A disturbing thread.
Almost a case of Darwin in action.
First rule of using any gas other than air, or potential that could be anything other than air.
CHECK THE GAS - PERSONALLY, do not rely on a third party.
Either standards of tuition have seriously deteriorated or people are not absorbing what they are taught.
The gas should be checked by the diver at the point of sale (dive shop/mixing point).
The gas log should be signed, and the gas mix documented.
The cylinder should be labelled, and the MOD noted.
Ideally the gas should be checked again BEFORE fitting the regulator during assembly of kit.
If there are multiple cylinders of gas in the area, (on the boat), then each cylinder really should be rechecked at the point of fitting the regulator. ESPECIALLY if there are different mixtures on the boat (32%, 36%, air or decompression or custom mixes).
If not, at worst you get an O2 hit, at best you get bent.
I am sure when I did my DM many moons ago, this was very heavily emphasised - and that was for the non-Nitrox qualified DM (, when Nitrox was still considered a technical gas).
More than 20 years of using Nitrox, we ALWAYS check the gas - it is mostly bailout cylinders for me these days as I predominantly use CCR. But we normally have mixed boats of CCR and OC, and the cylinders are personal cylinders, not hired. We still check the cylinder mixes and double check the labelling and MOD's.
There are normally 3 or 4 analysers on the boat.
Scary thread