Nitrox question

[ronhend]

When I went through Nitrox class, we were told that the cylinder had to be O2 clean if the nitrox mixing was done in the cylinder.
But, if you were using banked Nitrox, O2 cleaning was not required.

This is what I have been doing, diving reg air on one dive, then have the cylinder filled with banked Nitrox for the next dive.

Now I have been told by another LDS that this is not a smart thing to do.

So, now I'm wondering which is correct. I really like the flexibility of using the same cylinder for both.

Your thought/practice's appreciated.

Ron

 

[RJP]

Your thought/practice's appreciated.

Ron

As long as you're putting "clean" air in it you're fine. In fact, as long as you only ever used banked EANx in it there's really no specific compelling need for an O2 clean tank, since you're never introducing 100% O2 into it. However, you would not be able to get an EANx fill from a shop that did partial-pressure blending.

Where I fill mine we do partial pressure blending, so I O2 clean and always use clean air from the nitrox side of the station.

 

[TSandM]

If the shop is pumping air which is clean enough to mix Nitrox, it should not be a problem.

If you are only getting banked Nitrox, it should not be a problem.

The problem arises when you use air from a source that isn't cleaning to O2 standard, and then have a shop partial pressure blend in your tank. Some shops that bank Nitrox sometimes run out in their banks, and PP blend for the customers. So you have to know for sure that they never do that, if you are going to use "regular" air.

 

[Froid]

My LDS will only fill to Eanx36 if the tank has been used for "regular" air. If you want anything above that or partial pressure blend , it has to oxygen cleaned and tagged.

Another shop in the area will not fill any tank that has been used with "regular" air

 

[mustang_5l]

Don't worry about it. I go back and forth all the time... Just remember to always check your o2 percentages after a fill as you will have residual o2 in the tank.

 

[Thalassamania]

My LDS will only fill to Eanx36 if the tank has been used for "regular" air. If you want anything above that or partial pressure blend , it has to oxygen cleaned and tagged.

Another shop in the area will not fill any tank that has been used with "regular" air

A non-dedicated tank that is clean but not "oxygen clean" should be able to handle anything up to EAN-40 (and that is, trust me, conservative).

 

[Interceptor121]

It depends on how you do the blending. If your tank is filled with membrane or nitrox stik station that mix oxygen at low pressure and you fill the tank with the mixed gas there is no need to clean the tank.
If instead you fill it using a partial pressure blender and therefore you put 100 O2 to start with the tank must be oxygen clean before you fill it with this system and if you happen to mix it at a normal station you need to clean it again as well before putting it through a partial pressure system again
If you are not into trimix and only plan to use nitrox up to 40% I suggest you find a filling station you trust that mixes at low pressure (membrane, stik or others) and always fill it there, this will be cheaper, effective and safe

 

[HowardE]

When I went through Nitrox class, we were told that the cylinder had to be O2 clean if the nitrox mixing was done in the cylinder.

Yes... This is referred to as Partial Pressure Blending. 100% Oxygen is introduced into the cylinder, and then Air is put on top to bring the mix to the right percentage.

But, if you were using banked Nitrox, O2 cleaning was not required.

This is also true. As Thalassamania said

A non-dedicated tank that is clean but not "oxygen clean" should be able to handle anything up to EAN-40 (and that is, trust me, conservative).

This is what I have been doing, diving reg air on one dive, then have the cylinder filled with banked Nitrox for the next dive.

Ok. This is not a problem.

Now I have been told by another LDS that this is not a smart thing to do.

So let me guess... This shop wants to O2 clean your tank, and sell you special air? This is purely BS what they're saying. Period - end of story.

 

[Walter]

This is purely BS what they're saying. Period - end of story.

True, but if it's that shop's policy, you have to either go elsewhere or conform. You can't make them fill the tank. I've run into that same silly policy a few times from otherwise reasonable shops.

 

[HowardE]

True, but if it's that shop's policy, you have to either go elsewhere or conform. You can't make them fill the tank. I've run into that same silly policy a few times from otherwise reasonable shops.

This is true too...

But he said, "I have been told by another LDS that this is not a smart thing to do."

Which is - bull - yes?