A method for signaling icing within a structure, the structure comprising a circuit (2 - 4), the circuit (2 - 4) comprising an appliance (6, 7, 10, 11), the appliance (6, 7, 10, 11) comprising at least one of: - a damper and/or - a filter (10, 11) and/or - a fluid conveyor (6, 7); the structure comprising a sensor (8, 9, 12, 13) in fluid communication with the appliance (6, 7, 10, 11); the method comprising the steps of: recording a first signal indicative of a physical quantity associated with the appliance (6, 7, 10, 11) using the sensor (8, 9, 12, 13); after recording the first signal, recording a second signal indicative of a physical quantity associated with the appliance (6, 7, 10, 11) using the sensor (8, 9, 12, 13); processing the first signal to produce a first measure and processing the second signal to produce a second measure; producing a differential measure as a function of the second measure and as a function of the first measure; comparing the differential measure to an icing threshold; and producing a signal indicative of icing within the structure if the differential measure exceeds the icing threshold; wherein the circuit (2 - 4) defines a flow direction; wherein the appliance (6, 7, 10, 11) comprises a downstream side pointing in the flow direction and an upstream side arranged opposite the downstream side; wherein the appliance (6, 7, 10, 11) comprises a downstream port arranged on the downstream side and an upstream port arranged on the upstream side; characterised in that the sensor (8, 9, 12, 13) is in fluid communication with the appliance (6, 7, 10, 11) via the downstream port and via the upstream port; and wherein the sensor (8, 9, 12, 13) is a differential pressure sensor, the differential pressure sensor (8, 9, 12, 13) being arranged to produce a signal indicative of a pressure difference between the downstream port and the upstream port. the circuit (2 - 4) comprising an appliance (6, 7, 10, 11), the appliance (6, 7, 10, 11) comprising at least one of: - a damper and/or - a filter (10, 11) and/or - a fluid conveyor (6, 7); - a damper and/or - a filter (10, 11) and/or - a fluid conveyor (6, 7); the structure comprising a sensor (8, 9, 12, 13) in fluid communication with the appliance (6, 7, 10, 11); the method comprising the steps of: recording a first signal indicative of a physical quantity associated with the appliance (6, 7, 10, 11) using the sensor (8, 9, 12, 13); after recording the first signal, recording a second signal indicative of a physical quantity associated with the appliance (6, 7, 10, 11) using the sensor (8, 9, 12, 13); processing the first signal to produce a first measure and processing the second signal to produce a second measure; producing a differential measure as a function of the second measure and as a function of the first measure; comparing the differential measure to an icing threshold; and producing a signal indicative of icing within the structure if the differential measure exceeds the icing threshold; wherein the circuit (2 - 4) defines a flow direction; wherein the appliance (6, 7, 10, 11) comprises a downstream side pointing in the flow direction and an upstream side arranged opposite the downstream side; wherein the appliance (6, 7, 10, 11) comprises a downstream port arranged on the downstream side and an upstream port arranged on the upstream side; characterised in that the sensor (8, 9, 12, 13) is in fluid communication with the appliance (6, 7, 10, 11) via the downstream port and via the upstream port; and wherein the sensor (8, 9, 12, 13) is a differential pressure sensor, the differential pressure sensor (8, 9, 12, 13) being arranged to produce a signal indicative of a pressure difference between the downstream port and the upstream port. recording a first signal indicative of a physical quantity associated with the appliance (6, 7, 10, 11) using the sensor (8, 9, 12, 13); after recording the first signal, recording a second signal indicative of a physical quantity associated with the appliance (6, 7, 10, 11) using the sensor (8, 9, 12, 13); processing the first signal to produce a first measure and processing the second signal to produce a second measure; producing a differential measure as a function of the second measure and as a function of the first measure; comparing the differential measure to an icing threshold; and producing a signal indicative of icing within the structure if the differential measure exceeds the icing threshold; wherein the circuit (2 - 4) defines a flow direction; wherein the appliance (6, 7, 10, 11) comprises a downstream side pointing in the flow direction and an upstream side arranged opposite the downstream side; wherein the appliance (6, 7, 10, 11) comprises a downstream port arranged on the downstream side and an upstream port arranged on the upstream side; characterised in that the sensor (8, 9, 12, 13) is in fluid communication with the appliance (6, 7, 10, 11) via the downstream port and via the upstream port; and wherein the sensor (8, 9, 12, 13) is a differential pressure sensor, the differential pressure sensor (8, 9, 12, 13) being arranged to produce a signal indicative of a pressure difference between the downstream port and the upstream port.