I'm in Dominica now, diving with Cabrits Dive Centre. They fill their own tanks and have their air tested quarterly. I tested seven 12.7 L aluminum cylinders today. All seven cylinders did not even bounce off 0 with my Analox CO analyzer. They don't fill Nitrox but I checked anyway. All seven cylinders were at 21%.
I'll post more results tomorrow.
I'll post more results tomorrow.