LED 3-step alcohol breathalyser, with new & improved quick response technology. How to use: Press and hold the power button throughout the start-up and testing. First the yellow and red light on the LED will light up to indicate warming-up. Then the green light will light up to indicate ready for testing. Blow into the inhaler for 3-5 seconds. If only green light comes on, then alcohol level is less than 0.02%. If only yellow light comes on, then alcohol level is between 0.02% and 0.05%. If yellow and red lights comes on, then alcohol level is over 0.05%. With a torch and keychain. Includes 2 x AAA batteries.