A flow therapy apparatus, the apparatus comprising: a sensing chamber comprising a flow path for a gases flow; and a controller; the sensing chamber comprising: one or more sensors configured to measure gases properties of the gases flow, the one or more sensors comprising a first ultrasonic transducer at a downstream portion of the flow path and a second ultrasonic transducer at an upstream portion of the flow path; and a heated temperature sensing element configured to measure gases flow rate of the gases flow in the flow path; characterized in that the controller is configured to use output from the heated temperature sensing element and output from the first and second ultrasonic transducers to provide redundancy of flow measurement, the redundancy comprising fast flow measurement at low flows by the first and second ultrasonic transducers and accurate flow measurement at low flows by the heated temperature sensing element; wherein the sensing chamber further comprises a sensing circuit board, wherein a first portion of the sensing circuit board comprising the sensors is configured to be positioned at least partially within the flow path of the sensing chamber; wherein the sensing circuit board comprises at least a second portion of the sensing circuit board configured to be positioned outside the flow path of the sensing chamber; and wherein the sensing chamber comprises a seal dividing the first portion of the sensing circuit board from the second portion of the sensing circuit board. a sensing chamber comprising a flow path for a gases flow; and a controller; the sensing chamber comprising: one or more sensors configured to measure gases properties of the gases flow, the one or more sensors comprising a first ultrasonic transducer at a downstream portion of the flow path and a second ultrasonic transducer at an upstream portion of the flow path; and a heated temperature sensing element configured to measure gases flow rate of the gases flow in the flow path; characterized in that the controller is configured to use output from the heated temperature sensing element and output from the first and second ultrasonic transducers to provide redundancy of flow measurement, the redundancy comprising fast flow measurement at low flows by the first and second ultrasonic transducers and accurate flow measurement at low flows by the heated temperature sensing element; wherein the sensing chamber further comprises a sensing circuit board, wherein a first portion of the sensing circuit board comprising the sensors is configured to be positioned at least partially within the flow path of the sensing chamber; wherein the sensing circuit board comprises at least a second portion of the sensing circuit board configured to be positioned outside the flow path of the sensing chamber; and wherein the sensing chamber comprises a seal dividing the first portion of the sensing circuit board from the second portion of the sensing circuit board. one or more sensors configured to measure gases properties of the gases flow, the one or more sensors comprising a first ultrasonic transducer at a downstream portion of the flow path and a second ultrasonic transducer at an upstream portion of the flow path; and a heated temperature sensing element configured to measure gases flow rate of the gases flow in the flow path; characterized in that the controller is configured to use output from the heated temperature sensing element and output from the first and second ultrasonic transducers to provide redundancy of flow measurement, the redundancy comprising fast flow measurement at low flows by the first and second ultrasonic transducers and accurate flow measurement at low flows by the heated temperature sensing element; wherein the sensing chamber further comprises a sensing circuit board, wherein a first portion of the sensing circuit board comprising the sensors is configured to be positioned at least partially within the flow path of the sensing chamber; wherein the sensing circuit board comprises at least a second portion of the sensing circuit board configured to be positioned outside the flow path of the sensing chamber; and wherein the sensing chamber comprises a seal dividing the first portion of the sensing circuit board from the second portion of the sensing circuit board.