..@Dumpsterdiver: That's not what is being taught in training. Everyone makes mistakes, and a mistake with filling or analyzing an EANx tank can easily get you seriously injured or killed. It's not smart to trust anyone on this, especially people you don't know... Would you take a pil from some random stranger you meet on the street just because he says it doesn't do any harm?
I don't really care what is being taught in a class. My point was that you were willing to trust your life to strangers underwater who seemed to have very little regard for your safety, yet you don't trust them (or the tank mixer) to give you a proper fill.
If that what is taught in a class, I think you should re-examine it. Which is more dangerous (when you are carrying zero redundant gear) to trust someone to stick with you through all the complexities of a challenging deep dive in bad vis or to mix a freaking tank?
Also as someone else mentioned, you dove an "air" tank from the guys who had nitrox tanks, yet you never checked the contents of the "air" tank. I know, i know, they teach you in the class that this is prefectly fine because ????? people never make mistakes and mix up a nitrox and an air tank right?
I personally will trust another person to check the mix of a tank that i use, I do it commonly actually, but as mentioned previously..I KNOW THEM.. We trust our lives to other people all the time..ever fly in a commercial aircraft or ride in abus or a taxi?
I think it is somewhat silly to refuse a tank because you didn't check it, yet you blindly buddy up with people you have no reason to trust, yet you dive with zero redundancy.