And hope that the cylinder of air is actually air, not a cylinder that has had EAN in it since being emptied completely.This is exactly why I teach my students to slowly open the cylinder first to make sure you have a light flow and THEN put the analyzer against the valve. They are NEVER to put it against the open orifice and then open the cylinder.
I also teach to calibrate it on a cylinder of air prior to analyzing their Nitrox.