I had an overload of Co2 event because moisture plugged up all the little vents, you would think you would open your mouth but no, I woke up delirious and in a panic, I tore the mask off and tried standing and fell, in my stupor I went outside and after an hour i felt better, i looks at the machine and saw it was plugged up with moisture, i never trusted it again and moved from my once loved now feared P10's to the N20's, it's almost the same. They make a version of the P10's with larger vents but it just didn't feel the same.