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Author Topic: What are the causes of Out Of Air (OOA)  (Read 6672 times)

poh6702

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What are the causes of Out Of Air (OOA)
« on: 10 Nov 14, 09:54 »
Branching out from the other thread about Double tank, Spare Air and Pony Bottle; people who carry these extras are to ensure that in OOA situation, at least can still get to the surface as safe as possible. As divers, we don't want to get hit by OOA, that is why we maintain our equipment, check our pressure gauge regularly, stick to our buddy when diving.

I would like to classified then in 3 categories for discussion:

1. Due to carelessness: Used almost empty tank and forget to ensure pressure above 180Bar, turn the valve in wrong direction (turn to close then open quarter turn), dive too deep (or due to strong current) and forget to check pressure. Any others?

2. Equipment failure: what are the likely cause? and what is the best way to react?

3. Disaster: what can happen? How to react?

I am a kiasi diver, hope to understand the causes and be able to avoid it as much as possible. Of cause pairing with buddy is the best solution to overcome when OOA happen.

Dive safe, dive KiaSu and dive KiaSi.

Alvin Ho

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Re: What are the causes of Out Of Air (OOA)
« Reply #1 on: 10 Nov 14, 10:45 »
In now my 16th year of diving, i have had 2 near OOA situations, both my fault.

1) Shallow dive at Puri Jati in Bali. We were in water for 140min already and i was about to exit the water with about 5-10 bar left in tank when those who exited already shouted that the guide found something special. i finned over and went down to find a frogfish so i started shooting again. It was shallow depth of maybe 5-7m. After shooting a bit i found the breathing a bit hard and knew the tank was empty so i slowly surfaced.

2) During a dive photography competition in Cebu, there was a dive in pretty strong current that made photography difficult, i was shooting wide angle while others were shooting macro. I finished what i wanted to shoot so decided to help out others shooting macro. I checked my gauge and i had about 30 bar left. Thinking i had enough though it was about 15m, i went to help a friend. After helping i checked my gauge and it showed empty. I went over to my then gf to signal to her to ascend as i was still breathing normally. Halfway through our safety stop my reg again was sucking on empty so i got my gf's octo to complete the stop.

One last incident wasn't close to OOA but it wasn't that wise decision in retrospect.

I had a leaking hose/gauge/octo (can't remember) on a dive at lembeh. could hear the hissing on the surface but it didn't seem that loud or leaking that bad. But as i descended the leaking got worse. So i did a quick calculation and went to shoot the subjects at the site v quickly, spending 5min max on each subject and checking my gauge constantly. I finished my tank in about half the time i normally dive and the whole dive lasted only about 40min.


I would say most OOA situations are due to diver error. equipment failure is seldom the issue when you read dive accident reports.

Personally as a photographer i find myself diving alone quite often or find myself alone when a dive group has moved on. During such situations i find myself adjusting my dive plan to be a lot more conservative. I go shallow and i don't dive as long as i normally do. Not advocating anything but it's just the way i dive.
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Chris

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Re: What are the causes of Out Of Air (OOA)
« Reply #2 on: 10 Nov 14, 11:49 »
I would say most OOA situations are due to diver error. equipment failure is seldom the issue when you read dive accident reports.

I could not agree more. It is typically a combination of carelessness (as in "50 bar is for beginners, I am sooo experienced i can easily max it out to ten") in combination with something unexpected happening when you already pushed the limit. This can be anything from a bit more current than anticipated to getting distracted by something nice (especially as a photographer).

Ryoin82

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Re: What are the causes of Out Of Air (OOA)
« Reply #3 on: 10 Nov 14, 13:11 »
I think the main consideration for newbie divers will be failing to check spg regularly. Being too fascinated or trying to catch up with dm diverts their attention. There are plenty of cases where divers only Check pressure when prompted by dm, only to realize they have 20 bar left.

Could peer pressure or ego be another factor as well? U are down to 50 bar but don't want to sound out becoz u don't want to be the one to end the dive.


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poh6702

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Re: What are the causes of Out Of Air (OOA)
« Reply #4 on: 11 Nov 14, 09:36 »
I have seen burst O-ring (tank valve) while setting up gear on boat, I am curious to know whether has anyone encountered burst O-ring while diving? Logically that should not happen, because if the O-ring doesn't burst while the pressure is at the highest point, while diving, the tank pressure reduces and the water pressure is higher than on the boat, that should not happen, but in real world, has it happened before? Likewise for burst disc?

I was told (can't remember who) that regulator design is in such way that, should it fail, it only free flow, but will not have no air supply situation, is this true?

Chris

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Re: What are the causes of Out Of Air (OOA)
« Reply #5 on: 11 Nov 14, 10:35 »
I was told (can't remember who) that regulator design is in such way that, should it fail, it only free flow, but will not have no air supply situation, is this true?

I believe what you are getting at is the second stage design: All but one manufacturer use "downstream" valves which if they break should be in "open position". An upstream valve does the opposite and might be jammed close instead. But as you said - the only logical time the valve breaks is when you open your tank on the dive deck. The only brand I know using upstream valves is Poseidon and I am sure there is some reason for their design... never cared as they are out of my budget anyway.

antacid

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Re: What are the causes of Out Of Air (OOA)
« Reply #6 on: 11 Nov 14, 12:50 »
had a dive where one of the divers had a burst O-ring underwater. Happened on the descend so maybe around 5 minutes into the dive? Funny thing was, the diver didn't even know what happened and was wondering why everyone was crowding around her and pushing octopuses in her face. haha

aloe

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Re: What are the causes of Out Of Air (OOA)
« Reply #7 on: 17 Nov 14, 09:06 »
yah, i did.. It burst onboard... replaced... then when descending, it burst again underwater. I felt and heard the bubbles.... reached behind to feel and could feel the bubbles as well. Signalled to my buddy that I'm ascending but I think she din realise. LOL! In the end, the DM came up to look for me when I was already onboard the boat. Told him i will abort dive.

It's a sign (to me) when the O ring burst twice onboard and while descending. So decided not to risk it.. =X

Solid_jim

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Re: What are the causes of Out Of Air (OOA)
« Reply #8 on: 17 Nov 14, 22:43 »
divers who are dreaming lol or got nut
Dunno why so many boliao people
eat too full
post bo liao things

BareBear

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Re: What are the causes of Out Of Air (OOA)
« Reply #9 on: 18 Nov 14, 13:41 »
I think it happens due to:
1. A lack of situational awareness. This is probably the most common cause (i.e. not checking the SPG, not knowing how much air you have left at all times).
2. Buddies not working well as a team / buddies with poor situational awareness. If an LP hose happens to blow underwater, the gas in the tank could drain very quickly. If a buddy is not within sight and paying attention, it could end badly.

2. Inadequate dive protocols/training.
- The SPG is inaccurate at extreme ranges, especially below 40bar. It would be better to call the dive at 40bar regardless of depth.
- The concept of minimum gas is not widely understood. This is the amount of gas that will get you and your buddy to safety doing all necessary stops along the way, should one diver have an emergency situation. "Surfacing at 50bar" is inadequate if you are diving to 30m.
- Doing bubble checks before descending is not commonly practiced among divers here. Thus if you do have equipment that is in early stages of malfunction, it goes undetected until things get more serious. This is an important drill as I have personally detected bubbling from the SPG, first stage body, hose connections, tank valves and rear dump valves that were quickly fixed because they were detected early. At minimum, you are aware you have a minor problem and you have the option to continue but be watchful if the leak is minor, or call the dive if it is more serious.
- Doing a flow check and being able to reach your valves should be mandatory whether diving in single or double tanks. In this way, if you are in doubt, you can always reach back and check your valves.

« Last Edit: 18 Nov 14, 13:43 by BareBear »