Abstract: A respirator mask facepiece thermoformed from a sheet of polymer material includes an opening that is covered by a filter membrane, which may be part of a detachable disposable filter cartridge. The polymer material of the facepiece may be transparent to enable a wearer's lips to be seen. The filter cartridge may include a filter membrane attached to a carrier frame, and may be attached to the facepiece via a set of threads formed on the carrier frame and the facepiece, which draw the cartridge and facepiece together to form a seal therebetween. A latch, catch, or other similar structure may be formed in the facepiece and/or carrier frame to inhibit the cartridge from being inadvertently detached from the facepiece.