Easy to use: prepare two AA batteries in advance, turn on the power button of the breathalyzer, wait for 15 seconds preheating, then blow evenly for 3-5 seconds, the result will display on the LCD screen for 5 seconds. (Requires 2 AA batteries - not included in delivery) HIGH PRECISION: This breath analyzer uses a high-precision semiconductor alcohol sensor to monitor your blood alcohol level and allow you to drive responsibly; NOTE: For more accurate test results, please stop drinking for 20 minutes. When using the breathalyzer, respect an interval of 2 to 3 minutes between each test. Audible warning and color differentiation: after using the breathalyzer, when the test result is less than 0.08% blood alcohol content, the green light turns on and 3 short beeps sound; When the test result is greater than 0.08% BAC, the red light will light up and 3 long beeps will sound. Measuring range: The alcohol measuring range is between 0.00 and 0.20% blood alcohol content. The blood alcohol test result reaches the maximum value (0.20% BAC) and the value does not increase. Even if the amount of alcohol consumed increases, the test result still indicates a blood alcohol content of 0.20%. Note: For more accurate results, perform 3 tests every 2-3 minutes and calculate the average value.