People remove their mask during sleep because they are not getting enough air.
The CPAP pressure may be reduced if your mask is leaking. Your mask may be too big or too old. We would suggest you resize your mask to be sure you have the best size. If your mask fits you but is six to nine months old, it should be replaced. As the silicone in the mask cushion ages, it deteriorates and becomes too soft to hold a seal. For many masks, you can get a replacement cushion. Go to our Mask Parts section under CPAP Supplies to buy a new cushion.
If the CPAP air is being delivered effectively and without leaks, it may be that the pressure is set too low. Pressure settings may require change due to weight gain or loss and aging. You should speak to your doctor if you think your pressure may need to be adjusted.