592978 Disclosed is a surgical mask assembly for administering and scavenging medical gases. The assembly includes an outer shell having a first gas port configured to be coupled to a negative pressure source such that gas is exhausted from the outer shell to the negative pressure source through the first gas port. The outer shell defines a chamber with a rear-facing opening defined by a rim. The rear-facing opening defines an imaginary bounded plane. The assembly includes an inner shell defining a chamber with a rear-facing opening defined by a rim. The rear-facing opening defines an imaginary bounded plane. The inner shell has a second gas port that includes (i) a distal end configured to be coupled to a positive pressure source, and (ii) a proximal end that opens into the chamber of the inner shell such that gas from the positive pressure source is advanced through second gas port and out of the chamber of the inner shell to exit the inner shell. The imaginary bounded plane defined by the rear-facing opening of the inner shell is spaced apart from, and positioned anteriorly relative to, the imaginary bounded plane defined by the rear-facing opening of the outer shell.
