a flashlight apparatus includes a quantity of tritium within a transparent capsule for emitting light independently of any power source for helping a person locate the apparatus in the absence of substantial external light . the tritium glows in the dark for many years without any external power source . the apparatus also includes the conventional elements of a power source , a primary light source , a power circuit for electrical communication between the power source and the primary light source , a switch , and a housing containing the power source , the primary light source . the light source is preferably a light emitting diode , and may alternatively be an incandescent bulb . the light emitting diode is preferably a high intensity , low power consuming light emitting diode . the transparent capsule includes a vial containing the tritium , which capsule provides a virtually unbreakable enclosure .