Air use and Dive Planning

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esbuff

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Location
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Being a new diver I have little experience with the actual planning of a dive. That being said how do you plan your dives in reference to air use, turn pressure, and air remaining. I realize you need to take depth, buoyancy, equipment, comfort level, exertion and other factors into account, but where do you begin and what do suggest when planning your dives?
 
You turn on 50bar or 500 psi. This information should have been (or was) covered in detail in your training.
 
If you begin your dive with 2500-3000psi why would you wait until 500psi to turn. I would think you would want 500psi at the end of the dive?
 
You turn on 50bar or 500 psi. This information should have been (or was) covered in detail in your training.

If you begin your dive with 2500-3000psi why would you wait until 500psi to turn. I would think you would want 500psi at the end of the dive?

I think he's got you there... :)

NWGratefulDiver has an excellent article on gas planning.
 
I'm also new to diving and that is covered in your PADI training. 800 psi is the suggestions because you also have to take in consideration your 3 minute safety stop. This is also something you would discuss with your diving buddy.
 
If you begin your dive with 2500-3000psi why would you wait until 500psi to turn. I would think you would want 500psi at the end of the dive?

You are farther along than you thought :wink:

This is what Cave Diver was referring to LINK < NWGratefulDiver.com >
 
Being a new diver I have little experience with the actual planning of a dive. That being said how do you plan your dives in reference to air use, turn pressure, and air remaining. I realize you need to take depth, buoyancy, equipment, comfort level, exertion and other factors into account, but where do you begin and what do suggest when planning your dives?

Great question ... and you are absolutely correct that your air is a resource that should be considered as part of your dive plan.

Think about diving as though you're about to take a drive across a desert ... where the only gas you can rely on is what you're going to be taking with you. What information do you need to know?

- how many "miles" will I be going?
- how many "miles per gallon" does my car get?
- how will conditions affect my "miles per gallon"?
- how much gas do I have in my tank?

Diving's just like that. So the answer to where do you begin is that you first need to figure out your "miles per gallon". This is what's commonly known as your "Surface Air Consumption" ... or SAC rate. The key thing to understand about it is that ... just like the miles per gallon in your car ... it's not a number, it's a range that's determined by a number of variables such as the diving environment and your diving habits.

Once you determine your SAC rate, you can use it to calculate how much gas is appropriate for your dive plan ... basically answering the question, "do I have enough air for the dive I want to do?"

The other significant thing you want to determine is how much gas you need to reserve for emergencies ... keeping in mind that you also want to reserve enough to share with your buddy if for any reason they should encounter a problem.

There's an article on my website called Understanding Gas Management that explains in detail how this all works. You may find it helpful ...

... Bob (Grateful Diver)
 
First, commence your ascent with no less than 700 psi ( a bit more if you are deep, 600 is ok if you are shallow). Be aware of how much air you have left by checking your gauges regularly. You will find that consumption seems a little faster at first, and a little slower in the bottom 1/3, but the differences are not great. Always head back to you point of origin if you are at 1/2 of a full tank. I like dives where we don't travel real far- I like to look at things, particularly interesting fish and other animal behaviors, so often our dive will not take us very far from our point of descent. In such cases, we still monitor air closely, but without concern for the "trip back." The reason people get into trouble with air supply is most often failure to look at their gauges regularly. Look at them regularly. As you log more dives and bottom time you will find that air supply is usually less limiting than NDL's so you can plan accordingly. For a few tips ( with a bit of humor and sarcasm) on reducing air consumption, there is a discussion in "The Scuba Snobs Guide to Diving Etiquette" in chapter 6.
DivemasterDennis
 
I see some comments that would confuse the hell out of me if i was the one asking this question. Sure you can "turn" with 500 PSI left providing you havent left the shadow of the boat.

Ideally you should be back ON THE BOAT with 500 PSI. A lot depends on what the dive involves. I would suggest taking some advice from the few on this forum that really do know what they are talking about and I am not one of them.
 
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