How do divers not realize their air isn't on?

[Soloist]

Oh boy, I've got 3 questions...

1.) Why do folks turn their air off on the boat? I can understand folks who use transmitters, because they don't want to run the battery, but for folks who don't use them, is there a point? And I've also heard that some DM's turn the air off -- WHY would they do that? Especially without telling the diver??

2.) You still had 3600 psi on your gauge even after turning the valve off? Did it read that simply because you didn't purge all the air?

3.) Does surfacing to turn off the air mean it's difficult to do underwater, or just that it would take too long to do and you would be sinking too much while turning it off?

Oh, actually a 4th question:

4) WHY DID MY INSTRUCTOR NEVER TEACH ME ANY OF THESE QUESTIONS?

1) I hate that sickening sound of a regulator free flowing on the deck because someone bumped into it or if you are in “sporty” seas and something else happens, so I turn my air off at the valve and purge the system until I am ready to dive. You can prevent most free flows by turning the adjustment knob to limit air flow, if your reg has that feature, but I do both out of habit.

2) Yep, the reg was still pressurized between the first and second stages even though the tank was off.

3) No difference in turning the tank valve at 100 feet down or on the surface. I just instinctively headed for the surface in case I couldn’t fix my screwup on my own.

4) I think most instructors assume you will dive with your tank valve open. What do they know?

 

[Soloist]

A-HA! That is a good idea. I might start putting my tank higher from now on.

Realize this will affect your trim because you are shifting weight. Not dramatically, but just be aware.

 

[M DeM]

1) I hate that sickening sound of a regulator free flowing on the deck because someone bumped into it or if you are in “sporty” seas and something else happens, so I turn my air off at the valve and purge the system until I am ready to dive. You can prevent most free flows by turning the adjustment knob to limit air flow if your reg has that feature, but I do both out of habit.

2) Yep, the reg was still pressurized between the first and second stages even though the tank was off.

3) No difference in turning the tank valve at 100 feet down or on the surface. I just instinctively headed for the surface in case I couldn’t fix my screwup on my own.

4) I think most instructors assume you will dive with your tank valve open. What do they know?

Thanks for the answers! They all make sense now!

 

[M DeM]

There are several reasons for a negative entry, but I’m not aware of air consumption being one of them. When DRIFT diving in seas with a current your entry will be dramatically affected by the strength of the current. If you are trying to hit the beginning of a wreck or a very specific spot on a reef the current has to be factored in as part of your descent. The captain will account for the current and drop you an estimated distance in front of the target, so you have a limited window to get to your dive location. If you don’t get down quickly enough you will simply blow past your target. Another reason is when hunting it’s always good to be first! So a negative entry with a dash to the bottom can be rewarding. Yet another is to simply get to the bottom where the current is typically not as strong. I always do a negative entry unless the boat demands otherwise. It’s somewhat tedious bobbing up and down on the surface waiting around for everybody to go down together.

makes sense!

 

[The Chairman]

Why do folks turn their air off on the boat?

I certainly don't, but if I did, I would vent the system.

WHY DID MY INSTRUCTOR NEVER TEACH ME ANY OF THESE QUESTIONS?

You might want to ask your instructor that question. I vividly remember two classes for kids. I always invite their adult to be a part of their class with the kid's permission. Why? I want them to understand why I trained their kid the way I did, so that they don't go breaking good habits with bad ones. The first one was at Blue Spring, where we were going to do the first two OW dives. The dad hadn't been able to be in the pool with us and we're in waist deep water doing our final buddy checks. "Dad, I didn't hear you breathe. Can you breathe for me?" "What", She repeated the question. "Why do you want to hear me breathe?" "Then I know that your air is on." It wasn't. Proud of her for that, I turned his air on. "We ready?" He asked. "No. Please let me hear you breathe." He breathed. "While watching your SPG." I explained why and at this moment he was pissed. No, not at me, but at his OW instructor. A few weeks earlier he dove off of a boat with his air off. Never knew he should have heard his buddy breathe. Never knew to look at his SPG. That was over a dozen years ago. Two years ago, I had almost the same scenario, except it was a son and his dad. The dad had his lesson at the side of the pool. He was also pissed and again: not at me.

You can make your buddy check as detailed and formal as you please, or far, far less so. Just be sure that you hear your buddy go through the breathing process. No weights, no mask and no fins are all laughable, but no air can be tragic as the OP has pointed out. Asking your buddy if their air is on doesn't really count. They might remember wrong. Make sure you HEAR them breathe. You can assume that they are looking at their SPG, if that's the protocol you both use. Just make sure you hear them do it. OK, if they think they've already breathed it, they can do it again for you. Two breaths won't affect your bottom time.

 

[gypsyjim]

Good point @Soloist about shifting the tank up with left hand!

Exactly.

 

[gypsyjim]

schitt is going to happen. Learn and practice resolving issues, before the stinky stuff hits the spinny thing

 

[Soloist]

Thanks for the answers! They all make sense now!

“I turn my air off at the valve and purge the system”

Please understand I do NOT recommend you are anyone else follow this procedure. I am simply describing what works for me. For the reasons stated earlier, I prefer to have my tank off and the system purged. Then open the valve just prior to the dive. You have to decide what works best for you.

 

[The Chairman]

Please understand I do NOT recommend you are anyone else follow this procedure.

It's OK. The main thing is that you and your buddy are consistent in your pre-dive mantra. Changing things up all the time is where we run into trouble.

 

[KenGordon]

Hi folks-

I've been told two sad stories about deaths which happened because the diver neglected to turn their air on.

One was with a rebreather, but I think the other one was just open circuit. I'm just wondering how this happens given that..

You enter the water with your regulator in -- can you not tell that there's no air?
What about your BCD? I guess that means there's no air whatsoever in your BCD when you enter?
Why can't you swim back up to the surface when you notice?

The divers in both situations were suuuuuuper experienced. I ask not because I'm criticizing them, but to find out if there's a way that *I* might not recognize it (assuming my buddy also failed to recognize it.)

Is there air "leftover" in the regulator hose that would cause you to have a tiny bit of air before you realize the cylinder isn't open?

Navy officer, 35, dies in off-duty diving mishap

People make mistakes. So sometimes the mistake will be to not have your air on. Skilled divers are not the ones that can reach back and turn their air on once they are in the water, skilled divers are those that follow the process and spot the mistake before jumping in.

BTW, people turning off gas, my transmitter stops using power when the pressure stops changing. So, so if I look at a dive where I change s from backgas to deco gas the trace of backgas pressure goes away.

Personally I purge a regulator once the gas is off to try to avoid thinking it is on when it is not.