Nitrox diving and your computer settings

[scubapeople59]

Hi, Just wondering why you would not want to dive with your computer set on nitrox with a 21% mixture, while diving with a regular air mixture?
Thanks

 

[fppf]

By setting the computer to "21% Nitrox" it will turn on the oxygen exposure tracking calculations. Other than that there is no change to the decompression calculations.

Its actually good to set the computer to 21% if your doing air dives and then nitrox dives later.

 

[HowardE]

Hi, Just wondering why you would not want to dive with your computer set on nitrox with a 21% mixture, while diving with a regular air mixture?
Thanks

Why wouldn't you? Does your nitrox computer offer 21% as an option?

Most recreational computers say, "Air, 22, 23, 24... etc."

My Shearwater doesn't say "air" but it only offers a % of o2. If I'm using Air... I set it to 21%

 

[Bazooka Joe]

All 3 of my Oceanics and my Aeris Manta have Air and 21....I was ready the manual on the Oceanic today and the reason they give the option of both 21 and Air is, if you have a dive on Notrix say 32% then your next dive is Air...the computer will not alloow you to set it to Air. It will allow you to set it to 21% for the O2 tracking.

 

[Damselfish]

no real reason not to. Actually at least in the case of most Suunto computers, if you dive Nitrox at all it's best to put the computer in Nitrox mode and leave it there, and set it to 21% when diving air. Reason being, once you have started a dive series you cannot switch modes until the computer clears so you will be stuck in air mode. And if you might be diving Nitrox you really want it tracking oxygen exposure on all dives anyway, even though that is not usually a problem.

 

[scubapeople59]

I am using a Suunto Cobra that will do the same thing. If I have my first dive of say 32% and my next dive is air, the computer will only allow me to set it at 21% in the nitrox setting. I started the thread because I recently read an article about setting your computer to 21% in the nitrox mode and why you should not do this and I can not find the article. It is driving me nuts. It was in either Sport Diver or Scuba or Dive Training or Under Current. Perhaps someone read the same aritcle.

 

[deepstops]

Actually at least in the case of most Suunto computers, if you dive Nitrox at all it's best to put the computer in Nitrox mode and leave it there, and set it to 21% when diving air. Reason being, once you have started a dive series you cannot switch modes until the computer clears so you will be stuck in air mode.

Exactly. I was diving in Cozumel with a friend and we found this out the hard way. If you're diving nitrox at all, you must use 21% nitrox instead of air on a Suunto.

 

[h90]

mine only has "Nitrox" and for Air you are supposed to set it to 21 %. Which is logic.

 

[Crowley]

I leave mine (Suunto Vyper) permanently in Nitrox mode - it defaults to 21% and obviously can be set as required.

One of my employers insists that all instructors and dive guides dive on nitrox (yay!) but I leave my computer set at 21% - so I don't break NDLs for the air divers. Of course, that is subject to depth limitations but since they pump out a standard 32% mix (MOD for 1.4 ata ppO2 = 33m) and I rarely dive beyond 30m, it's all kind of academic. If I do, I make sure I have a gas appropriate to what I'm doing.

So there's no real reason to NOT dive with ith your computer set at Nitrox 21% - it will make the extra O2 exposure calculations but within recreational limits on air, this is mostly irrelevant. The main reason I leave my computer set this way is because it saves pressing buttons!

Hope that helps.

C.

 

[ivobj]

I see no reason not to do it...