Turning air off after equipment assembly

[kelemvor]

Maybe this is taught differently in different agencies. I just looked it up in my naui scuba diver manual and it's covered explicitly on pp57-58. They instruct to do the checks, and secure the rig in the boat (or wherever you are diving). It doesn't explicitly say "don't turn it back off" but it is so verbose in the instructions that I find it hard to believe they intend for you to turn it off and then back on later in the process. I see that OP is PADI, does PADI cover the process explicitly in the manuals?

I guess it's like anything diving. There seems to be lots of disagreement on what the "right" things are to do. Perhaps in part because people must adapt to the situation, such as the cold mentioned by Tigerman.

 

[DevonDiver]

Don't you guys fill the bladder before jumping off a boat? If the air was off, wouldn't you notice the power inflator didn't work?

I was instructed air on, check your reg and octo. Check buddies reg and octo. Fill bladder, start breathing the reg before you enter and gitter done. Am I doing it wrong?

Absolutely... doing it right.

However, a pressurized, but turned-off rig will provide a finite amount of air once pressurized. Not enough to completely fill a bladder, but enough for the 'squirt' many people add. Same for breaths - a pressurized, but off, rig will provide 3 or 4 breaths... just enough to lull you into the water, but not necessarily enough to give warning of impending disaster. Far too few divers monitor their gauges/spg when check breathing - so there's a potential emergency just waiting to happen.

The fact is, proper pre-dive procedures and buddy checks should eliminate the chance of hitting the water with your tank turned off. The second, sad, fact is that far too few divers complete proper, comprehensive pre-dive procedures and checks. Thus, accidents happen.

Complacency is a big factor in the deterioration of pre-dive checks - as some divers gain experience, they get sloppy... stuff gets fast-forwarded or missed altogether. As per the comment:

"I always turn it off, after I turn it on... and we've been diving so long, we don't need to do Pre-Dive safety checks anymore"...

I've seen this attitude hundreds of times in customers/students. To me, it signifies a diver with sufficient experience to develop complacency, but insufficient experience to have had a 'reality check' about the inevitability of human error or dumb luck. Surprisingly, it is very frequent at dive pro levels. Again, the fact is... we all make mistakes occasionally, regardless of experience or certification level.

This is illustrated by the number of times you'll see kitted-up divers (ready to enter the water) discover their air is off at the last moment. "Hey buddy, can you turn my air on for me", just before they step off the boat. There's no excuse for that, but it happens all too frequently.

Complacency can really get out of hand. I once had to do a rescue (throwing assist) for a very experienced (500+ dives, BSAC Sports/PADI Rescue) diver who skipped buddy checks (too cool for school) and jumped into the water with BCD deflated, fins in his hands and mask around his neck. No buoyancy at the surface...no fins, no mask, no air in regulator..panic occurred near instantaneously.

Complacency was why I had a near-emergency also. I was very busy running Open Water class for 4 students. My focus was on supervising them, at the neglect of myself. I needed to enter the water first and check conditions. Slung my kit on quickly, hopped into the water intending a quick negative entry/descent to get down and confirm viz/current, before my students entered. Got down to ~8-10m depth before my air stopped.

As mentioned, I am a technical-qualified diver, so ingrained reaction was to reach back and turn-on the air. Countless hours of doubles 'valve drills' permitted that response - a recreational diver without that ingrained training shouldn't assume they'd achieve the same. If it weren't for that reaction... I was alone, at depth, negatively buoyancy and sincerely in need of air. I could have died.

Again... fact is... I had done several thousand dives at the time. My experience, skills and knowledge were well above average. I'd always 'caught' being turned-off before. I'd never recognized that relying on last-moment checks or discoveries were the final barrier against a potentially lethal emergency occurring. I had enough warnings ("Hey buddy, can you turn my air on for me"), but never recognized those warnings for what they were - a sign that my protocols were failing. It was sufficient to rely on those last checks... the inflation of my BCD, those few breaths from my reg during entry... to keep me safe. Eventually, Murphy's Law caught up with me... a circumstance happened where I didn't inflate the BCD or take enough breaths... and it caught me out.

The lesson being... 'getting away with it' once, twice... a dozen... a hundred... times is not acceptable. Sooner or later luck and circumstances won't intervene and Mr Murphy will come to bite you in the ass... potentially fatally.

 

[GrumpyOldGuy]

Its not about hitting the hot o-ring with 3000 psi, its about the fact that heat will make air expand, which again will increase the already high pressure..
An air AL80 can show 250-260 bar (3600 to 3800 psi) on the deck when you turn it on. If you submerge it for 10 minutes it'll drop to 200-210 bar (2900-3050 psi)..

Really, this IS a real issue if you go diving in Egypt and dive ops cover this in their "on the way to the jetty" information, yet it happens EVERY day that someones tank goes *POP*HIIIIZZZZZZZZZZZZZZZZZZZZZZZZ* because they forgot to depressurize

Exactly, you turn it on (with the extra pressure) BEFORE you hit the water and it cools it down. So its the same high pressure, just for a shorter duration (a few minutes) vs the length of the boat ride.

Do O-rings go while on the boat ride? Yes of course. The question is would the o-ring that you save by removing the pressure pop anyway when you turn the valve on just before your dive? Or worse pop just after you splash?

On more thought. In general, if you are going to test a system, you don't test it at or below the working limit, but at a level slightly above the working limit. Your method might extend the life of the o-ring a bit, but your not doing a very good test of the o-ring integrity either. My preference is the best possible test and replace the o-ring if it fails, they are cheap and I carry spares.

 

[spectrum]

Don't you guys fill the bladder before jumping off a boat? If the air was off, wouldn't you notice the power inflator didn't work?

I was instructed air on, check your reg and octo. Check buddies reg and octo. Fill bladder, start breathing the reg before you enter and gitter done. Am I doing it wrong?

Take it beyond the boat.... Plenty of us a mainly shore divers. It's my practice to enter the water with a substantialy full BC bladder so if the surf rolls me or I trip I bob like a cork. If the surf's up I'll have my regulator in my mouth. I do see plenty of buddys that don't load the BC or even draw a breath until thumbs down.

Even on a boat, make it a wing that does not hug you, muffled with a heavy hood, hustle and excitement and the cue of a non responsive inflater can be missed.

There is a reason they call them accidents.

Pete

 

[CamG]

I gear up the same way follow the same mantra whether on a boat or from shore.
Between dives tanks get shut down no air loss risk. Stage bottles to.
Valves are checked pre-dive before donning, I don the rig test breath each reg before I put fins on to enter the water.
I can do and train valve drills on most dives while performing deco / safety stops.
While I understand leaving valves on, I do not practice this.
My style of diving doesn't require it I have been trained other techniques to ensure my air is turned on pre-dive.

CamG

 

[Tigerman]

Exactly, you turn it on (with the extra pressure) BEFORE you hit the water and it cools it down. So its the same high pressure, just for a shorter duration (a few minutes) vs the length of the boat ride.

Do O-rings go while on the boat ride? Yes of course. The question is would the o-ring that you save by removing the pressure pop anyway when you turn the valve on just before your dive? Or worse pop just after you splash?

On more thought. In general, if you are going to test a system, you don't test it at or below the working limit, but at a level slightly above the working limit. Your method might extend the life of the o-ring a bit, but your not doing a very good test of the o-ring integrity either. My preference is the best possible test and replace the o-ring if it fails, they are cheap and I carry spares.

I never suggested turning the tank on after you go in, I suggested turning the tank on and checking you have air and then turn off and DEPRESSURIZE the system. 2 minutes before jump time is not the time to find out you geared up on a half used or empty tank..

The point I was trying to illustrate with the very specific example of air readings was just how much of a difference that temprature makes. When it makes that much difference in a larg container, imagine what it does to a smaller, more easilly heated one..

No, generally the o-ring you dont blow by depressurizing dont blow when you turn on the tank just before you jump - unless of course you skipped attaching and testing the first stage when setting up the rest of the gear - then you can bet your ass skipping that part is gonna bite you in the ass and make everybody wait while you fix it..

On a 200 bar tank (which it'll drop back to not long after you splash) 250 bar is already WAY above working pressure, why would you need to let it sit and heat up more, pressurized to "test your o-rings" thats gonna blow just as much if theire brand new in those conditions?

Blowing the o-ring just after I splash would be fine, when youre 15 minutes into the dive and down at 20-30 meters its kinda inconvenient...

 

[Ayisha]

My reg doesn't leak air and it seems to me the most extreme inconvenience is that I will have to replace an o-ring, which I have to do about 25% of the time on a rental tank anyway!

Or quite possibly lose a dive if there aren't any other full tanks around. I've seen o-rings let go several times when tanks have been left on during long rides, and it's amazing how fast they empty.

I also turn the air off and purge the lines if I'm not using the rig pretty soon. When I go to put on my gear, the first thing I do is turn the air on and continue from there. If I'm waiting to go in for a while longer or if a DM checks my air, I'll reach back and ensure that the air is on or breathe while watching the pressure.

 

[MXGratefulDiver]

Maybe this is taught differently in different agencies. I just looked it up in my naui scuba diver manual and it's covered explicitly on pp57-58. They instruct to do the checks, and secure the rig in the boat (or wherever you are diving). It doesn't explicitly say "don't turn it back off" but it is so verbose in the instructions that I find it hard to believe they intend for you to turn it off and then back on later in the process. I see that OP is PADI, does PADI cover the process explicitly in the manuals?

I guess it's like anything diving. There seems to be lots of disagreement on what the "right" things are to do. Perhaps in part because people must adapt to the situation, such as the cold mentioned by Tigerman.

There's no "right" or "wrong" in this case ... there are trade-offs each way. What agencies teach at the OW level doesn't go into detail on the trade-offs ... it's designed instead to give you a routine to follow that will be "safe" in all cases.

If you leave the air on you will have less risk of entering the water with your valve turned off and greater risk of losing air through a leaking connection before entering the water

If you turn the air off ... vice versa.

It really is that simple.

Setting up for a dive is a really routine oriented activity. What matters is finding a routine that works for you and sticking with it. That applies regardless of how often you dive, or how experienced you might be, because we're all human and humans occasionally make mistakes. A routine improves the odds of catching yours before you put yourself underwater, where it can quickly turn a minor mistake into a significant problem ...

... Bob (Grateful Diver)

 

[brnt999]

Something that happened to my brother is he was diving with a group off a cruise ship. The last thing that happened before he jumped in the water is they did a buddy check, and his buddy turned his air off and turned the valve back on a quarter turn so he was getting air from his regulator. After he started descending it got harder and harder to draw air and he signalled his problem to the DM who turned his air on. I have since read other occurances of this happening. So after you do a buddy check you should check that your buddy didn't screw something up.

 

[chillyinCanada]

Brnt, that's why one takes the three quick breaths while looking at the guage. The needle holds steady without fluttering or dropping and you are good to go. Some say it needn't be three breaths but for me that's minimum. Guess what happened the time I forgot that check before I rolled? Yes, of course, air not on. I was fortunate to be about 5-6' down and not 30' like devondiver. Sea was very calm, so I was able to safely ascend and back up to the boat. The captain reached down and turned it on.

But even if one does that check without fail, one is still open to making a mistake. A couple of weeks ago, so intent was I on watching my needle that I neglected to note that my tank wasn't full. I was at depth before it clicked. Still managed to get in a complete dive but it certainly wasn't all that it could have been. Fortunately, no one made me buy all the beers for getting back on the boat with a lot less than 500 psi.