A self- leak-testing ventilator monitoring module comprising: an internal sensor (160,170,180); internal valves (144,146,148,150); characterized in that it comprises pressure transmission conduits having a proximal end coupled to module input ports and a distal end of the pressure transmission conduits are terminated by a receptacle external to said self-leak-testing ventilator monitoring module, wherein the receptacle is configured for being releasably coupled to at least one of (i) a leak-test-fixture having a gas charging capability from a fixture pressure source, (ii) a self-test plug, and (iii) a connector coupled at one end of flexible tubing of a disposable flow sensor, wherein an opposite end of the flexible tubing includes an airway adaptor configured for being coupled within a breathing circuit, wherein the self-test plug and the disposable flow sensor rely on an existing pressure source for providing a gas charging capability, gas passageways (127,128,152,154,162,164,174) coupled between the internal sensor and the internal valves, and further coupled to said pressure transmission conduits, and a microcontroller configured for controlling said self-leak-testing ventilator monitoring module between (i) an operational, non-test mode and (ii) a test mode, wherein the test mode includes the microcontroller controlling a gas pressure decay test in which the gas passageways are charged with gas to a test-imposed pressure, measuring, using said internal sensor, a change in pressure from the test-imposed pressure by at least a given amount within a predetermined time period sufficient for determining an existence or non-existence of gas leakage (179, 180) from a set of walls (126, 168) that defines respective gas passageways, and responsive to a determination of the existence of gas leakage, the microcontroller is further configured for providing a notification of the determination of the existence of gas leakage. an internal sensor (160,170,180); internal valves (144,146,148,150); characterized in that it comprises pressure transmission conduits having a proximal end coupled to module input ports and a distal end of the pressure transmission conduits are terminated by a receptacle external to said self-leak-testing ventilator monitoring module, wherein the receptacle is configured for being releasably coupled to at least one of (i) a leak-test-fixture having a gas charging capability from a fixture pressure source, (ii) a self-test plug, and (iii) a connector coupled at one end of flexible tubing of a disposable flow sensor, wherein an opposite end of the flexible tubing includes an airway adaptor configured for being coupled within a breathing circuit, wherein the self-test plug and the disposable flow sensor rely on an existing pressure source for providing a gas charging capability, gas passageways (127,128,152,154,162,164,174) coupled between the internal sensor and the internal valves, and further coupled to said pressure transmission conduits, and a microcontroller configured for controlling said self-leak-testing ventilator monitoring module between (i) an operational, non-test mode and (ii) a test mode, wherein the test mode includes the microcontroller controlling a gas pressure decay test in which the gas passageways are charged with gas to a test-imposed pressure, measuring, using said internal sensor, a change in pressure from the test-imposed pressure by at least a given amount within a predetermined time period sufficient for determining an existence or non-existence of gas leakage (179, 180) from a set of walls (126, 168) that defines respective gas passageways, and responsive to a determination of the existence of gas leakage, the microcontroller is further configured for providing a notification of the determination of the existence of gas leakage.