Abstract: A method is presented for sensing an environmental parameter, the method comprises the steps of selecting first calibration data for a sensor system, wherein the sensor system is configured to provide sensor data indicating a sensed level of the environmental parameter; providing the first calibration data to the sensor system for use in indicating the environmental parameter; obtaining, from the sensor system, a plurality of items of the sensor data; determining whether a first condition is met by the plurality of items of the sensor data; and, in the event that the first condition is met, sending updated calibration data to the sensor system for use in indicating the environmental parameter, wherein the updated calibration data is based on the first calibration data and the plurality of items of the sensor data.