A mouth pipe and porous filter unit for operation of a device, e.g. a pneumatically actuated device, comprises a mouth pipe in communication with an air tube for delivering blown air to the device. The mouth pipe comprises a one-piece transparent thermoplastic extrusion member and has an integral projection for grasping the mouth pipe. The porous filter has a pore size ranging from 90 microns to 130 microns for preventing saliva and/or blood of a patient from flowing into the air tube and surrounding environment. The mouth pipe comprises a first diameter section, a transition member, and an enlarged second diameter section which form a continuous airway therein and the porous filter is wedged within the enlarged second diameter section of the mouth pipe. The material of the mouth pipe may be polyvinyl chloride, and the material of the filter may be polystyrene.