Nitrox or Air?

[Charlie99]

ya know, I've never seen anything on a tank that says whether it was o2 cleaned or not. You'd figure that the 'partial blenders' would want to know this before they dumped pure 100% o2 into a tank.

is there any system for this?

is a typical "Nitrox inspection sticker". What it really means is that the cylinder has been cleaned for O2 service.

You can find all you want to know, and a whole lot more on the PSI website

 

[SuPrBuGmAn]

Yeah, the VIP stickers should have an O2 clean addition or you are supposed to have an additional sticker that reads that the tank has been O2 cleaned.

 

[WaterDawg]

Most shops I've seen have a regular VIP sticker, and a different one (usually yellow) that says its been O2 clean. Of course some cylinders (PST) come O2 cleaned...at least thats what their website says.

 

[wedivebc]

The method of blending should make little difference to the end user. Nitrox made by removing nitrogen (DNAx) leaves a higher concentration of oxygen but also a higher concentration of other trace gasses found in air including CO2. Probably not a big deal for 32% mixes but might be an issue for higher % mixes

 

[OneBrightGator]

I'm pretty sure there's no such thing as DNAx.

I'm pretty sure I am right...

I personally prefer not getting partial pressure fills, it takes significantly longer then the other methods, requires dealing with 100% O2 at high pressure (unless you drain your tank, which is a pain too) mixes can vary depending on the filler and is usually more expensive.

 

[Azza]

The DNAx method is good if you get your fills in various places (travelling) and cannot guarantee that you will always be able to attain nitrox or air that is "oxygen friendly", as your tanks do not need to be O2 clean.
Its also faster to get a fill, takes about the same amount of time as a normal air fill, but cannot give fills with more than 40% O2 which is a downside if your shop only has this method and you engage in decompression diving.
Otherwise the ned result is the same...

 

[WaterDawg]

I personally prefer not getting partial pressure fills,

Me too. Pre mix is the way to go. I blend EAN and your looking at a good 15min wait, and thats IF it comes out right the first time. Of course for someone whos been mixing it for a long time its like nothing, but you still have to deal w/ pure O2 and more of a chance to F something up.

But at the end 32% is 32%

 

[Daryl Morse]

The method of blending should make little difference to the end user. Nitrox made by removing nitrogen (DNAx) leaves a higher concentration of oxygen but also a higher concentration of other trace gasses found in air including CO2. Probably not a big deal for 32% mixes but might be an issue for higher % mixes

Depending on the technology (i.e., membrane, pressure swing adsorption, molecular sieve), DNAx will typically enrich gases with molecular weight lighter than N2. Basically, that means argon will be enriched proportionately with O2 (i.e., if you double the O2, you will also double the argon). CO2, CO, and hydrocarbons will be reduced, not enriched.

 

[wedivebc]

Depending on the technology (i.e., membrane, pressure swing adsorption, molecular sieve), DNAx will typically enrich gases with molecular weight lighter than N2. Basically, that means argon will be enriched proportionately with O2 (i.e., if you double the O2, you will also double the argon). CO2, CO, and hydrocarbons will be reduced, not enriched.

Thanks, didn't know that. I don't imagine argon is present in enough quantity to be a concern unless you were approaching pure O2 for rebreather use. The guys at Bikini use one but it only makes 94%

 

[Charlie99]

Thanks, didn't know that. I don't imagine argon is present in enough quantity to be a concern unless you were approaching pure O2 for rebreather use. The guys at Bikini use one but it only makes 94%

Argon is the highest concentration after N2 and O2 --- 1.3 percent of the atmosphere by weight and 0.94 percent by volume. (Actually, Mass. right now, H2O vapor is bigger right now. Uggg. But that gets taken out )

Does anybody have a full gas analysis of a membrane system that they can post?