I JUST SWITCHED TO A FULL FACE MASK. It seems to fit good, but when I exhale the air does not leave, and it makes it very difficult. Is there a relief valve or something that will let my air exhale out of the mask. Dream Mapper machine thanks
It is a dream Wear mask by phillips.number 113391

Hi
What’s your option of this chart? I know what the gray area is , but what is black on the chart?