US Patent 9399105 Mask system

A nasal mask system includes an interface (80) adapted to form an air interface with a patient's nose, and a mouth seal (10) adapted to form a seal (20) with the patient's mouth. The mouth seal (20) is communicated with the interface (80) via a one-way air path (40) that allows exhausted air from the mouth seal to pass into the interface (80) but prevents air from the interface (80) from passing into the mouth seal (10).