Situation.. 4 divers with rented tanks! all which are All unmarked...3 of the divers are nitrox cert.. all are yoke.. the 1 untrained diver grabs the wrong tank.. whos at fault now? Your comparison to anyone with a din should have more knowledge statement is a poor comparison. if thats the case we can compare a Diesel pick up vs a gas pickup truck,, if you own a diesel you Should know that the filler tube on the pump is thicker so that you cant put diesel fuel in the gas trucks gas tank,,, but! you can put gas in the diesel trucks tank! the end result will not be a good 1,, just remember, it isnt a perfect world and theres always room for error. so im pretty sure that those nitrox stickers are worthy for some. These so called band aids arent a user manual,, they are for visual awareness, same as in any industrial shop. the big fire extinguisher sticker on the wall doesnt tell you how to use it, it simply shows you where it is located!