Dont risk your safety or your driving licence by guessing whether youre fit to drive a few drinks can take up to 14 hours to leave your system so you can even be over the limit the morning after the best weve tested this breathalyser uses an easy traffic light system simply breathe into the device for 3 4 seconds and the display will indicate green for safety amber for caution or red for danger when youre close to or over the limit it also displays your blood alcohol content bac