JASTEK Breathalyzer Keychain Digital Alcohol Tester Detector Breath Analyzer Audible Alert Portable with LCD Display and Replacement Mouthpiece PersonalHIGH ACCURACY & SENSITIVE . This breath alcohol tester is used to measure concentration of the alcohol in human body. With sensitive semi conductor sensor, this portable breathalyzer can quickly give a result to judge whether you can drive or not. ENERGY SAVING & AUTO OFF FUNCTION. Powered by 2 x AAA batteries( not included, but commonly available), this breathalyzer will automatically shut off to save power after finishing the test for 5 seconds.