Abstract: The invention discloses a respiratory protective device having “Twist and Click” locking mechanism on the threaded circular joint on an inner yoke fitting part of half mask face-piece and replaceable non symmetrical filter, thereby allowing an non symmetrical filter having a non symmetrical geometry to be positioned perfectly, correctly and easily on inner yoke part of mask face-piece with reduced slippage and quick assembly.

Abstract: A butterfly type exhalation valve comprises a bottom valve body of cylindrical/oval shape with a boss at one end provided with smooth surface at other end to form a valve seat for mounting a butterfly type diaphragm. A support provided at center of internal diameter with two or more sector openings forming exhalation slots. A solid pin forming a fulcrum for the diaphragm provided in the center of the support. One or more locking grooves provided to the outer vertical surface of bottom valve body. A cap having a rigid top is provided with a hollow pin, at center, in the inner side to engage the solid pin of the valve body when mounted over the bottom valve body after locating the diaphragm to the solid pin. One more slots on the side surface just below the top of the cap provide for passage to exhalation air.