Switching from Air to Nitrox in the same tank?

Sonic04GT · Apr 16, 2009

I am getting my Nitrox cert once I get back from the desert. However, my buddy is going to come dive with me for a week while we're on leave and he will be diving air and I'd prefer to dive air as well so we have roughly identical NDLs. Then once I head back I'd like to switch my tanks over to Nitrox only. Any problem going this way?

Thanks,
Chris

Jim Lapenta · Apr 16, 2009

This will all be explained in your course but switching from nitrox to air to nitrox can be simple or a pain. If you dive nitrox compatible air you need do nothing. If the air is not nitrox compatible then your tanks must be O2 cleaned if they will be filled using partial pressure blending.

IceBergSlim · Apr 16, 2009

As long as the tanks you use are o2 clean for the maximum percentage you desire you can always fill them with a leaner mix. Make sure the air you are filling them with is o2 clean as well. (Not every fill station provides that level of service)

If you fill the tanks with a "standard air" they will become contaminated and you will have to clean them out when you return to Nitrox blends.

Hope that helps

dwallace · Apr 16, 2009

It all depends on how the Nitrox is made. Some dive shops use Partial Pressure Blending which adds an amount of 100% oxygen and tops up the tank with regular air to obtain the desired blend.
This requires a tank that is Oxygen Clean. Your tank will have to be cleaned of any trace of oil, grease, or other contaminates that would not be a problem using regular air. Other forms of Nitrox (Reverse Osmosis and Constant Blend) usually do not require an Oxygen Clean Tank.

All Nitrox tanks must be marked to show that they are not regular air.

It might be worth your while to have a dedicated tank for Nitrox and one for regular air. Not all dives require Nitrox -shallow dives which have a long NDL and you would run out of gas before you reach a no-decompression limit. Nitrox also has Depth limits depending on the blend. If your planned dive is below the depth limit for Nitrox you could use regular air.

Hope this Helps

paddler3d · Apr 16, 2009

There is a fantastic book about this by Vance Harlow. It is called the 'Oxygen Hacker's Companion' and it is available through Airspeed Press.

Even if you are not going to blend your own, it is still a good read.

There is a section in there that covers your question.

Damselfish · Apr 16, 2009

or if you can't get clean air, no real reason you can't dive Nitrox while your buddy uses air. Just because you have a longer NDL doesn't mean you have to use it. And since you are a new diver the length of your dive may very well be controlled by the amount of air you have. On the other hand, whicle it's good to get the cert, you may decide the dives you are doing aren't worth the price of Nitrox in general.

Graeme Tolton · Apr 16, 2009

What difference does it make if you have a longer NDL than your buddy? It will just have to be his NDL that regulates the dive time. However, if you can get a nitrox fill, you can certainly get an o2 clean air fill from the same place.

Kiwi Sean · Apr 16, 2009

Would it be possible to get a 21% O2 "nitrox" mix for using while diving with your buddy?

elan · Apr 16, 2009

Graeme Tolton:
However, if you can get a nitrox fill, you can certainly get an o2 clean air fill from the same place.

I can be wrong but the above statement only valid for shops using partial pressure method

M_Bipartitus · Apr 16, 2009

O2 clean air is, for all relevant purposes, 21% nitrox.

One could argue that it is preferable to use nitrox even if you are in a situation where air consumption is limiting air time rather than NDL. Nitrox will still result in lower nitrogen accumulation and should reduce DCS risk, even if it wasn't "necessary" to achieve the dive planned. if you use a nitrox mix that results in 25% less dissolved nitrogen in the same dive plan as air, your that much safer. My first scuba instructor summed it up by claiming "better brakes only make safer cars if you drive them the same speed, but many people end up using the better brakes so that they can drive faster and still stop."

Switching from Air to Nitrox in the same tank?

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