I've been having a debate with my dive buddy for an upcoming trip. His S.A.C. Is larger than mine and he is typically down to 500 PSI while I am around 1250 on an aluminum 80. Most of our diving take place between 60 and 100 feet. When we dive air, nitrogen is almost always the limiting factor for me whereas it seems that air remaining is always the limiting factor for him irregardless of the FiO2. We have choice of either 100 cubic foot air tanks or 80 cubic foot nitrox tanks. Any suggestions on which will extend the bottom time for someone who goes through air fairly fast?
Nitrox vs larger tank
- Thread starter Candiru
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pjhansman
Contributor
Nitrox won't give him any more bottom time if air consumption is the limiting factor. It's the same volume of air regardless of what's in it.
Nitrox doesn't extend your bottom time wrt how much you breath. What your SAC rate is is what your SAC rate is - its a volume per-breath thing, not a mixture inside the tank.
If you want more time in the water, bigger tanks is the obvious way. Trying to consciously lower your SAC rate, IMHO, is over rated.
Ergo, you 80s, he dives 100s, with the same gas mix. My wife and I do this all the time - she 100s, me 120s....
If you want more time in the water, bigger tanks is the obvious way. Trying to consciously lower your SAC rate, IMHO, is over rated.
Ergo, you 80s, he dives 100s, with the same gas mix. My wife and I do this all the time - she 100s, me 120s....
The Kraken
He Who Glows in the Dark Waters (ADVISOR)
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Divemaster
Good info above.
Nitrox only extends the amount of time you may remain at a given depth because of the reduction of nitrogen within the mix, it does not change the amount of gas that you breathe per minute.
If you're at 1250 when he needs to come up, perhaps he should look into acquiring a 100 or 119 cf. tank, or two.
Safe dives . . . .
Safer ascents . .
the K
Nitrox only extends the amount of time you may remain at a given depth because of the reduction of nitrogen within the mix, it does not change the amount of gas that you breathe per minute.
If you're at 1250 when he needs to come up, perhaps he should look into acquiring a 100 or 119 cf. tank, or two.
Safe dives . . . .
Safer ascents . .
the K
Or don't worry about it and just dive. 500psi difference isn't much to split hairs about...and its just good insurance if either of you get in trouble at the end of the dive. That's what buddy diving is all about!
Bob DBF
Contributor
Its 750# or 1/4 tank, which would get me looking for a solution. It's good insurance if he has a problem, not so much if you have one. I'd find him a bigger tank and think about Nitrox when NDL limits the dives.
"That's what buddy diving is all about!" I agree!
Bob
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There are more ways than one to skin a cat, however the cat never likes it.
T.C.
Contributor
If you're buying tanks, buy the 100's and have them O2 cleaned.
If you're renting, the place should be able to rent him 100's, and you Nitrox AL80s. It'd be stupid for a shop to make you both dive the same tanks because it's somehow easier on them.
You see, you can have your cake and eat it too.
If you're renting, the place should be able to rent him 100's, and you Nitrox AL80s. It'd be stupid for a shop to make you both dive the same tanks because it's somehow easier on them.
You see, you can have your cake and eat it too.
K
KeithG
Guest
don't go so deep?
Or at least do not spend so much time "as deep as possible". I see way too many divers that shoot to the bottom and then complain about short dives.
I understand if you are in the T&C and cannot finish your dive shallow like in Bonaire. But if you know you (or your buddy) will be limited by tank size, then just stay as shallow as possible. The fish swim up and down. If you wait, they will come. Trust me!
Or at least do not spend so much time "as deep as possible". I see way too many divers that shoot to the bottom and then complain about short dives.
I understand if you are in the T&C and cannot finish your dive shallow like in Bonaire. But if you know you (or your buddy) will be limited by tank size, then just stay as shallow as possible. The fish swim up and down. If you wait, they will come. Trust me!
halocline
Contributor
That's a pretty big difference, either he's an air hog or you're a real sipper. If it's the former, get him to increase his cardio health, and especially work on dive technique to lower his consumption. I've dove with some pretty big dudes that are surprisingly good on air consumption. If it's the latter (you being extra great with air) I suggest you simply enjoy coming up with a lot of air.
My guess is that your buddy could lower his air consumption, unless he's HUGE and you're tiny.
Nitrox won't do anything in this scenario.
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