A breath analyzer device (1) having an inlet region (2) and a sensor arrangement (3), wherein the inlet region (2) is configured to receive a breath sample from a test subject and direct the sample to the sensor arrangement (3), and the sensor arrangement is configured to provide a signal representative of the concentration of a volatile substance within the sample. The inlet region (2) includes a heater (20, 24) arranged between: a sample inlet port (6) which is open to atmospheric air outside the device (1); and a sample outlet port (11) which is open to the sensor arrangement (3), the heater (20, 24) extending at least part way along a tortuous flow channel (18) which extends between the inlet port (6) and the outlet port (11) for the direction of the sample to the sensor arrangement (3).