A valve for a respiratory mask, the valve comprising: a valve housing comprising a valve seat and an inlet; a valve flap at least partially received within the valve housing, wherein the valve flap is sealingly engaged with the valve seat in a closed configuration and is disengaged from the valve seat in a plurality of open configurations, the valve flap comprising a tubular projection extending away from the valve seat along a longitudinal axis, the plurality of open configurations comprising a first open configuration and a second open configuration; a pin slidably received through the valve housing and coupled to the tubular projection, wherein the pin and the valve flap are together movable along the longitudinal axis relative to the valve seat; a valve cage coupled to the valve housing; a central limiter coupled to the valve cage and extending towards the tubular projection along the longitudinal axis; a cap disposed on the valve flap opposite to the valve seat, wherein the cap is engaged with the valve flap and movable along the longitudinal axis; and a biasing member disposed between and engaged with the cap and the valve cage, the biasing member configured to normally bias, via the cap, the valve flap to the closed configuration; wherein, in response to an inlet pressure at the inlet of the valve housing, the valve flap moves linearly, along the longitudinal axis, from the closed configuration to the first open configuration against the biasing of the biasing member, wherein the linear movement of the valve flap from the closed configuration to the first open configuration causes a corresponding linear movement of the cap along the longitudinal axis; and wherein, in the first open configuration of the valve flap, the central limiter engages with the tubular projection to prevent further movement of the tubular projection along the longitudinal axis, such that the valve flap transitions, in response to the inlet pressure, from the first open configuration to the second open configuration in order to remain disengaged from the valve seat, and wherein the valve flap at least partially deforms to transition from the first open configuration to the second open configuration. a valve housing comprising a valve seat and an inlet; a valve flap at least partially received within the valve housing, wherein the valve flap is sealingly engaged with the valve seat in a closed configuration and is disengaged from the valve seat in a plurality of open configurations, the valve flap comprising a tubular projection extending away from the valve seat along a longitudinal axis, the plurality of open configurations comprising a first open configuration and a second open configuration; a pin slidably received through the valve housing and coupled to the tubular projection, wherein the pin and the valve flap are together movable along the longitudinal axis relative to the valve seat; a valve cage coupled to the valve housing; a central limiter coupled to the valve cage and extending towards the tubular projection along the longitudinal axis; a cap disposed on the valve flap opposite to the valve seat, wherein the cap is engaged with the valve flap and movable along the longitudinal axis; and a biasing member disposed between and engaged with the cap and the valve cage, the biasing member configured to normally bias, via the cap, the valve flap to the closed configuration; wherein, in response to an inlet pressure at the inlet of the valve housing, the valve flap moves linearly, along the longitudinal axis, from the closed configuration to the first open configuration against the biasing of the biasing member, wherein the linear movement of the valve flap from the closed configuration to the first open configuration causes a corresponding linear movement of the cap along the longitudinal axis; and wherein, in the first open configuration of the valve flap, the central limiter engages with the tubular projection to prevent further movement of the tubular projection along the longitudinal axis, such that the valve flap transitions, in response to the inlet pressure, from the first open configuration to the second open configuration in order to remain disengaged from the valve seat, and wherein the valve flap at least partially deforms to transition from the first open configuration to the second open configuration.