Tassi Devil Diver
Contributor
Since I have been diving rebreather any dive over 30m (100ft) I use helium in my diluent and generally keep my END to around 25m for deeper dives, not only because using He in a rebreather is more economical, but I don't want to be in any situation where I could confuse the onset of a CO2 hit with narcosis or have narcosis impair my ability to react to issue on the rebrather, plus I don't miss those feelings of impending doom I got from time to time when diving deeper on air. Thank god those days are long behind me.