I need some help, please. A few weeks ago I was given a full face mask to try after telling my pulmonologist that it appears my mouth is opening while I sleep, even though I use a chin strap. I've been using a nasal mask. There's no problem with air leakage. However, I gave up with the full face mask because as soon as the pressure increased, the air would start leaking out. It would seem to be okay at the beginning. Before I could fall asleep, though, the pressure increased to the point where it would leak out in a large area. I think the full face mask is the answer to the problem of having my mouth open, but I don't know how to keep it from leaking air. I switched back to the nasal mask for now.