A respiratory mask, comprising: a mask body defining a breathable air zone for a wearer and having two or more inlet ports (603, 604) configured to receive two or more breathing air source components, wherein the two or more inlet ports are in fluid communication with a single fluid chamber defining an opening to allow fluid communication between the two or more inlet ports and the breathable air zone; and a shut-off valve operable between a closed position and an open position, wherein in the closed position the shut-off valve prevents fluid communication between the two or more inlet ports and the breathable air zone, wherein the shut-off valve includes a seal, an actuator and a retainer, the actuator and seal being coupled together and the retainer being positioned between the actuator and seal and securing the actuator to the mask body, wherein the actuator is formed of an outwardly extending flange and a span extending inwardly from the flange, wherein the flange is positioned between a projection of the mask body and the retainer and is attached to the mask body, wherein the flange is sealed against the mask body, so that ingress of unfiltered air from the external environment between the flange and mask body is prevented when the shut-off valve is in an open, closed, or intermediate position, wherein the outer shape of the actuator and flange, when viewed in a plane view in a direction that is perpendicular to a direction of displacement for the span, is round, wherein in the open position of the shut-off valve, the span, when viewed in cross-section in a plane that is parallel with the direction of displacement for the span, bulges outwardly, wherein the shut-off valve is configured and arranged such that when the actuator is depressed, the seal is translated toward an interior wall of the mask body, ultimately blocking the opening when the shut-off valve is in the closed position, and wherein the span, when viewed in cross-section in the plane that is parallel with the direction of displacement for the span, exhibits varying thickness so that the actuator buckles producing an oil canning in response to the force placed onto the actuator when operated from the open position to the closed position, thereby providing a tactile feedback in response to an applied force placed on the actuator. a shut-off valve operable between a closed position and an open position, wherein in the closed position the shut-off valve prevents fluid communication between the two or more inlet ports and the breathable air zone, wherein the shut-off valve includes a seal, an actuator and a retainer, the actuator and seal being coupled together and the retainer being positioned between the actuator and seal and securing the actuator to the mask body, wherein the actuator is formed of an outwardly extending flange and a span extending inwardly from the flange, wherein the flange is positioned between a projection of the mask body and the retainer and is attached to the mask body, wherein the flange is sealed against the mask body, so that ingress of unfiltered air from the external environment between the flange and mask body is prevented when the shut-off valve is in an open, closed, or intermediate position, wherein the outer shape of the actuator and flange, when viewed in a plane view in a direction that is perpendicular to a direction of displacement for the span, is round, wherein in the open position of the shut-off valve, the span, when viewed in cross-section in a plane that is parallel with the direction of displacement for the span, bulges outwardly, wherein the shut-off valve is configured and arranged such that when the actuator is depressed, the seal is translated toward an interior wall of the mask body, ultimately blocking the opening when the shut-off valve is in the closed position, and wherein the span, when viewed in cross-section in the plane that is parallel with the direction of displacement for the span, exhibits varying thickness so that the actuator buckles producing an oil canning in response to the force placed onto the actuator when operated from the open position to the closed position, thereby providing a tactile feedback in response to an applied force placed on the actuator.