Easy to use: Open the electronic breathalyzer. Wait 10 seconds for it to warm up. Then blow evenly for 3 to 5 seconds. Once the breathalyzer test is complete, the Blood Alcohol Concentration (BAC) will be displayed within 3 seconds on the device's bright and easy-to-read LCD screen. Accurate measurement: This certified electronic breathalyzer is equipped with a highly sensitive semiconductor sensor that can quickly and accurately measure blood alcohol concentration. It also has a built-in memory function that saves the last 20 BAC readings for later review. Clear voice prompts: This electronic breathalyzer provides clear voice prompts, including information about breathalyzer readings, power status, and device status. Equipped with three-color LED indicators: During a test with this breathalyzer, the alcohol concentration is indicated by a color: too low (green). Close to the maximum threshold (yellow) and above the maximum threshold (red). Durable and portable: This professional breathalyzer is compact and lightweight and easily fits in your pocket or purse. After the test, it automatically turns off after 10 seconds to save battery. Versatile uses: This personal electronic breathalyzer is ideal for meetings, weddings, banquets, and other social events. It allows you to drive safely after consuming alcohol. It comes with 20 replaceable, washable, and reusable mouthpieces.