Tank for air & nitrox ?

[lachrimae]

Hello everyone & happy Memorial Day. (hats off to our vets)

I went to a LDS today & bought a couple of air cylinders but decided to get Nitrox tanks instead due to their suggestion.

I mentioned that I planned to get my Nitrox cert soon and they suggested that I go ahead and buy the tanks with nitrox ready valves and certification (i.e. large Nitrox Only sticker and small nitrox cylinder validity date sticker). They said that a nitrox ready tank can be used for air as well since you're just using a lower oxygen percentage in a tank that is clean and certified to go up to much higher oxygen percentages.
My main concern which I asked them about was whether or not other local dive shops would be willing to fill a "Nitrox Only" tank with air and they said that, although there may be an occasional exception, most shops would fill it with air. Their word of caution was just to be careful about where I fill up because of the danger of getting lubricants/oils in the tank which could be poisonous later on when I am using Nitrox.

What are your thoughts on using air in a Nitrox tank?

Thanks,

Mark

 

[fppf]

Hummm, does not sound like they told you the whole story there.

First, what makes a tank a Nitrox tank is oxygen cleaning and safe parts. That means that anything that could possible burn in an oxygen rich atmospher is removed. This includes replacing all the seals in the valve and cleaning ALL hydrocarbons out of the tank.

Why, most shops when filling Nitrox use a partial fill methoid. This means the first add 100% pure oxygen to the tank, then top it off with UHP grade "air" to dilute it down to the wanted percent. So there is a time that the tank will have 100% pure oxygen in it.

So, for your question, can you use "Air" in a Nitrox tank.
The quick answer is yes, BUT, and its a important BUT. The air used to fill the tank MUST be UHP grade air. UHP, "Ultra High Purity" is air that has <5 ppm hydrocarbon content. The reason for this is to keep the tank oxygen safe. Most shops use compressors that have oil lubircated crank cases. Some of this oil finds its way into the air system where most of it is filtered out. The UHP grade air will have a second set of filters for hyrdocarbons and other organic compounds.

Now for the almost right part, the UHP grade air comes for a price. In my limited travels so far I have found on avg it have been about $4 for a tank of air. I have also found that it is about $6-$8 for a tank of UHP grade air. And about $10-$14 for a tank of Nitrox. So if you plan on use your Nitrox tanks all the time you could be paying twice as much to dive air.

For my wife and I we bought tanks for each task. But we also do a lot of diving. We have 4 air tanks and 4 Nitrox tanks.

 

[lachrimae]

Thank you, that is very informative...

This LDS charges about $4.50/air fill or $3.50 if you have a 'membership' so UHP sounds unlikely from that perspective although they do fill Nitrox as well so would that mean that they have to be using UHP air? I'll call them to find out... It sounds like the next two tanks that I buy (sometime soon) should probably be air only so that I can have each type of tank. I guess I can use the nitrox tanks with air as long as the filler has UHP air and agrees to put air in my nitrox tanks...

Is there a label on fill systems that shows whether or not the air is UHP or is there a cert I can ask the filler for?

 

[fppf]

That is all information you learn in the Nitrox course. Don't take this the wrong way but a shop should not be selling you Nitrox tanks if you don't have the cert. Nitrox is great if used properlly but nothing is for free and it has its bad sides if your not careful.

The air goes through a second set of filters to make it that clean. Our shop has the normal fill panel and then a line tapped off it going into the second set with another set of fill whips.

There really is not a "standard" fill system with labeling. Most systems are piece mealed together, some are better than others. In any event if you ask any good shop to see there last air sample test results they should be more then happy to show you them. And if there not do you really what to breath that air?

We are a little spoiled, our shop is really top notch. They have there air sampled every 3 months and there compressor is clean enough to eat off it. By there air test results the normal air they use for tank fills is actually clean enough for nitrox fills. But even then they still have the second set of filters and only use that to fill a nitrox tank. They do everything by the book.

 

[COreefer]

For those tanks to be used for nitrox they have to be extremely clean. I would not use regular air in the tanks if you ever intend upon filling them with enriched air. In all actuality you don't need to own nitrox tanks, you can just rent them as needed.

I guess the question that should be asked is..what do you need your own tanks for to begin with? Shore diving, FW diving, or whatever?

I wouldn't use the tanks personally, enriched air is not to be played around with and it seems to me a bit irresponsible that they would sell you a nitrox tank knowing you are not yet nitrox certified. The tank and care is a significant part of nitrox training.


just my .02

 

[fppf]

For the question of why own tanks is very area dependent.

If I was in Maui I would not own a single tank. I found a great dive shop that rented the tank and gave 10 fills for the same cost as just 10 fills are in my area. Also in the NE most dive boats are just charters, they don't do anything but drive the boat. No tanks, no fills, its all bring your own. So that combined with a $30 a week rental fee its worth buying your own tanks around here.

Now besides the money, I personally like to know how that bomb on my back has been cared for. I have had 4 cases when picking up tank rentals that the hydro or visual was out of date.

 

[COreefer]

Yeah I understand why some folks like to own tanks...my question though is for his specific case, why he needs one. If its a situation in which he will never or rarely use nitrox then skip it and buy a regular tank. I guess that's my point.

 

[lachrimae]

You are correct, I am buying tanks because it saves money in the long run for local dives and I will primarily be using air.

The place that I bought the tanks from insists that their air doesn't go through any additional filters when being added to a nitrox filled tank and that, if I use their air, my "nitrox" tanks will be safe for switching back & fourth between air & nitrox.
I'm not saying that I fully believe that because it is not worth risking my life (and my wife's) based upon their "word".

I am about to purchase two more tanks from them so that my wife and I will each have two tanks and the new ones will be air only. I am considering having them convert(?) the other recently acquired tanks back to air only but haven't decided yet.

I plan to take my Nitrox course in just over 2 weeks and suspect that every rule will state that you should NEVER use one tank for both air and 'trox.
Sure, there is the possibility that the air at "Dive World, Austin" is nitrox grade and safe to use but I don't have a way of verifying that beyond a shadow of a doubt.

Thank you again for the info, I've learned a lot thanks to this.

 

[goda]

find a place that fills them with premixed nitrox

place here does taht so you dont even need to have the tank cleaned