Abstract: A portable ion mobility spectrometry apparatus (1) for detecting an aerosol and a method for using the apparatus. The apparatus comprises an ion mobility spectrometer (3); a portable power source (5) carried by the apparatus for providing power to the apparatus (1); an inlet (7) for collecting a flow of air to be tested by the spectrometer (3); a heater (4) configured to heat the air to be tested to vapourise an aerosol carried by the air and a controller (2) configured to control the spectrometer (3) to obtain samples from the heated air, wherein the controller is configured to increase a heat output from the heater (4) for a selected time period before obtaining samples from the heated air.