Circular light rings provide a visual target and notify the user when to start and stop blowing BluFire Sensor Technology provides extremely accurate test results by steadying airflow and requiring a deep lung air sample for each test Tap-proof power button prevents the BACtrack from accidentally turning on Hold power for 5 secs. to display the total number of tests performed BACtrack Alcohol Detector Includes Tester Used for Testing for Alcohol Exhale Through the Breath Chamber, Requires Deep Lung Air Sample for Each Test, Be Sure to Exhale Continuously for 5 Full Seconds, Hold 0.5" from Your Mouth While Exhaling Power Button Prevents Accidental Operation, Compact and Sleek Design, BluFire Sensor Technology Features Easy-to-Read Digital Display, Innovative Inverse LCD Display, On-Screen Instructions Pocket-Size, Patented Dual Flow Breath Chamber Also Includes Carrying Pouch