|Photoluminescent Pathway-marking Systems in High-Rise Office Buildings|
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.
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
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
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
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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