Exit signs is a device in a public facility (such as a building, aircraft or boat) that displays where the emergency exit is, guiding people to the closest exit in case of fire or other emergency. Most relevant codes (fire, building, health or safety) require exit signs to be permanently lit and display certain pattern they completely specify. Exit signs are designed to be absolutely unmistakable and universally understandable to anyone who sees them.
Most Self Luminous 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. A small minority of nations adhered to the exit signs that show the word "EXIT" (or similar in another language). The English word "exit" comes directly from the Latin word meaning "(he or she) goes out."
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:
* Radioluminescence, ("traser"), self-luminous, where a phosphor coating inside a glass tube glows due to the beta decay of radioactive tritium in the tube. Radioluminescence Photoluminescent Exit Signs are prohibited in US Department of Defense installations.
* Phosphorescence ('glow in the dark'), Photoluminescent, where light is absorbed from the surroundings and slowly re-emitted.
* Electric light, with a local rechargeable power source.
* 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.
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