US Patent 10905903 Respirator having optically active exhalation valve

Various embodiments of a respirator (10) that includes a harness (13, 16), a mask body (12), and an exhalation valve (14) are disclosed. The exhalation valve (14) can include a valve seat (20) and a flexible flap (22) that is in engagement with the valve seat. The flexible flap can have one or more materials that can cause the flap to flash (26) when moving from a closed position to an open position or vice versa. The flashing valve can make it easier for a user to ascertain whether the valve is operating properly.