High precision digital breathalyzer: This alcohol tester features a high-precision semiconductor alcohol sensor that quickly provides results to help determine if you are fit to drive. Accurate testing with a range of 0.00% to 1.9% BAC or 0.0 to 1.9 g/L. Ideal for drivers. Easy to use: Simply insert two AAA batteries (not included), turn on the device, and allow 10 seconds for warm-up. Blow steadily into the mouthpiece for 3 to 6 seconds. Results appear on the LCD screen within seconds, remain visible for 10 seconds, and the device automatically powers off. Auto alarm function: If the test result exceeds 0.05% BAC, 0.25 mg/L, or 50 mg/100 mL, the device emits a continuous audible alert to warn the user against driving. For best accuracy, wait at least 20 minutes after consuming alcohol before testing. Lightweight and portable: This compact breathalyzer easily fits in a pocket or bag, making it convenient for use at weddings, parties, celebrations, and other social events to help assess fitness to drive.