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Author Topic: What are the causes of Out Of Air (OOA)  (Read 5920 times)

poh6702

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Re: What are the causes of Out Of Air (OOA)
« Reply #10 on: 18 Nov 14, 16:38 »
One habit I always do is immediately after setting up the gear, open the valve to check to ensure pressure is more than 180 bar, then turn off the valve to see whether the pressure gauge drop or not within few seconds, if one has a leaking system, the pressure gauge will drop very fast, if the needle can stay without dropping, at least you are sure the system is not leaking from the start. Of course if the leak will to happen after getting into water, then will need to react according to situation.

runez

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Re: What are the causes of Out Of Air (OOA)
« Reply #11 on: 18 Nov 14, 17:12 »
One habit I always do is immediately after setting up the gear, open the valve to check to ensure pressure is more than 180 bar, then turn off the valve to see whether the pressure gauge drop or not within few seconds, if one has a leaking system, the pressure gauge will drop very fast, if the needle can stay without dropping, at least you are sure the system is not leaking from the start. Of course if the leak will to happen after getting into water, then will need to react according to situation.
Just remember to turn your valve on again before the dive! Or it'll become a self-inflicted OOA situation.. Haha..

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DIN

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Re: What are the causes of Out Of Air (OOA)
« Reply #12 on: 18 Nov 14, 17:28 »
Just remember to turn your valve on again before the dive! Or it'll become a self-inflicted OOA situation.. Haha..

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This reminds me of a story in Maldives... an Italian lady who was overweighted, descended with her valve off. She probably couldn't swim up to the surface because of her weight. They found her body at 50m.   :(
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poh6702

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Re: What are the causes of Out Of Air (OOA)
« Reply #13 on: 19 Nov 14, 00:01 »
This reminds me of a story in Maldives... an Italian lady who was overweighted, descended with her valve off. She probably couldn't swim up to the surface because of her weight. They found her body at 50m.   :(
Yeh! really anything can happen if one don't follow protocol! We also guilty our self because I believe most of us don't practice buddy check before jumping into the water. But luckily is that at least one should try to pump up the BCD and put the second stage into mouth and breath from regulator before plunging into the water, isn't it? And such problem should be detected. I did have a few times forgot to turn on the valve when getting ready to get into the water, but realized it when not able to pump the BCD

antacid

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Re: What are the causes of Out Of Air (OOA)
« Reply #14 on: 19 Nov 14, 17:59 »
on the boat when you turn off your air, it's always a good habit to make sure to purge so that the SPG shows zero. So when you do your pre-dive checks, you will know if your air is turned on or not. 

people usually set up their equipment, leave it for a long time, then come back to gear up and jump in. it can get chaotic and messy if it's a small boat, and if you just glance at your SPG to check your air, you're going to be in for a big shock underwater.

1. purge regulator immediately after turning off your air.
2. when checking your air before jumping in, always breathe/purge the regulator while looking at your SPG.

Cool79

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Re: What are the causes of Out Of Air (OOA)
« Reply #15 on: 25 Nov 14, 02:31 »
Normally I will start to ascend when I hit 50 bar. U need to know how is your air consumption too, then u can gauge how much air is required for you to safely end the dive.

Normally when I am ard 20-30 m, 50 bar I will ascend. If I am at 30-40m, I will start to move up when I have half tank of air. U never know sh*t happens.

alvlim

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Re: What are the causes of Out Of Air (OOA)
« Reply #16 on: 25 Nov 14, 15:53 »
Feel that its not a good practice to accent when hit 50 bar. accent should be at about 80 bar min so that even after safety stop and ended the dive, there will still be 50 bar left.

runez

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Re: What are the causes of Out Of Air (OOA)
« Reply #17 on: 25 Nov 14, 21:37 »
There are loss of gas situations, and then there are out of air (gas) emergencies. The former need not develop into the latter unless multiple things go wrong at the same time.

I feel that complacency would be the cause of many OOA emergencies, like the complacent diver who:

- did not check his SPG regularly because his previous (insert number here) dives were uneventful, and because he never ran out of air before.

- went deeper than than his training and got narced without knowing it

- no longer did pre-dive checks

- no longer bothered to stay close to his buddy

- went into an overhead environment without training just because he had (insert larger number here) successful open water dives before.



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snikrs

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Re: What are the causes of Out Of Air (OOA)
« Reply #18 on: 25 Nov 14, 22:15 »
With regards to surfacing with or starting to ascend with 50 bar -

I think it's more than just a good practice to plan ahead and learn "rock bottom gas management" than to simply surface at "50 bar" of gas. In most cases, 50 bar is sufficient to complete a proper ascent with a safety stop, but just simply isn't safe enough, in my opinion.

Let's say a diver has an average Surface Consumption Rate (SCR) of 20L/min, and diving a single 11L tank (80AL), as commonly found in our region. Assuming the diver is at a depth of 30m, and ascending at 9m/min, it would take him about 3 minutes to reach 5m. For the sake of conservativeness (and simplicity in calculation) the ambient pressure is assumed to be a constant 4ATM for the ascent. That journey from 30m to 5m alone will require approximately 20 bar (For the math nut: (20L/min X 4ATM X 3 minutes) / 11L ≈ 22 bar). The safety stop will require approximately another 10 bar (Assuming constant ambient pressure of 2ATM, (20L/min X 2ATM X 3 minutes) / 11L ≈ 11 bar). That's a total of 30 bar from 5m to 30m, without incidence.

In the case of a stressed diver, SCR can easily escalate to 30L/min, and what if he happens to be sharing gas with a buddy? That would mean a total of 60L/min. (≈100 bar required) And... there's still things not taken into consideration, inaccuracy of the reading on the SPG, the time taken to share gas at 30m, and any other things that might go wrong at depth, but I digress.

To put it simply, I feel that there would be less occurrences of critical OOA/G situations should divers be educated properly in planning their dive (and diving their plan), rather than just simply following the "50 bar limit". Of course, there's still the issue of complacency, like, not checking the SPG, etc. ;)
« Last Edit: 25 Nov 14, 22:20 by snikrs »

alvlim

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Re: What are the causes of Out Of Air (OOA)
« Reply #19 on: 25 Nov 14, 22:45 »
With regards to surfacing with or starting to ascend with 50 bar -

I think it's more than just a good practice to plan ahead and learn "rock bottom gas management" than to simply surface at "50 bar" of gas. In most cases, 50 bar is sufficient to complete a proper ascent with a safety stop, but just simply isn't safe enough, in my opinion.

Let's say a diver has an average Surface Consumption Rate (SCR) of 20L/min, and diving a single 11L tank (80AL), as commonly found in our region. Assuming the diver is at a depth of 30m, and ascending at 9m/min, it would take him about 3 minutes to reach 5m. For the sake of conservativeness (and simplicity in calculation) the ambient pressure is assumed to be a constant 4ATM for the ascent. That journey from 30m to 5m alone will require approximately 20 bar (For the math nut: (20L/min X 4ATM X 3 minutes) / 11L ≈ 22 bar). The safety stop will require approximately another 10 bar (Assuming constant ambient pressure of 2ATM, (20L/min X 2ATM X 3 minutes) / 11L ≈ 11 bar). That's a total of 30 bar from 5m to 30m, without incidence.

In the case of a stressed diver, SCR can easily escalate to 30L/min, and what if he happens to be sharing gas with a buddy? That would mean a total of 60L/min. (≈100 bar required) And... there's still things not taken into consideration, inaccuracy of the reading on the SPG, the time taken to share gas at 30m, and any other things that might go wrong at depth, but I digress.

To put it simply, I feel that there would be less occurrences of critical OOA/G situations should divers be educated properly in planning their dive (and diving their plan), rather than just simply following the "50 bar limit". Of course, there's still the issue of complacency, like, not checking the SPG, etc. ;)

ya totally agree. but if like me not really know how to calculate gas. i would practice going up the boat with min 50 bar in tank after the dive. if have more would be better of cause.

But of cause learning to calculate the gas usage will be a very good thing to do.