Issue 8: Escape from New York - The Use of Photoluminescent Pathway-marking Systems in High-Rise Office Buildings
By James D. Amy, Jr., P.E.
The first question that someone unfamiliar with these systems typically asks is, "What does photoluminescent mean?" The question that follows is, "What is pathway-marking?" These are both understandable questions as these systems are not common in the United States. However, they are being seen more frequently each passing year.
Photoluminescence is defined by the National Fire Protection Association as, "Having the ability to store incident electromagnetic radiation typically from ambient light sources, and release it in the form of visible light."1 Photoluminescent pigments have been in existence since the early 1900s. However, it is only in the last 20 years that their use has spread from novelty products (e.g., glow-in-the-dark toys) to safety products (e.g., exit signs, pathway-marking, egress signage).
Pathway-marking systems are commonly encountered in commercial aircraft (termed "aisle marking"), in commuter trains, on cruise ships and in buildings. Pathway-marking systems identify the egress paths with markings close to the floor. They are intended to be used in emergency situations. The emergency can be a power failure, a fire, an earthquake, a terrorist attack or other event that compromises overhead lighting or signage. See Figure 1.
Background
The appearance of pathway marking in the Untied States has been sporadic and typically the result of a tragic fire. A timeline of developments is provided below.
- Late 1980s - Pathway marking required on commercial aircraft in response to FAA investigations into aircraft fires and crashes where smoke obscured exits and signs placed near the cabin ceiling.
- 1984 - Haunted house fire at Great Adventure Amusement Park in New Jersey kills eight. The National Fire Protection Association's Life Safety Code (NFPA 101®) is subsequently modified to require that special amusement buildings have directional exit marking and recommends that consideration be given to placing it on or near to the floor.
- 1990 - Scandinavian Star cruise ship fire kills 158, many of whom are unable to find exits because smoke obscures overhead lighting and exit signage. The International Maritime Organization (IMO) passes a regulation in 1993 requiring that all cruise ships and ferries be fitted with pathway-marking systems by October 1997. See Figure 2.
- 1993 - World Trade Center bombing kills six and injures more than 1,000. The bomb knocks out all emergency power, including emergency lighting, and the stairs are left in complete darkness, greatly complicating egress. One recommendation that resulted from the task force investigation into the bombing was to provide a photoluminescent pathway-marking system in the stairs of both towers. The Port Authority of New York and New Jersey subsequently installed the systems. See Figure 3.
- 1999 - American Public Transit Association (APTA) releases guidelines for providing pathway marking on commuter trains to be installed by 2006.
- 2001 - September 11th attack results in the collapse of the World Trade Center towers. While battery-powered emergency lights in the stairs remained operative for much of the time prior to the building collapses, occupants report that the photoluminescent pathway-marking assisted them in their movement. In the Pentagon, some occupants are unable to find their way out because of the massive fire that ensued after Flight 77 slammed into the building. Renovations to the Pentagon include the addition of a photoluminescent pathway-marking system to enhance egress.
- 2003 - United Nations voluntarily installs a photoluminescent pathway-marking system in their Manhattan complex.
- 2004 - City of New York passes Local Law 26, which includes a requirement for all high-rise office buildings in the city to be fitted with a photoluminescent pathway-marking system in the stairs. Systems are required to be installed by July 2006. Guidelines for installation and approval are developed and released as Reference Standard 6-1
(RS 6-1).
Owners faced several challenges in meeting the New York City photoluminescent pathway marking requirement. Listed below are some of the issues raised by designers, installers, regulators and owners as a result of their experiences.
1. Lack of Knowledge about Systems
The lack of knowledge regarding these systems was not limited to building owners but extended to system installers. Few had experience with these systems prior to the requirement being passed. While the New York City Department of Buildings (NYCDOB) went to significant lengths to educate the public, alternative sources of information were mainly limited to the manufacturers and distributors of the products themselves. In this narrow field, few outside of the photoluminescent industry were knowledgeable about the materials or their applications. Therefore, when owners looked for guidance, their sources of information were themselves not experts in the field.
2. Installing an Approved System
At the time of the passage of Local Law 26, there were several existing standards available relating to the design and approval of pathway-marking systems. However, NYCDOB developed its own standard, RS 6-1. It also decided that only photoluminescent materials would be acceptable. Electrically powered pathway-marking systems require external power to remain lit, while systems based on photoluminescent technology do not. Photoluminescent systems depend instead on the ambient light source to be powered prior to an emergency. However, once the emergency has begun, it is not possible for properly charged photoluminescent pigments to fail to emit the energy they have absorbed as light.
NYCDOB expended a great deal of effort in developing RS 6-1 and became well-schooled on the subject of photoluminescent pathway-marking systems. However, its decision to develop a standard reduced the time available to owners to install a compliant system before the deadline. Some owners installed systems prior to the release of RS 6-1. This resulted in modifications being required for noncompliant systems.
NYCDOB approves of systems through its Materials and Equipment Acceptance (MEA) process. Approval involves testing a system in accordance with RS 6-1 at a lab recognized by NYCDOB. The testing process is lengthy, and many approvals required multiple submissions prior to approval being granted. The majority of the approvals issued were dated between August and November 2005, which left less than a year for building owners to choose a system and have it installed.
Given the estimated 1,800 buildings affected, this would have translated into five buildings being completed every day for a year. Not surprisingly, many buildings were not in compliance on July 1, 2006, and systems are reportedly still being installed at this time.
3. Lighting Conditions in Existing Stairs
The charging of photoluminescent pathway-marking systems primarily depends on the type of ambient light provided, the intensity of that light incident on the material, and the duration that that light is provided.
The reason that the type of ambient lighting is relevant is because photoluminescent pigments are charged more readily by light at the ultraviolet end of the spectrum than at the infrared end of the spectrum. Fluorescent lights generally emit a spectrum that contains more light in the ultraviolet end of the visible spectrum than do incandescent lights. Therefore, given equal intensity ambient lighting, a photoluminescent pathway-marking system charged by fluorescent light emits more light than if it is charged by an incandescent light.
In New York City, the building code requires a minimum light level of two footcandles (21 lux) in stairs, but does not specify the light type. Therefore, it was necessary for RS 6-1 to assume that the charging light might be incandescent. The effect of this assumption is that the photoluminescent pathway-marking systems will perform at the minimally accepted level if charged by two footcandles (21 lux) of incandescent light, but will perform at an increased level should the stair be equipped with fluorescent lights providing two footcandles (21 lux) of ambient light at the floor.
The luminance of photoluminescent pigments is also dependent on charging duration. The longer they are charged, the more light they will emit. However, a common trait of photoluminescent pigments is that beyond 120 minutes of being charged, there is very little corresponding gain in luminance. As a result of this phenomenon, RS 6-1 requires that photoluminescent pathway-marking systems operate for 90 minutes after being charged by two footcandles (21 lux) of ambient light for 120 minutes.
As installers began surveying buildings in New York, it became clear that the stairs in many high-rise office buildings in New York City do not meet the two footcandle (21 lux) minimum illumination requirement mandated by the building code. The NYCDOB began to receive questions from owners and installers as to what should be done about ambient light levels less than two footcandles (21 lux). While it was not the intention of the pathway-marking requirement to also require an upgrade in lighting, the response to this frequently asked question was that the lighting should at least meet the minimum mandated by the building code. Otherwise, in the case of stairs lit by incandescent lights, the photoluminescent pathway-marking systems would not be adequately visible at the end of the 90-minute emergency period.
Another issue that arose was that some buildings were equipped with motion detectors that powered up the lights only if someone entered the stairs. Since the photoluminescent pathway-marking systems depend on ambient light being provided to charge them, the use of motion detectors such as these is prohibited.
4. Unfavorable Surface Conditions in Existing Stairs
Photoluminescent pathway-marking systems are mounted on the floors, walls, doors and door frames in the stairs. The materials are either mechanically fastened or depend on an adhesive. While mechanically fastened products are relatively unaffected by the condition of these surfaces, adhesives are heavily influenced. In many buildings in New York, the stairs had to be thoroughly cleaned, or even painted, to provide an acceptable surface for the mounting of the materials. This action undercut the financial advantage of using the lower-cost adhesive-backed systems. Additionally, where proper surface preparation was not provided, adhesive-backed materials frequently came away from the surface, resulting in additional effort on the part of the installer to reinstall system components on properly prepared surfaces. Prudent owners required a warranty period for the system for one or more years and are protected should adhesive-backed materials come away from the surface over time.
Jim Amy is with Rolf Jensen & Associates.
1NFPA 101®, Life Safety Code, National Fire Protection association, Quincy, MA, 2006.
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