Not my words below but interesting like I said no reputable dive shop in the eastern Ontario region will not fill your bottles unless proof of O2 cleaned sticker is on it this could be combined with a VIP sticker.
AN IMPORTANT NOTICE ABOUT NITROX
In recent years, Nitrox has become more and more popular with recreational scuba divers. Unfortunately, this growth, and some recent oxygen related accidents during tank filling, and stage bottle use, mean that nitrox blending, and oxygen clean standards are now drawing the attention of governmental agencies such as OSHA and the manufacturers legal liability council, as well as the CE or European standards agency.((You may not realize it, but most scuba manufacturers sell more equipment in Europe and European commonwealth related countries than they do in the United States)).
The up side of these discussions for recreational scuba is that nearly all of the equipment manufacturers now say their equipment is nitrox compatible for blends up to 40% right out of the box, with no special cleaning, or parts needed. Most small shops do nitrox fills using a method called partial pressure blending. This involves putting pure oxygen into the tank, then topping with air. It is very effective, and efficient, and relatively cost effective to set up. All tanks and valves, however, must be oxygen compatible and oxygen clean, since the first step involves putting the pure oxygen into your tank.
Now back to the OP question yes due to the low vis up here in the St Lawrence river after a rainfall not hard to get confused if there are many divers on a wreck so painting the bottom of the fins with your name or another identifying mark seems to work well, one of the tech instructors has bright florescent pink fins.
