Abstract: An apparatus for delivering a breathing gas to a patient includes a display, a storage device programmed to hold different purge hole leak profiles for a variety of mask types, and a selection mechanism for selecting one of the profiles so that accurate values of tidal volume, excess leak and peak flow may be calculated and shown on the display. The displayed excess leak value can be used to correct the fit of the mask.

Abstract: A respirator mask seal and shell are provided according to one embodiment of the invention. The respirator mask seal and shell includes a mask shell having a face opening, a slot for air passage, and at least one attachment portion spaced around the face opening. They also include a movable interface having a hose connector and a contoured opening adapted to fit against the mask shell. The contoured opening is slidable over the slot and is capable of being positioned on the mask shell. The mask seal has a flexible sidewall having distal and proximal ends and includes a rounded outer seal portion located on the distal end of the sidewall, a rounded inner seal portion located between the distal and proximal ends, and a support ring embedded in the sidewall. The inner seal portion is thicker than the outer seal portion and is non-continuous. The support ring includes at least one attachment portion adapted to engage the at least one attachment portion of the mask shell.