Nitrox Noob Question

[ACR]

I'm sure if I'd done the nitrox course I'd know the answer to this but since I haven't I don't so I'll ask the experts... (that's you guys )

If I have a tank that is 'O2 cleaned' for enriched air clearly I can have it filled with an oxygen enriched mix. If then however I decide to fill it with regular old air does this have the potential to introduce contaminants and require the tank to be 02 cleaned again before going back to EAN?

Another way to ask the question is can I use the same tank(s) for O2 enriched mixes and air?

 

[aquaman_06]

Hello ACR,

Basically what you want to do is make sure the dive center where you are getting your air fill is 02 certified air. This means that their air is equal grade to that used for nitrox blending and wont introduce any contaminants into your 02 cleaned equipment.

Most dive centers offer 02 certified air but I still ask if it's a center where I have never gotten an air fill before.

So the answer is yes to both questions, just make sure your center is using 02 certified regular air.

 

[SelkieDVM]

It depends on the filling station. A lot of places that fill nitrox can provide you with EANx21 (= air) without contamination concerns, so I'd ask wherever you plan to have it filled mostly commonly. Personally, I have separate tanks for air and nitrox.

Cheers,
L.

 

[Zoomer]

Under the PADI course on Enriched Air Nitrox the answer is no. Reason being is IF a fill station uses straight O2 and does a partial fill first than tops it off with straight AIR to get the right blend the tank must be O2 cleaned so that there is not the chance of a potential fire. In other words the tank is exposed to straight O2 first.

 

[Web Monkey]

I'm sure if I'd done the nitrox course I'd know the answer to this but since I haven't I don't so I'll ask the experts... (that's you guys )

If I have a tank that is 'O2 cleaned' for enriched air clearly I can have it filled with an oxygen enriched mix. If then however I decide to fill it with regular old air does this have the potential to introduce contaminants and require the tank to be 02 cleaned again before going back to EAN?

Another way to ask the question is can I use the same tank(s) for O2 enriched mixes and air?

"O2 Clean" and the actual gas mix are completely seperate.

If your shop fills the tank using a method called "Partial Pressure Blending" that involves dumping 100% O2 into the tank, then adding specially filtered air, the tank needs to be O2 clean to reduce (hopefully eliminate) the chance of fire or explosion when adding the Oxygen.

You can however, get air fills with no additional oxygen, using the same air as above, and switch back and forth as desired.

If your shop directly produces Nitrox at a low percentage, usually around 32%, the tank doesn't need to be O2 cleaned and you can also switch back and forth between Nitrox and regular (non hyperfiltered air) air.

However, if your shop does partial pressure blending as above, and you then get a fill with plain, non-hyperfiltered air, they may require you to get the tank O2 cleaned again.

Terry

 

[Jimmer]

Like others have said it depends on the shop. My LDS only pumps O2 clean air, it's the same air I use to top off with when partial pressure blending, so when I fill my tanks with straight air, I'm not contaminating them.

 

[Zoomer]

Also, page 18 of the PADI Enriched Air Diving manual:
Enriched air diving requires a dedicated cylinder exclusively for enriched air use. (nice little pic)
Page 22 from the same book (in bold letters):
Because the tank valve and interior will be in contact with pure oxygen, if partial pressure blending with oxygen will be used, the cylinder must meet oxygen service standards, even if the final enriched air blend will have less than 40% oxygen... The standard scuba cylinder doesn't meet these requirements.
Page 25 of the same book (in bold also):
Standard compressed air from a conventional fill station should never be put into an enriched air cylinder and enriched air should never be put into a conventional scuba cylinder.

Thank you diverdowndh

 

[DivingPrincessE]

To the OP, are you diving nitrox without having taken the class...I didn't know you could do that...

 

[ACR]

So to summarize, it sounds like it depends on three things:

1. The method of blending the enriched mix
2. The air that is used (if it's o2 clean) in the case of air
3. How closely you follow the PADI rules

 

[ACR]

To the OP, are you diving nitrox without having taken the class...I didn't know you could do that...

No I've never dove nitrox and I will be most definitely taking the class before I do. It's more of a future looking question... when I go out and buy tanks will I at some point be able to use those same tanks (assuming they've been cleaned) for both air and EAN?