A FAN ASSEMBLY

There is provided a fan assembly comprising a motor-driven impeller arranged to generate an airflow, an air outlet arranged to emit the airflow, a plurality of sensors arranged to measure a value for each of a plurality of air quality characteristics, a display and a processor. The processor is configured to receive measured values for each of the plurality of air quality characteristics, identify one of a corresponding set of intervals within which the measured value falls and select an air quality index value associated with the identified interval. The processor is then configured to identify the highest of the selected air quality index values as a current overall air quality index value and to cause the display to display a time series plot of the current air quality index value and a number of preceding air quality index values.