Self Luminous Exit Signs-How They Work

Tritium Powered Exit Signs

Most exit signs operate on electricity, used to power their LED or incandescent light strips inside. Others are glow in the dark and require the availability of artificial lighting to charge their photoluminescent surfaces. The third type requires no electricity and can be placed in total darkness - the self luminous exit sign!

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It isn't an optical illusion or a magic trick that keeps these self illuminating signs lit. A special hydrogen gas called tritium, which is a naturally glowing green compound, is the magic that makes these signs work so well.

Tritium does not require power from an electrical source nor do they need ambient lighting to be on at all times like glow in the dark exit signs. Depending on how your SL sign is built, it will last between 10 and 20 years! 

How Self Luminous Signs Work

Inside the aluminum and polycarbonate housing, tiny glass tubes are affixed to the backplate of the sign; they are very difficult to dislodge. These glass tubes are internally coated with zinc sulfide phosphor and then filled with tritium gas.

The tritium decays at a snails pace, emitting electrons that cause the phosphor to glow. The big advantage here is you get uninterrupted, consistent lighting that is not affected by outside elements like weather, temperature and moisture saturation.

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Tritium will continue to decay at a defined rate, which makes it very easy for our manufacturers to definitively calculate how much gas needs to be injected in order to provide the brightness for the stated lifespan of the fixture. 

Approved Self Powered Exit Signs

The NFPA 101: Life Safety Code and UL standards set the precedence for the required brightness these signs must meet as well as the contrast between the 'exit' lettering and the sign's background. You must be able to clearly see the lettering from 100 feet away in a pitch dark environment for these signs to pass muster.


Buying a self luminous exit sign may not be for every business. You may have need for many or only a few. Just note that at the end of their life-cycle, tritium powered exit signs must be recycled by a licensed radioactive waste disposal broker, as the gas does contain very low-level beta radiation.

If you're not sure about going self luminous, check out some of our other topics on the website or call us at 800-379-1129 or email our production staff.

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