My exit sign / emergency light is buzzing, why? If you push the test button on your emergency light or exit sign and you hear a buzz, this likely indicates that the batteries are dead. This behavior is typically seen with older units that use sealed lead acid batteries and are incandescent. It may make sense to replace the whole unit as newer models are more energy efficient and will, depending on the model, cost nearly the same when you include the labor, shipping, and time. If you have an incandescent exit sign, consider replacing the bulbs with LEDS at the same time as replacing the battery. If you have an emergency light that is buzzing when you test it, replacing the battery will likely fix it.