Abstract: A device which measures ethanol levels expelled through a subject's skin to monitor blood alcohol level at regular or random intervals. The device differentiates between a positive reading caused by an external, interferant, source of ethanol and a positive reading caused by consumption of alcohol. The device is attached to the subject by a secure conductive strap which provides an indication that the device remains attached to the subject. The device monitors the skin temperature of the subject prior to performing the alcohol test to provide an indication of a barrier being placed between the device and the subject's skin. The device measures the distance from the subject's skin, thereby preventing the subject from moving the device far enough away to provide an inaccurate indication of the amount of alcohol in the subject's blood and providing another tamper indication if the device is removed.