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When is a photoluminescent sign, the right sign for you?
photo- = Light; radiant energy: photosynthesis.
Recap: Tritium signs are able to fulfill the needs of situations when getting the required electricity is either too costly due to labor and materials or the nature of the environment does not support electricity or wiring (flammable locations/ mental health hospitals/ jails..etc..). We touched on how the signs have a larger up front cost but significantly reduced maintenance fees ongoing. Photoluminescent exit signs share these same capabilities and even cost less but are not ideal for every situation.
As the name suggests "photo" , deals with light, that is the absorption of light from the environment. The energy from light is stored within the pigment coating on the face of the sign. The 'light energy' is then discharged when the balance of ambient light within the room is lesser than the saturation capacity of the pigment, in other words, the room gets darker. The requirements for most building codes is that the sign, regardless of electrical or non-electrical, glow for 90 minutes and maintain a suitable visibility throughout the discharge process. The discharge process and visibility ratings for the sign's design is submitted by the sign manufacturer for tests to be conducted by third party laboratories, such as UL or Entela, who upon successful results apply a listing certifying that the signs meet the code specifications for discharge time. It is imperative that the required code compliant signs used in your operation be are branded with the UL or Entela markings. With an electrical sign, the discharge occurs via a backup battery, with tritium, the sign always glows the same regardless, but with photoluminescent signs, the discharge occurs via the pigments emitting light.
As with the tritium sign, photoluminescent signs do not appear to be as bright as electrical signs when the lights are on. However when you darken the room, you can see that there is a substantial amount of glow radiating from the signs.
Why not use a Photoluminescent sign instead of tritium?
Photoluminescent exit signs can be much less expensive than tritium depending on the model. Like self lit tritium, photoluminescent signs have a wide variance in price. Certain versions range from approximately $60 to several hundred dollars for double face and frame options. The versions that run for $60 are heavy gauge aluminum and are as equally functional as the more expensive versions of the non-electrical signs. The $60 versions do not come with the nice frames, however, they are aesthetically pleasing, do come with mounting holes and are accompanied with a security wrench that locks the signs in place on the wall to prevent dislodging or theft. You can not side mount or top mount the $60 sign, however, the additional brushed frame of $13-20, easily solves that. The sign has no moving parts, and if treated with respect should last for 25 years to a lifetime. The signs do not need to be recycled and since they are non-toxic they very are eco-friendly. The base model sign may be double in price of a basic thermoplastic LED exit sign, but it is half the cost of a 10 year tritium, and is made of durable aluminum making a stronger case for the cost/benefit analysis. The sign has one weakness, it depends on stable lighting in order to stay charged. Stable lighting can mean many things but it must at least mean the following: sign should be charged for minimum 60 minutes to obtain full operation. Minimum 5 foot candles of external unfiltered fluorescent illumination must be present on the sign face at all time during building occupancy.The lighting source can not be direct sunlight which damages the sign. Ambient light can consist of natural light, fluorescent lighting or metal halide, fixtures typically seen in everyday office buildings. The lighting needs to be consistent and the sign must be charged before the room is occupied. The lighting switches that affect the face of the sign also need to be controlled. Your electrician or building code inspector can tell you if these signs are right for your situation.