Q: Why do we need photo luminescent products, when building codes require electrified systems, equipped with battery backup?* Ans: First, and most obviously, because natural disasters, such as hurricanes, thunderstorms, earthquakes or man-made disasters like terrorist bombings and accidental power-line cut by construction crews, often eliminate electrified emergency lighting from the outset. Even in daytime, we can make no assumptions about the reliability of available light, which might be filtered through windows and door openings. Therefore, photo luminescent safety markings - signs, tapes, paints or evacuation plans are important backup to mandatory emergency lighting.
Second, and easily overlooked, is the fact that emergency lighting equipped with back-up batteries requires regular maintenance check of batteries and light bulbs. Since photo luminescent safety products are maintenance-free, the potential for failure attributable to human neglect is eliminated.
The final, and arguably most compelling justification - Code-required emergency lighting could be called "high - location lighting", i.e. "Exit" signs are typically suspended from the ceiling or mounted over doorways. In case of fire, however, smoke can accumulate quickly and being lighter than air, tends to rise. Building occupants are advised to get down on hands and knees and crawl beneath the smoke toward exits. Since high-location signage is now no longer visible, photoluminescent safety markings are installed as low-location lighting. Earthquake prone California, for instance, requires low-location "Exit" path markers in the bottom area of an exit door and continuous low-location path markings along the entire escape route.
Q: Why eight hours duration? *Ans. Emergencies don't come at our convenience. The 1994 Northridge quake struck Los Angeles at 4:17 am. When all the lights failed at one downtown hotel, the escape-route plan on each hotel guest-room door was still visible to darkness-adapted eyes six hours later, long enough to make them visible until daylight, even if the emergency had occurred much earlier.
Q: Okay, but if I don't get out in the first few minutes, I'm probably dead or immobilized by an injury. While I'm waiting to be rescued, six-hour luminance won't be much help, will it? *Ans: In a small building, that may be true, but what about an emergency in a large hotel or office building? It took many occupants of New York City's World Trade Center for six hours to escape from the darkened high-rise towers after the much-publicized terrorist attack in February 1993. Many had to find their way down smoke filled stairwells without any guiding lights. All the code-required high location emergency lights were in place, but the explosion knocked out both main and back-up power supplies. Post attack evaluations showed that photo luminescent markings would have facilitated escape tremendously.