High Accuracy and Fast Sensor: The alcohol tester comes with professional airway design and high accuracy semiconductor sensor. Accurately display blood alcohol content quickly. You can then decide to drive after drinking. Easy to use: Just insert the three 1.5V AAA batteries, then connect a mouthpiece, press the start button for the countdown initialization, warm up for 10 seconds, blow into the inhale for 5-10 seconds, the blue backlight LCD will show the test result directly. After the result is displayed, you can press the power button to change unit.battery not included Auto alarm function and power saving mode: There are 3 measurement units to choose from, % BAC, BAC , mg/L, when the test is performed, if the measurement result exceeds 0.5 BAC, the breathalyzer will warn with an audible alarm. The breathalyzer automatically shuts off to save power when no operation. Compact and portable design: The breath alcohol analyzer in mini size, small enough to fit in your car, purse, backpack or briefcase. It's convenient to have a portable bag, it can perfectly hold the breathalyzer and mouthpieces when you are anywhere.