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Photoluminescence Shines Through

• Jun 01, 2004

TWO high-rise building evacuations last year focused building owners and city officials nationwide on the issues of adequate signage and evacuation systems. Thousands of workers and diplomats successfully found their way out of the United Nations headquarters in Manhattan during the massive Aug. 14 electrical blackout. On Oct. 17, six office workers died of smoke inhalation in a stairwell while trying to escape a fire on the 12th floor of Cook County's 35-story administration building in downtown Chicago.

Certainly we can't equate the two emergencies. In the following days, the Chicago fire provoked more questions about why a general evacuation even occurred and why the county building lacked sprinklers, pressurized stairwells, and other safety features than about what type of signage was present to aid workers' escape. Part of the UN success story was a photoluminescent egress marking system--one that shines brightly without electricity. The system's suppliers say it helped evacuees quickly and safely find their way out of the 41-story building, which includes 28 stairwells, satellite corridors, three basement levels more than 700 feet long, and an assortment of workshops, mechanical and electrical rooms, storage areas, and security rooms.

An expert on emergency evacuation systems and issues, retired California Deputy State Fire Marshal Manny Muniz, said photoluminescent markings have demonstrated their value during a real catastrophe, as well. Installed in World Trade Center stairwells after the February 1993 bombing of the New York City landmark, they played a significant role, an investigating commission found, in why so many people got out after the 9/11 terrorist attacks, before the towers collapsed. "So it has proven itself under the most rigorous conditions," Muniz said. "Since 9/11, we've seen that the reliance on traditional electrical sources, whether it be batteries or electrical sources, is no longer something we can count on. Now we have a safer way to do this, a much safer and environmentally friendly way. It's as close as you can get to fail-safe." The Department of Defense used photoluminescent markings inside the portion of the Pentagon it rebuilt after 9/11, he added.

"Places like New York City, places like Washington, D.C., are really putting a lot of photoluminescence into their buildings," said Richard Einhorn, global business manager for Lumilux, a product group of luminescent pigments from Honeywell Specialty Materials. Although security concerns driven by 9/11 have spurred this usage, U.S. growth in the use of photoluminescent safety signage will be driven more by building code approvals and regulations, he said. The eight-member PL Coalition of photoluminescence manufacturers, which includes his firm and uses the services of Muniz's Sacramento consulting firm, Manny Muniz Associates, LLC, concentrates on amending building and fire codes.

As Einhorn and Muniz noted, safety laws and innovations frequently follow disasters. Muniz said while he was working in the California state fire marshal's office, the state passed legislation (stemming from the MGM Grand fire in Las Vegas in November 1980) that required path markings at the floor level of schools, hospitals, hotels, motels, nursing homes, and public assembly buildings. "The priority effort is to make sure people can identify the exits in smoke," he explained. "There's a very short window of time when a fire starts for people to be able to successfully exit."

He said the new law allowed him to become familiar with various strategies for egress marking, including photoluminescent products. The products use either of two materials, zinc sulfide and strontium oxide aluminate, which have the ability to accumulate energy from ambient light. Like a naturally occurring battery, they store energy and are able to give it off as light.

Strontium oxide aluminate products can hold 10 times more energy and have a useful life that is three to four times longer than zinc sulfide, Einhorn said. While a strontium oxide aluminate product's typical visibility is two to eight hours, a zinc sulfide product is visible for 1.5 to three hours. (This longevity is important because meeting UL 924, the standard to which many PL signage products are tested, requires lettering to be distinguishable at 50 feet for 90 minutes.) Strontium oxide aluminate is very UV stable, while zinc sulfide yellows over time. Zinc sulfide has the advantage of being useful in a water-based system, making possible PL paints, but strontium oxide aluminate powder degrades in water. Einhorn said the two materials allow photoluminescence to be incorporated into a wide variety of products: inks, coatings, plastics, films, ceramics, glass, glazing, and fibers. Strontium oxide aluminate pigment costs five to seven times more than zinc sulfide, but a typical application uses only one-third as much.

Einhorn does not recommend PL for outdoor applications. It is best suited, he said, for applications where the lights can go out suddenly and completely, as though a switch has been turned off.

Part of a Comprehensive Program
The first big U.S. application for photoluminescent signage was in marine safety, Einhorn said. European countries have been using photoluminescent signs far longer, for about 30 years, in airports and large buildings. PL has a $150 million to $200 million market worldwide excluding China, which by itself is a $100 million to $150 million market but uses and produces lower-quality pigments and signs, he added.

Photoluminescent products offer lower lifetime costs and operational advantages, but they are only part of a sound evacuation signage program that also includes electrical signage, Einhorn stressed. "PL has its place. It is not a miracle cure," he said. "It will not, as some people say, glow all night or be something you can read by. That kind of hype really gets on my nerves. . . . I would say you want both systems."

For example, electrical signage is preferable for hallways longer than 50 feet, he said. Where photoluminescent signage makes the most sense is in low-level pathway egress marking. "It's that one extra little help," Einhorn explained, when an emergency evacuation is needed: Hotel occupants may panic, but if there's a photoluminescent map in their room and they open the door to see the path clearly marked, they'll follow it.

Durability and lower installation and maintenance costs are two clear PL advantages, Muniz said. Photoluminescent signage can be installed by a contractor or maintenance worker. Installing electrical signage, however, requires an electrician. U.S. companies spend $1 billion per year to operate electric-powered exit signs, said Muniz. Photoluminescent exit signs are non-toxic, non-radioactive (unlike tritium, which is toxic and radioactive), and consume no electricity.

"We really don't know that there is an expiration date for this. Most manufacturers have a 25-year date on theirs. The durability of the product is incredible," he said. "Basically, the maintenance of these things is just to get the cobwebs off them. Bulbs in an [electrical] exit sign hardly ever get replaced. They'll be out for months" because special bulbs are needed.

"I don't think that electrical signage is going to go away. But I think in terms of market share, you're going to see the photoluminescent materials really start to take over a large market share," Muniz added. "You're seeing it on land, at sea, in the air on airliners, on passenger trains. It's really fascinating the way these dominos are falling into place. It's only started to take off [in safety] in the last three to four years."

Low-Level Markings in Building Codes
The federal General Services Administration, which manages some 8,000 government-owned and -leased buildings in the United States and overseas, included PL signage in its 2003 standard for means of egress. The standard mandates stair identification signs with a background made of photoluminescent material and stair treads incorporating photoluminescent paint or adhesive strips on the leading edge of the tread. Handrails and doorframes also must be marked.

Hotels also are adopting PL, and more and more cities require it in buildings, even old buildings, Muniz said. "There's a major campaign on right now with building codes to require lower level path markings," although the codes won't specify photoluminescent markings, he said.

Muniz has authored additions and changes to numerous codes during his career, and not just to introduce PL into them. Before he retired in 1993, his responsibilities at the fire marshal's office included developing state fire regulations for California. (He worked for the Sacramento Fire Department the previous 13 years.) His code resume includes contributions to NFPA 5000, Building Construction and Safety Code (now in its 2002 edition); UL 924, Emergency Lighting and Power Equipment (Exit Signs); NFPA 101, Life Safety Code (2003 is the current edition); NFPA 1, Uniform Fire Code; and California's Building Standards Code and Health & Safety Code.

A High-End Retrofit
Einhorn said he installed the best PL signage material available in September 2002 in a six-story stairwell and 100 yards of a basement area into a boiler room inside Honeywell International's corporate headquarters in Morristown, N.J. Including signs at every door, rails, arrows on the walls, and safety tape around doorways, it was an extensive, $5,000 demonstration project that could have been done for as little as $1,500, he said.

The signage remains in place and has performed very well, he said. "What you see is, it's very bright. You can clearly see everything very well, without a problem. We've had people call up the maintenance staff asking about the green light in the stairwell when a fluorescent light's gone out. Just in general, it's sort of blended in."

This article originally appeared in the June 2004 issue of Occupational Health & Safety.