Buying air tanks

[mattd]

I've discovered that some shops that bank it below 40 still require it to be o2 clean because they switch over to partial pressure filling when their banks get low and they can't fill my high pressure tanks to capacity on the bank anymore.  It makes sense from a process standpoint because when they are looking at a stack of tanks, how else would they know which they can blend in teh tank and which have to come off the bank.

So, they want you to have an O2 clean valve before putting a nitrox sticker on it.  It makes sense and then you are covered if you are at a site that doesn't have banked air for you.