yes but Ive just done a pre dive tests that verified all those things work. so the only thing it could be testing is scrubber breakthrough...and i strongly suspect anything less than a reasonably big bypas wouldnt show up pre breathing sat on a bench....but if someone proves me wrong Im happy to change my opinion. I dont recall ever hearing about anyone finding a problem with scrubber during pre breathe and I do recall people whos unit passed pre breaths then they had breakthrough on descent....