This thought occurred to me this morning. Round here anyway, if you take a tank with no nitrox sticker on it from a dive op (implying air) , it could have anywhere from 21% - 36% nitrox. No one bleeds off a tank's content before refilling. Depending on the roll of the dice you could be breathing almost anything.
btw - the pretty yellow/green band means very little. Alot of tanks with no bands on them are filled with nitrox...
btw - the pretty yellow/green band means very little. Alot of tanks with no bands on them are filled with nitrox...