All About Light Sources
Every emergency light and exit sign we carry shares one key feature: they need to light up somehow. All fire and building codes in the United States require egress fixtures to be internally or externally illuminated for at least 90 minutes.
The Science of Illumination
All of our lights and signs generate luminance through electrical energy, heat or sub-atomic reactions:
- Incandescence produces light via a heated element.
- Fluorescence produces light via emitted photon energy.
- Photoluminescence creates light when hit with an electron.
- Radioluminescence produces light due to ionizing radiation bombardment.
- Electroluminescence produces illumination via an electric current going through an element.
Common Lamp Types Found in Battery Backup Lighting
Incandescent - these lamps create an electrical pathway through a heated filament which creates light. Only a fraction of the watts used in these lamps becomes light, and most of it becomes wasted heat. This makes incandescent lamps the most inefficient of all light sources. They are, however, the least expensive bulbs you can get.
Halogen - these lamps generate light in much the same way as incandescent types. The added benefit with halogen lamps is they are much more efficient and last longer than standard incandescents. Inside these bulbs, halogen gas protects the heated filament from "filament evaporation" and allows it to operate at higher temperatures, thus generating more light.
Fluorescent - often in the shape of straight or u-bent tubes, this luminarie produces light via mercury suspended inside the glass envelope. The mercury acts as the "filament" which provides the pathway for an electrical arc. This arc gives off UV light (normally imperceptible to the human eye) which excites the phosphor coating inside the tube. The result is visible light.
Fluorescent is one the most efficient and long-lasting light sources available, second to LED. They generate very little heat, but require a ballast to drive them which can increase manufacturing costs.
Light Emitting Diode (LED) - the longest-lasting electrical lamp available, it uses the principle of electroluminescence to generate light. When voltage is driven into a solid-state diode, light is emitted. Almost no heat is created in this process, making it the most efficient lamp type available. It's also the most expensive.
Photoluminescent - a material that absorbs photons and re-emits them in the form of visible light (naturally green in color). This "glow-in-the-dark" light source does not use any electricity at all, and is 100% safe for the environment. Photoluminescent products like exit signs, hallway tape and stair treads require ambient light to charge (at least five foot-candles of fluorescent, mercury vapor or metal halide lights are the best).
Self Luminous - this product generates illumination in much the same way as fluorescent lamps, using phosphor-coated tubes as the base for visible light. But instead of electrically-generated UV rays, electrons emitted from radioactive tritium gas collides with phosphor molecules, creating fluorescent light.
This radioactive light source requires no electricity or an ambient light to charge. However, tritium gas is considered a hazardous material, which increases the product lead time and disposal costs.