A filter cartridge for a respiratory mask includes a housing comprised of an inner receptacle having an open end and an outer cover mounted over said open end of said inner receptacle. The outer cover includes, in a covering surface thereof, an air intake aperture in fluid communication with said inner receptacle. The outer cover is pivotally mounted to the inner receptacle and configured for pivotal movement relative thereto between a first configuration in which there is a gap between said open end of said inner receptacle and said outer cover such that a respiratory airway is defined between said intake aperture and said inner receptacle, and a second configuration in which said outer cover substantially seals said open end of said inner receptacle and said respiratory airway is thereby blocked.