The ability to identify a CPAP mask that is comfortable will go a long way towards enhancing your experience with CPAP therapy. In certain cases, it can be a good idea to replace full face CPAP masks . Mouth breathing is one of the primary factors that make people think full face CPAP masks. The size of full face CPAP masks is one of the greatest concerns over switching to full face CPAP masks. Full face CPAP masks are not necessary to all.