An oxygen mask which covers only a patient's nose is attached to the patient by a flexible strap. A clip is attached to the outer surface of the mask to hold the portion of the mask firmly in place relative to the bridge of the patient's nose. An exhaust port is included in the mask. The mask also includes an integral mixing valve for mixing air and gas such as oxygen to achieve a prescribed percentage mixture as may be required for patient therapy. The mixing valve is supported by a support member attached to the mounting strap.