There are several reasons why people might remove their masks while sleeping. We suspect that the most common reasons involve the pressure setting and inadequate air supply. For instance, if the pressure is set too low or the mask is leaking significantly, air supply may be diminished. If the pressure is too high, it may be too difficult to exhale against it or may cause the mask to leak. You may also just need sometime to get adjusted to sleeping with the mask. This is all new to you and the more you use the machine the easier it will become and the quicker your body will get used to sleeping with the mask.