Audio/visual tic rate increases as the sensor tip approaches leak source. Tip light illuminates search area. Flashing LED visual indicator. Detects acetone, alcohol, ammonia, benzene, butane, ethylene oxide, gasoline, halon, hydrogen sulfide, industrial solvents, jet fuel, lacquer thinners, methane, naphtha, natural gas, propane, refrigerants and toluene. 9V battery included. Replacement Sensor sold separately.