Oh, I know that! I'm familar with CPAP's and BiPAPs and ventilators, etc. I was a paramedic before I became an engineer. My point was just that, within the context of ventilators, I learned just how little I actually knew about the field of pulmonology and how many things I didn't think would be an issue are actually quite dangerous. What little I picked up would be enough to give me pause about the confident statement made in the comment I responded to about DIY CPAPs.