This breathalyzer is compact in appearance, very portable and can be tucked inside your purse, with a clock display, simple design with a dust cover,so more clean,red LCD digital display, with a buzzer sound alert Only detects alcohol content, no other extra functions interfere, so more accurateNeed to install 2 AAA batteries (not included), very low power consumption, longer standby time, with automatic shutdown function. Easy to use turn on the power button of the alcohol tester, wait 10 seconds for the warm-up time, then blow evenly for 3-6 seconds, the result will be displayed on the LCD screen within 5 seconds. If the alcohol concentration reaches 0.020%-0.050% BAC 0.100mg/L-0.250mg/L, it will show the warning, more than 0.050% BAC, 0.250mg/L, it will show the danger and sound the buzzer, for the accurate data, please repeat the test several times, the interval is 2 minutes, there will be a small change of value, it is normal. After drinking alcohol, wait 20 minutes before testing because alcohol has not yet entered the bloodstream within 20 minutes, affecting the accurate value. If you have any questions, please contact us through Amazon and you will get a reply immediately