questions about mask

I've had this machine for about 2 years and haven't used it. I'm trying to start now based on some helpful info from some of you. This may sound silly, but I can't remember, for some reason I'm thinking my mouth must stayed closed. I have a full face mask, not sure of the technical term, but it covers my mouth and nose. Does it matter if my mouth hangs open as long as the mask fits snug? and I can't remember what the dial on the machine means, 0 1 2 3 4 5. there is a different button to adjust the pressure so what is the 0-5?

If you have a mask that covers both your nose and mouth, then it's okay if your mouth opens.

The numbers on the dial are for the humidifier control... 0 being no humidity, 5 being max humidity.

What he said--unless your mouth hangs out past the mask, like mine.

thanks so much!!