The best device to kill lice Detects and kills lice No chemicals Easy, safe & reusable. Push the switch to the "on" position. During the entire time the Robi Comb is in operation you will hear a humming sound. Position the Robi Comb so that the flat surface is at a 45 degree angle to the roots of the hair. As you comb the hair, the humming sound will stop momentarily every time a louse is destroyed. Clean the teeth with the small brush provided and the humming noise returns.