| http://www.w3.org/ns/prov#value | - The valve 160 includes a cylindrical member or spool 162 adapted to fit within the changer 128 and having a seating surface 164 formed of a layer of elastomeric or other suitable sealing material for sealingly engaging the surface 166 containing apertures 142, as illustrated in FIG. 11, for preventing breathing gas from leaving the face mask 22.
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