Smart Buzzer Breathalyzer: Test Range: 0.00 to 0.19% BAC (or 0.0 to 1.9 g/l). When your test result is equal to or greater than 0.05% BAC (or 0.5 g/l), the "Danger" symbol will appear on the LCD screen with a beep sound. When your test result is between 0.02% BAC (or 0.2 g/l) and 0.05% BAC (or 0.5 g/l), it only displays the "Attention" symbol. " without audible alert. ACCURATE EASY TO USE: Press the power button for 1-2 seconds to start the device, wait 10 seconds for warming up, then blow for 3-5 seconds, the test result will be displayed on the LCD screen, which is designed with an orange backlight, easy to read. Quick response and precise result. SUSTAINABLE ENERGY SAVING: Using 2 "AAA" alkaline batteries (not included), after displaying the result for about 10 seconds, the "OFF" symbol will appear for 2-3 seconds and the breathalyzer will turn off. PORTABLE COMPACT: The breathalyzer with key ring is small and light. It's small and easily slips into a purse or pocket, clipped to a key ring, or placed in a car. 5 mouthpieces, perfect for you and your family to perform blood alcohol testing, providing you and your family with professional precision for safe driving. HOT TIPS: After drinking, it is recommended to wait 20 minutes before testing, because alcohol takes about 20 minutes in the blood from the digestive organs, and residual alcohol in the mouth takes time to dissipate. For a more accurate result, please wait three minutes between each test.