A mask may be used in therapeutic gas delivery to one or more external orifices (e.g., the nostrils and/or mouth) of a subject in accordance with an embodiment of the present invention. The mask may include a mask body, a seal portion, a source connector, and an exhaust valve. The mask may be configured to be placed against the face of the subject 12 with a sealed interface therebetween such that a chamber is formed by the mask and the face of the subject that encloses the one or more external orifices of the subject. During use, a breathable substance can be provided into the chamber from a source of the breathable substance through the source connector.
