I just read this question (about emergency lighting) for which nobody highlight the title mention fluorecence. As this lighting's requirements include operability with failure of normal electrical power, having fluorescent strip doubling a ramp of lights make sense. However, the pictures illustrating the answers shows seat-mounted lights.

My question focus on the emergency floor lighting installed on the floor. Do this kind of emergency lighting use fluorecent elements?

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    $\begingroup$ MikeFoxtrot's answer to the original question quotes an FAA document mentioning incandescent lighting (not fluorescent). I imagine that nowadays they are LED strips for reliability and long life. $\endgroup$ – RedGrittyBrick Jul 29 '15 at 16:04
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    $\begingroup$ I think the term the OP wanted is "photoluminescent", specifically "phosphorescent". I answered accordingly. $\endgroup$ – KeithS Jul 29 '15 at 16:05
  • $\begingroup$ @KeithS I don't know the difference between photoluminescent and phosphorescent. I meant the kind of material absorbing radiation and reemitting it as light. $\endgroup$ – Manu H Jul 29 '15 at 16:07
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    $\begingroup$ "photoluminescence" is the term for any material that absorbs light of one wavelength and re-emits a different one. Black-light reactive pigments are an example. "Phosphorescence" is a specific type of photoluminescence where the re-emission of light is delayed significantly, and it's the type of photoluminescence used for any "glow-in-the-dark" material. $\endgroup$ – KeithS Jul 29 '15 at 16:16
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    $\begingroup$ 1) See US Law the technical means is immaterial, the level of illumination is what is regulated. 2) What is normally meant by fluorescent lighting is a glass tubular enclosure containing mercury vapor. An electric current in the gas excites the mercury vapor which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the bulb to fluoresce (i.e. glow). $\endgroup$ – RedGrittyBrick Jul 29 '15 at 16:17

Fluorescent (more specifically phosphorescent as the re-emission of absorbed light happens on a longer time scale) plastics are sometimes used for exit indicators as they're better than nothing when every other system fails, however they have some drawbacks that limit their usefulness, and so they're not relied on as a primary source of emergency illumination in aviation:

  • They're not very bright. Even a battery-backup 5-watt incandescent provides more light, and when passengers are trying to find the exit through a cloud of smoke from an engine fire, bright saves lives.

  • They lose brightness quickly. Here are samples of zinc sulfide on the left and strontium aluminate on the right of each picture. The first picture is immediately after the light source goes out. The second is after just four minutes of darkness:

    enter image description here

    enter image description here

  • They rely on external light sources illuminating them for a minimum time. On night flights (when luminescent exit indicators would be most needed), the cabin lights are often dimmed, reducing the effectiveness of photoluminescent strips. Passenger garments overlapping the strips, such as skirts or waist-tied jackets, will have a similar effect on individual strips.

  • Most pigments react most strongly to UV light which is undesirable for most other purposes. UV light is invisible to us so it's wasted energy, and it yellows plastics (such as cabin trim) which ages airliner cabins more quickly. Light sources that minimize UV are preferable for any purpose except for "charging" photoluminescent strips.

  • They can't be turned off. When cabin lights are dimmed for passenger comfort on a night flight (letting people sleep etc), the photoluminescent strips will make the cabin look like a cheap Halloween party for up to ten minutes after.

In short, there are better options, especially now with white LEDs that are more efficient and less of a fire hazard than incandescent lights. A simple lithium button battery in the same assembly as the light could keep a 50-lumen LED array going more than long enough even in a complete electrical failure, and LEDs bright enough for this purpose are becoming ridiculously cheap thanks to advances in LED lighting for homes and businesses.

  • $\begingroup$ Isn't the OP asking if the floor lighting is made from fluorescent materials or not rather than the advantages/drawbacks. Still, your answer provides some good information. $\endgroup$ – Paul Redmond Jul 29 '15 at 16:09
  • $\begingroup$ I really like to see what this "cheap Halloween party" in mid-flight looks like. Do you have references for the exit indicator you mention? $\endgroup$ – Manu H Jul 29 '15 at 16:11
  • $\begingroup$ Here's an example of a photoluminescent exit sign for commercial construction: encrypted-tbn3.gstatic.com/…. Imagine that on every seat or regular intervals along the floor. $\endgroup$ – KeithS Jul 29 '15 at 16:18
  • $\begingroup$ Here's another example, this time with floor strips: encrypted-tbn0.gstatic.com/… $\endgroup$ – KeithS Jul 29 '15 at 16:19
  • $\begingroup$ @KeithS your picture are quite explicit about the use of such strips. You may consider include them in the answer as such (not use in aviation but elsewhere) $\endgroup$ – Manu H Jul 31 '15 at 7:33

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