Air fills in O2 cleaned tanks...

[mike_s]

If your shop has o2 clean air, you can fill it though with air.

My LDS has an "air" and "nitrox" side to the fill panel. THe Nitrox side is o2 clean for partial pressure filling with much better filtration. If I want an air fill in a Nitrox tank, I get a fill from that side. Think of it as a "21% partial pressure fill".

However not all shops are equipped for this. Some don't filter their air to the required grade, so you can't fill your tanks this way there. (That's why I also have "regular" air tanks also )

 

[waterbearer]

Anybody know the facts on whether or not you can fill a Nitrox approved tank with plain air without invalidating it's Nitrox standing??

That...and is there any danger in putting air into nitrox tanks?

Shop 1: uses continuous flow
Shop 2: uses partial pressure
SHop 3: only has air fills
(actually, I need to double check 3, but for the sake of the question, let's say they only do air fills)

 

[Hoosier]

You can get the air or nitrox from shop 1 and 3 without any concerns. But, you cannot go back to shop 2 for the nitrox fill after filling your tank with non-hyper-filtered air at shop 1 and 3.


If you are only concerning about an air fill, not nitrox, PP doesn't mean anything. You can get the air from any shops.

 

[Whitelightnin]

Here is the scoop on nitrox/air fills. Breathing air is tested to "grade E" standards. Air used to make nitrox is tested to "modified grade E" standards. MOST SHOPS air will pass the "modified grade E" standards if they had it tested to that level. It does cost more to have it tested to that level so shops that don't do nitrox don't have it done. Even shops with the plain jane standard filter system usually have air good enough to pass. They just don't have it tested to that level.

The thought behind not putting plain air in Nitrox tanks is that the air is not clean enough & will contaminate the tanks. Well, if the air is even grade E clean, it would take an awful lot of fills to get enough contamination it the tank to worry about. If you have your tanks O2 cleaned even every couple of years, you will be fine.

Remember, divers have been making nitrox with plain ole ordinary air mixed in plain ole ordinary tanks (NOT O2 cleaned) for the past 20 years or so without a problem. The agencys have now gotten involved & everything is being done to cover their rears. Kinda like wearing suspenders AND a belt to keep your pants up. It will definately get the job done but is it really all necessary?

The shop doing the partial pressure mixing is the one that is taking the risks. If they are willing to work with the tanks, I wouldn't argue with them.

And before someone jumps on me about my opinions, let me state that I understand about O2 & hydrocarbons. I build my own O2 boosters. I am an advanced gas blender & have been doing this a LONG time. It irritated me when someone with "book smarts" tries to tell me how I don't know what I'm doing. If they don't have the experience actually doing it, I'm not interested in hearing about it from them.

James

 

[pescador775]

"lightning" has it right. The above facts and opinions are held widely among divers who own their own compressors and handle oxygen. For example, some "standards" or curricula say that anything above 22.5% requires O2 cleaning. However, home gas mixers and shops will run 40% oxygen through their oil lubed compressors reliably. When handling the straight stuff, hazards increase. However, these primarily involve the valve. New valves with teflon soft parts are usually OK for pure O2. Used valves often contain silicone lube which can be nasty in an O2 environment. They should be cleaned. I don't clean a sparkling new tank and valve before filling with oxygen. The insides of a modern tank are clean enough to reflect light and the valves are usually oxygen safe brass with modern seals and seats. A clean tank can be filled over and over without observing any visible contamination, eg provided that the compressor has an efficient filtration system. "Efficient" is relative but most dive shops pump very clean air and the home mixer is obligated to do so. Thus, the issue is reduced to the fact that shops are up against a pretty hefty set of rules and regs which could expose them to liability and the defense is air testing. For the home mixer, periodic inspections and cleaning to remove invisible residue accumulated over many air fills is good practice.

 

[CompuDude]

You can get the air or nitrox from shop 1 and 3 without any concerns. But, you cannot go back to shop 2 for the nitrox fill after filling your tank with non-hyper-filtered air at shop 1 and 3.

If you are only concerning about an air fill, not nitrox, PP doesn't mean anything. You can get the air from any shops.

So similarly, if I have two tanks that were (at one point) o2 clean, and I have been getting both air and nitrox from one shop and one boat, exclusively, that uses a membrane system (and thus can go back and forth no problem), it sounds like I may need to (a) find out if their "air" is hyper cleaned, modified grade e air, OR (b) get my tanks o2 cleaned again, if I want to take my tanks to a new shop that does PP filling?