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The National Fire Protection Association's 2000 edition
of NFPA - Life Safety Code 101 allows the use of photoluminescent exit signs only if they are in compliance with Underwriters
Laboratories Inc's UL924 Standard for Emergency Lighting and Power Equipment. Underwriters Laboratories in July 2001 updated it's Standard
UL924 by including test requirements for photoluminescent exit signs. The signs must pass a mold stress relief test, a humidity
exposure test, an impact test and a visibility test. Visibilty Testing begins when photoluminescent signs with the correct spelling "EXIT" and the incorrect
spelling "FYIT" are exposed to five foot candles for sixty minutes. They are then kept in full darkness for
90 minutes, while eight observers from four age groups ranging from 18 to 70, test the legibility of the two signs at
a viewing distance of 50 feet. If observers can read the respective signs correctly and quickly after 90 minutes they
are eligible for the UL924 listing. UL924 listed photoluminescent exit signs or signs listed to UL924 are required to
display two important messages on the front. Notice - Legible Viewing Distance 50, 75 or 100 Feet. Caution - Minimum 5 foot candle external unfiltered fluorescent
illumination must be present on the sign face at all times of building occupancy.
Osha's Occupational Safety and health standard, part 1910.37 for exit routes,
requires exit signs to be distinctive in color and illuminated by five foot-candle (54 lux) from a reliable light source.
High performance photoluminescent exit signs fulfill these requirements. Self-Luminous vs Self-illuminating It can be difficult for users to differentiate between a self luminous sign and a photoluminescent sign.
"Self Luminous" is another term for radio-luminescent. These signs are filled with radioactive tritium gas, have
a life expectancy of 10,15 or 20 years and are treated as radio active waste untill their life's end. They can't be
thrown into the trash, but must be returned to the manufacturer for proper recycling. Recycling is very costly per sign usually
in the $150 - $200 range. Photoluminescent Exit Signs are sometimes called self-illuminating and are non-radioactive and
non-toxic. They have a 25 year plus life expectancy rating and can be disposed of normally.
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