I use a Fisher & Paykel CPAP, I have to wear a full mask that covers my nose and mouth and chin. I have a host of issues mentally, but I have never felt like I was suffocating, while the machine has been on, but I toss and turn and have ripped the hose from my mask before, and then felt breathing discomfort. (has a one way air valve, but with tiny holes in the mask) I have my humidity set at a 1.5 out of 5.