High precision digital breathing analyser: This alcohol tester has a high-precision semiconductor alcohol sensor. It can quickly provide a result to judge whether you can drive or not. Test winner with 99.1 percent , range of 0.00 percent - 1.9 percent BAC or 0.0 - 1.9 g or l. Ideal for drivers. Easy to use: simply insert 2 AAA batteries (batteries are not included), turn on your alcohol tester. Wait 10 seconds to warm it up and then blow for 3-6 seconds. The result will be displayed later on the LCD screen. The results are displayed for 10 seconds and then automatically switched off. Auto Alarm FunctionTest result is over 0.05 percent BAC or 0.50 BAC or 0.25mg or L or 50mg or 100ml, alcohol tester gives a continuous beep of itself and to remind drivers not to drive. (Wait 20 minutes after drinking to perform the test, the result will be more accurate) Lightweight and portable: alcohol tester can be carried anytime and anywhere in your pocket or wallet. It is very suitable for weddings, parties, celebrations and other social events to help you judge whether it is suitable for driving.