Have you ever thought to an exit sign, or to all similar facilities in streets, public buldings, airplanes, boats and so on that say something to us (e.g. where the emergency exit is) and consume energy?
Most exit signs around the world are in pictogram form, with or without text supplement. There has been a shift towards the adoption of such exit signs in the recent decade.
Regarding to Environment Care, “Self Luminous Exit Signs” do not require an external power source or battery backup. They use a mechanism similar to fluorescent lighting, but powered by tritium instead of an electrical current, and are available in models that are rated to last up to 20 years. The half-life of tritium is 12.5 years. The Tritium is hermetically sealed in a glass tube, and poses little risk of radiation exposure. Proper disposal of the radioactive material is required, and may be expensive.
A small minority of nations adhered to the exit signs that show the word “EXIT”, “EXIT SIGNS” (or similar in another language). Its purpose is guiding people to the closest exit in case of fire or other emergency. The English word “exit” comes directly from the Latin word meaning “to go out.” Most fire codes require exit signs to be permanently lit.
Since visibility may be reduced in a fire, due to smoke or failure of electric lighting, the sign is often permanently illuminated, usually by one of electric light, with a local rechargeable power source; radioluminescence, (`traser`), self-luminous, where a phosphor coating inside a glass tube glows due to the beta decay of radioactive tritium in the tube; hosphorescence (`glow in the dark`), where light is absorbed from the surroundings and slowly re-emitted; electric light, with the building`s emergency lighting circuits providing back-up power from a UPS and/or a generator in case normal power is lost.