDL limits, which obviously means a CESA is possible if buddy separation (with the one diver's air-supply off) occurs on ascent.

Just looking for people's thoughts and input - I don't have any of my dive materials at hand to double-check the standard procedures taught to OW students.

 

[Dtaine]

How about shut off the free fowing tank, and switch to a redundant (not your buddies) air supply? 40cf pony, sling tank, etc?

Also, no reason the diver with the free flow couldn't breathe off the free flow for a little while on the way up, until the pressure gets low, then go to the redundant air supply (and, no I don't think 2 - 3 cf is enough to qualify as a "supply".)

Ken

Well the entire scenario that I asked the question around is two single tank divers without any other air supplies than the two tanks.

Edit: that could've been made clearer in the OP

 

[Nemrod]

There is no reason off hand you would turn the air off on a free flow on a single tank no deco dive.

N

 

[dumpsterDiver]

I've seen two different people recommend shutting down a single tank freeflow. For a typical recreational diver, this is not a smart thing to do. Why not initiate an immediate ascent with the diver breeathing from the free-flow? If the diver is too nervous, then they can breath from the octopus. Assuming the buddy comes up with them.

What happens if you shut the valve down, the divers become separated and the diver can not reach his tank valve? Then, you might end up killing the diver by shutting down their life support, eliminating their ability to add air to the BC all due to a relatively minor problem.

The answer for tech divers who have redundant air supplies or who have incurreed a deco penalty, then the benefit to preserving the air and doing a shut down would seem to be different.

 

[John_B]

I look at this another way after experiencing this situation first hand.

On a single tank cold water dive, my buddies first stage froze "open" at the bottom of the initial descent and started a pretty spectacular freeflow. I passed him my primary, I went to my backup, exchanged OKs, we checked both pressure gauges, exchanged OKs, he made the "shutting down my valve" signal and shut down his own valve (I could've helped but didn't need to). We did a slow ascent (rock bottom meant we had plenty of gas) and after a long couple of minutes we tried the valve again and it had de-iced and was functional again. Scary experience the first time it happens, but we both knew what to do.

Analyzing the dive we came up with a few items to correct. First was technique, he shouldn't have laid on the inflator to slow his descent in cold water, short bursts work better. Second was equipment, he got rid of his piston first stages and replaced them with sealed diaphragm first stages. Third was configuration, this type of a dive should probably be done in doubles or with two first stages. The one mistake we didn't make: we both had a solid dive buddy we could count on.

Would I shut down my own valve if I was diving with an instabuddy instead of a regular buddy? I don't know, I probably wouldn't do that cold water dive with an instabuddy anyway. Being on the same page with a buddy that you've practiced drills with is worth its weight in gold.

When you guys say you wouldn't shut off the valve, what I don't get is why you would just let the tank empty? What good does that do you? Sure as a last resort you can breathe of a freeflowing regulator on your way to the surface, buy why would you if you didn't need to? I wonder how many of you have actually seen the volume of bubbles that are generated when both second stages are dumping gas? How many know how fast that will empty a tank?

In the end, you can't really fix the problem of choosing the wrong buddy on the surface once you are underwater and the stuff hits the fan. In my mind, that makes all the difference in what options you have to solve problems underwater.

My two cents. Obviously YMMV.

 

[John_B]

I've seen two different people recommend shutting down a single tank freeflow. For a typical recreational diver, this is not a smart thing to do. Why not initiate an immediate ascent with the diver breeathing from the free-flow? If the diver is too nervous, then they can breath from the octopus. Assuming the buddy comes up with them.

What happens if you shut the valve down, the divers become separated and the diver can not reach his tank valve? Then, you might end up killing the diver by shutting down their life support, eliminating their ability to add air to the BC all due to a relatively minor problem.

Why would you leave your buddy in that situation?

Why would any diver not be able to reach their valve?

If its the the first stage that freeflows, both second stages are going to be dumping gas. What are they going to do once the tank is empty?

As I said before, the quality of the dive buddy has a lot to do with what options you have.