Phosphorescent Emergency

The innovative glow-in-the-dark pigment as a substitute for radioactive self-luminous pigment for watches and clocks is rapidly becoming a useful material for safety systems in commercial aircraft.

"Go!! Go!!" An instructor shouted the order to evacuate the dark cabin. Passengers left their seats and groped for a way to escape. They stooped to avoid the smoke, and saw a line glowing brightly on the floor. It was the phosphorescent evacuation path marking! Passengers followed the glowing line to the emergency exit. In this way, 19 people ranging in age from 19 to 51, including two passengers who had never flown before, were able to escape from the dark cabin.

This is a description of a human observation test conducted by FAA (Federal Aviation Administration) using the CAMI (Civil Aero-Medical Institute) Air Craft Cabin Evacuation Facility to confirm the visibility of phosphorescent floor path evacuation markings in aircraft. Representatives from the aviation authorities of Britain, France and Germany also attended the test.

A hypothetical emergency scenario was used for the test. A nighttime flight of intermediate duration resulted in a lights-out condition of 150 minutes before an emergency landing was made in complete darkness. Inch-wide strips made of conventional ZnS based phosphorescent pigment and strontium aluminate based new pigment were fitted along each side of the aisle. 150 minutes before the test started, the strips were exposed to a 25lux light for 30 minutes.

According to the test results summarized in the FAA report (Feb. 1998, DOT/FAA/AM-98/2)PDF file, strips made of conventional pigment were not visible enough but the strips were easily recognized. The FAA report concluded that the strontium aluminate photo-luminescent materials provide better behavioral cues to guide the individual human observer movements along the aisle toward the exit.

Table: Afterglow luminance of phosphorescent floor proximity markings (mcd/m2)

Type of photo-luminescent material       Time (Min.)

0     30    60       90    120       150

YG-200   13.7       3.8   3.0       2.7   2.5       2.4

Conventional material (ZnS)       14.7 1.6       1.1   0.9       0.8   0.7

Excited with 25lux incandescent lamp for 30 minutes

Measuring conditions; measuring angle - 33 degrees, at a distance of 206cm

Federal regulation 14 CFR 25.812*1 requires that all passenger aircraft must have Floor Proximity Emergency Escape Path Markings. The conventional passenger cabin floor path strips are made with miniature incandescent bulbs or EL panels, which are lit in cases of emergency. The conventional systems sometimes do not work properly because of battery or wiring failures, burned-out light bulbs, or physical disruption caused by vibration, passenger traffic, galley cart strikes, or hull breakage in accidents. In addition to costing money, any repair of these systems would undoubtedly be a cause of delay for some flights.

In the past, Photo-luminescent materials had been tried as a solution to this problem but the available phosphorescent materials did not conform to the brightness and afterglow duration requirements. That is glows ten times brighter and ten times longer than conventional phosphorescent pigment, has solved this problem.

Lufthanza FloorPath

Normal lighting conditions       Dark

Photo: Emergency Floor Path markings in passenger cabin

Similar visibility tests were conducted in Europe also using Airbus A-340-300, with Gumlu proving its superiority again. Lufthansa German Airlines was the first company to adapt its to actual emergency floor path markings. The floor path markings were installed in mid-range passenger aircraft for Lufthansa commercial flights in Europe.

It is said that there currently are about 10,000 passenger aircraft in the world, about one tenth of which have already been equipped with Emergency Floor Proximity markings. Recently, the materials itself has also been improved. New grades can be excited with lower intensity light while emitting a more intense afterglow. It may not be very long before Gluma floor path markings are also installed in long-range passenger aircraft. While it is our sincere hope that such a situation never arises, we are pleased to protect passenger safety.

Passenger aircraft shall have Floor Proximity Emergency Escape Path Marking Systems (FPEEPMS), which will provide visual guidance for emergency evacuation of passenger cabins when all sources of cabin lighting obscured by smoke.

FPEEPMS will enable each passenger to visually identify the emergency escape along the cabin aisle floor after leaving the cabin seat, and to readily identify each exit from the emergency escape path by reference only to marking and visual features not more than four feet above the cabin floor when all sources of illumination more than four feet above the aisle floor are totally obscured and when it is dark.

Transport category aircraft are required by 14 CFR 25.812 to have emergency lighting systems, including floor proximity marking systems. Typical floor proximity marking systems installed on transport category aircraft have been primarily comprised of incandescent luminaries spaced at intervals on the floor, or mounted on the seat assemblies, along the aisle. The requirement for electricity to power these systems has made them vulnerable to a variety of problems, including battery and wiring failures, burned-out light bulbs, and physical disruption cause by vibration, passenger traffic, galley cart strikes, and hull breakage in accidents. Attempts to overcome these problems have led to the proposal that non-electric photo-luminescent materials be used in the construction of floor proximity marking systems. To assess the viability of this proposal, performance demonstrations of systems made with such materials were conducted. It was found that STRONTIUM ALUMINATE photo-luminescent marking systems can be effective in providing the guidance for egress that floor proximity marking systems are intended to achieve; in contrast, ZINC SULFIDE materials were found to be ineffective.

Phosphorescent Evacuation

On March 8, 2000, a subway accident took place in Tokyo. Trains derailed, six people were killed and sixty injured. If this accident had taken place in a tunnel instead of an open area, these numbers would certainly have been much higher. It is easy to imagine the panic caused if the accident victims were unable to determine the correct direction to evacuate the scene. In such situations, it would be very helpful if Glow-in-the-dark signs were installed in tunnels to show passengers the direction and distance to the nearest station.

This phosphorescent Evacuation Route Guiding Sign

directs potential accident victims to the nearest station.

Recently such phosphorescent signs were installed in a tunnel on the Nanboku line subway in Tokyo. The 30 x 60cm signs are made using a special grade phosphorescent pigment, which does not need any exclusive lighting apparatus for excitation. The light leaking from the windows of the passing trains is enough to activate these signs. After the successful field test on this subway line, it is expected that these signs will also be installed in other lines currently under construction.

Glow-in-the-dark signs are helpful not only for subways but also for other underground areas such as shopping malls, underground passages, and basements in the event of a blackout. Therefore the installation of Glow-in-the-dark signs is regulated by fire safety law.

The Fire Fighting Agency's 1988 guidelines regarding "Exit signs and Evacuation route guiding signs" specified that the:

"Installation of emergency signs made of phosphorescent materials is recommended since they emit light even in the dark. Such signs should conform to JIS Z 9100 (Phosphorescent signs) and JIS Z 9115 (Self-luminous signs)"

This JIS standard for phosphorescent signs was recently revised because of the drastic increase in the afterglow intensities obtainable when using phosphorescent pigments, and the new Phosphorescent Safety Signs has replaced the old specifications.

Table: Afterglow luminance of phosphorescent floor proximity markings (mcd/m2)

Type of photo-luminescent material      Time (Min.)

0    30  60      90  120      150

AT20 13.7      3.8 3.0      2.7 2.5      2.4

ZnS     14.7      1.6 1.1      0.9 0.8      0.7

Excited with 25lux incandescent lamp for 30 minutes

Measuring conditions; measuring angle - 33 degrees, at a distance of 206cm

As shown in the above table, the new standard afterglow values are five to six times higher.

European safety signs

Photo; Examples of European safety signs

As far as international standards are concerned, ISO/FDIS 15370 1(Evacuation route guiding signs on passenger ships) regulates that the width of the evacuation pass markings can be reduced down to 25mm from the conventional 75mm (using ZnS based pigment). ISO/CD 17398 2(Safety signs) is currently under discussion for a revision taking this new JIS as a reference.

Phosphorescent material usage in European countries for fire safety signage has the highest utilization in the world. Approximately 100 metric tons per year of Phosphorescent pigment for sheet products is used. Many European sheet manufacturers have already begun to shift their production to high performance.

Emission spectrum of halogen lamp

Do highway tunnels not require phosphorescent signs? Under normal conditions, light is not of concern because of tunnel electrical lighting and headlights of the vehicles using it. However, should an accident or an electrical malfunction occur, tunnel lighting could become a problem. Phosphorescent materials that are effectively excited by headlights would be very helpful for use in highway tunnels. Unfortunately, modern headlights are equipped with halogen lamps. As shown in the above figure, their emission spectrum is not rich in the UV that is the most effective for the excitation. In order to solve this problem, LUMINTEC. were successful in developing a new version which can be excited by halogen lamps. The phosphorescent features of this new grade are shown in the table below.

Table; Comparison of new type with regular type.

After:   1min      5min      10min      20min      30min

Regular      100      100      100      100      100

New type       336      235      214      180      180

Excitation conditions: 600 lux (two 55watt halogen type headlights at 5meters for 30seconds)

The development of this new type has enabled LUMINTEC. to produce phosphorescent signs not only for highway tunnels but also for roads where ambient lighting is not present. This new version will be useful for accident prevention on rural roads or similar places where only headlights are available for excitation of the safety signage.