nitrox to 23.5%?

[xrcjdx]

the answer is probably on the board somewhere, but i didn't find it, and apologize in advance if i should have found it before asking this.

i am buying a 19 to take back 2d home with me (where all manner of everything scuba equipment is off the charts expensive). the tank is "nitrox ready to 23.5%" which is hardly worth even calling nitrox ready.

i thought i would maintain a fill mix of 31%-33% in the tank (depending on the luck of the blender and in any case always within my MOD) to match my frequent back gas. as the tank is only being used as a pony/bail out, i don't see the issue going with just air if it comes to that.

my question is, what's the deal with "nitrox ready to 23.5%"?

 

[oly5050user]

Depends on how mix is created. If 100% o2 is introduced into tank it is not useable unless o2 cleaned. Are you nitrox certified? No such thing nitrox ready 23.5% sounds like you are buying a used tank. Figure on sale cost of tank, hydro test if required, visual, o2 cleaning. Here in NY a hydro test is $35, visual and fill $15, o2 cleaning $50. As you can see after all that you are getting close to the cost of a brand new tank.new tank is o2 clean already.

 

[Caveeagle]

Maybe a typo.. should be 32.5% ??

If you find a shop who banks pre-blended Nitrox, the sticker does not really matter.

 

[xrcjdx]

no, copy and paste from the site: Note: All Luxfer cylinders are nitrox ready up to 23.5%

 

[fmerkel]

I started an extensive thread on what I think is the basis for your question.
NITROX marked tanks MUST be filled to 24% or greater?

Some shops will ONLY put NITROX, defined as a MINIMUM of 23.5%, in a tank with a NITROX sticker on it. This creates a lot of discussion and varied opinions. Read over some of the thread is you want to know more.

 

[WB2GLP]

New Luxfer scuba cylinders manufactured from January 1, 2000, until December 31, 2004, were cleaned for oxygen service at the factory and sealed with an oxygen-compatible cap before being shipped. However, starting on January 1, 2005, Luxfer began providing oxygen-clean scuba cylinders only by special order. Unless specifically ordered "oxygen clean," new Luxfer scuba cylinders will be cleaned for gas mixtures containing only up to 23.5% oxygen. (Of course, it will still be possible to have these cylinders cleaned for use with higher concentrations of oxygen by following the DOT-specified procedures cited above.)

Copy/paste from Luxfer

 

[DevonDiver]

Sounds like marketing BS to me.... if associated with higher prices.

Any tank is acceptable up to 40%. It only needs O2 clean/compatible if it will contain a higher FO2 (41%+).

That could apply if you were using technical decompression gasses, or if getting nitrox (22-40%) fills via partial pressure blending.

The partial pressure blending issue is most likely why some centres will only fill O2 clean/compatible (and marked) cylinders.

As far as the sports diving industry is concerned a cylinder is either O2 cleaned/compatible or it is not.

The 23.5% is probably just to account the a maximal variance in analyser readings when testing air. There has to be some leeway above a strict 21%...but it's not high enough to be a valid nitrox mix that anyone would want (i.e less than 24% which is the leanest nitrox I've ever seen people ask for).

 

[Blue Quaker]

If I remember correctly, CGA standards (and some MIL specs) require any tank used for 23.5% O2 or higher to be O2 clean; below 23.5% O2 = air service...Luxfer is selling, by definition, an "air service" tank....just my 2 cents.

 

[Doby45]

That is only true if you are PP blending. If you are using banked 32% it can go in any cylinder that has current hydro and VIP. Tank "markings" are not required either. But any fill station can make up any rule they want. Such as they only fill with Nitrox stickers on tanks or they only fill if O2 clean regardless of blend method or they only fill pink tanks. Their fill station, their rules..

 

[WB2GLP]

BQ, you are correct. CGA, OSHA, and NFPA specify breathing air as having an O2 content of 19.5 -23.5. (I believe Navy is up to 25%) Beyond that, it's enriched. I would think that the disclaimer is a CYA move.