I took a trip to Canada a few years ago where we were diving single nitrox tanks every dive and getting close to NDLs. On our second dive, I switched to my twins that I had yet to dive that weekend, which were full of air. I didn't do anything long, and I was buddied up with some of my Nitrox diving buddies, but I had racked up 20 minutes of deco.
Lesson to learn? dive air first, and switch to a richer mix as the weekend/day progresses. Not the other way around.
Lesson to learn? dive air first, and switch to a richer mix as the weekend/day progresses. Not the other way around.