Photoluminescent Exit Sign Facts
A Guide to Photoluminescent Exit Signs
Unofficially known as "glow in the dark" exit signs, these code-compliant markers work much the same way your glowing toys did as a child - light hits the sign, and it emits a greenish light in complete darkness. However, photolumenescent signs use an industrial grade substrate called strontium oxide, which absorbs more photons and remains lit much longer than the kid versions did.
These environmentally friendly exit signs require no electrical power source or battery, but they do need a little bit of light (fluorescent, metal halide or mercury light is the best) falling on the sign face to remain charged.
How much light are we talking about?
PL signs require at least 5-footcandles of light, or 54 lux. Typical offices measure about 50 lux of average light which, when combined, is more than enough light to keep these glowing signs charged.
Are photoluminescent signs legal?
Photoluminescent exit signs produce more than the Underwriters Laboratories (UL) minimum requirement for emergency egress signage. Most building codes in the U.S. require exit lights to be internally or externally illuminated (PL signs light internally from the glowing material) and must be electrically powered from an outside source (lights are electrical and power the sign externally, therefore meeting UL code). These signs bear the same testing laboratory (UL, ETL, CSA) stamps as electrically powered backup fixtures.
Will photoluminescent exit signs save money?
While they might be more expensive than LED exit signs initially, PL signs don't require a professional to install (saving $100s right off the bat), require very little maintenance, and use no electrical power (which over the course of a few decades really adds up!).
How long do they take to charge?
At the UL 924 minimum required amount of 54 lux, photoluminescent exit signs will take about 60 minutes to fully charge. If ambient light is more than 54 lux, it will actually take less than 60 minutes to reach full brightness.
How long do photoluminescence exit signs glow?
Once it has absorbed enough light to be fully "charged", PL signs will last 15-95 hours in complete darkness before they are fully discharged.
What is the lifespan of a glow in the dark exit sign?
UL's accelerated life-hour tests only go to a maximum of 25 years, so that is the official lifespan. However, strontonium oxide does not decay like radioactive light sources, and could potentially last over 40 years in service!
Is there an expensive disposal process?
Since photoluminescent exit signs are made from earth friendly materials, there are no special handling requirements for disposing photoluminescence exit signs.