A facial mask for the transmission of a gaseous medium to a patient, which incorporates a sealing arrangement which is not damaging to the skin and, concurrently, hermetically seals off the face of the patient. The rim of a facial mask which is adapted to be positioned against the head of the patient has a sealing part which consists of such a material so as to be placeable into a rigid condition through the intermediary of a vacuum or reduced pressure which is present in the sealing part. A removable lid may be provided on the facial mask thereby facilitating that, if need be, the physician is capable of simple and rapid exposure of the patient's face.