AT68S Alcohol Tester is usingblood alcohol content (BAC) from a breath sample. It can be used in a wide variety of settings including clinical test applications and for personal use. Its uses advanced semiconductor alcohol sensing technology to quickly take a breath sample and provide a blood alcohol content (BAC) estimate. The Lcd graphic display will indicate how inebriated you are, whether it be dangerous (over 0.05% bac), unsafe (approx. 0.02% bac) or safe (under 0.02% bac). Displays "caution" when result is within 0.02% -0.05%, displays "danger" when result equals to or higher than 0.05%