for my education, why would you shut off oxygen and breathe it down. I was taught if it s a little high breathe it down. But if it’s that high I was always taught dil addition or dil flush. I personally wouldn’t want an in-line shut off on my oxygen. I believe when I did the sidewinder course there was a shutoff on the oxygen and I wasn’t a fan. But ai don’t remember Edd teaching me to shut off the oxygen and breathe it down. And definitely wasn’t taught to in the fathom course. So what would the benefit of breathing it down be other than avoiding having to dil flush or avoiding wasting oxygen.
When you have 32% BO/dil and are at 100ft you have to do a nearly complete dil flush to get the ppO2 to drop. If you're diving 50s and have to do it a few times a dive that's a significant cut into that gas. Sliding it off and breathing it down over 5mins seems so straightforward, and it is - until it's not.