To ensure that all employees understand
the general procedures to
be followed in an emergency, an
OSHA-based emergency action plan
must include a well-marked escape
route.
An exit route is a continuous and unobstructed
path of exit travel from any
point within a workplace to a place of
safety. According to 29 CFR 1910.36(a),
exit routes must be permanent, and should
consist of the following three parts:
• Exit access – the portion of an exit route
that leads to an exit;
• Exit - portion of an exit route that is generally
separated from other areas to provide
a protected way of travel to the exit
discharge;
• Exit discharge - part of the exit route that
leads directly outside or to a street, walkway,
refuge area, public way, or open
space with access to the outside;
• Each exit route must be adequately
lighted so that an employee with normal
vision can see along the exit route. Each
exit must be clearly visible and marked
by a sign reading “Exit”;
• Each exit route door must be free of
decorations or signs that obscure the
visibility of the exit route door;
• If the direction of travel to the exit or exit discharge is not immediately apparent,
signs must be posted along the exit
access indicating the direction of travel
to the nearest exit and exit discharge.
Additionally, the line-of-sight to an exit
sign must clearly be visible at all times;
• Each doorway or passage along an exit
access that could be mistaken for an exit
(such as a closet) must be marked “Not
an Exit” or similar designation, or be
identified by a sign indicating its actual
use;
• Each exit sign must have the word
“Exit” in plainly legible letters not less
than six inches (15.2 cm) high, with the
principal strokes of the letters in the
word “Exit” not less than three-fourths
of an inch (1.9 cm) wide;
• During new construction, employees
must not occupy a workplace until the
exit routes required by this subpart are
completed and ready for employee use
for the portion of the workplace they
occupy;
• During repairs or alterations, employees
must not occupy a workplace unless the
exit routes required by this subpart are
available and existing fire protections are
maintained, or until alternate fire protection
is furnished that provides an equivalent
level of safety.
• Employees must not be exposed to hazards
of flammable or explosive substances
or equipment used during
construction, repairs, or alterations, that
are beyond the normal permissible conditions
in the workplace, or that would
impede exiting the workplace.
In accordance with NFPA 101, Life
Safety Code, which has undergone recent
changes regarding exit path markings,
signs shall have a background made of photoluminescent material complying
with ASTM E 2072-00 as a minimum
standard.
• The signs shall be a minimum size of 12
inches by 12 inches.
• The large letter and number type shall
be a minimum of 1-1/2 inches tall.
• The small letter and number type shall
be a minimum of 9/16” tall.
• The directional arrows shall be a minimum
of 1-3/8 inches tall.
• Letters and numbers on the signs shall
have a width-to-height ratio between 3:5
and 1:1; and a stroke width-to-height ratio
between 1:5 and 1:10.
According to a white paper from Graphic
Products titled “Photoluminescent Labels,
Signs, and Path Markings,” photoluminescent
marking is being required by a
growing number of municipalities in the wake of studies of the evacuation of the
World Trade Center.
According to Graphic Products, photoluminescent
technology provides a way to
clearly mark exit pathways and provide
emergency information that will be visible
in smoky conditions and when lights
fail. Since no power is required, photoluminescent
labels and signs provide a reliable
and safe means to mark pathways,
identify hazards, provide directions, and
provide needed information during a
power outage or an emergency.
What Is Photoluminescent
Technology?
Photoluminescent labels and signs are
commonly known as “glow-in-the-dark.”
They absorb energy from a light source
during normal conditions. When the light
source is removed they will glow, serving
as a reliable source of information when
lighting fails due to power outages, obstruction
from smoke, or in other types of
emergencies. They are commonly used to
mark exit pathways throughout a building
to orient people during evacuation by
guiding their steps and hand-placement.
Photoluminescent signs and markings are typically placed in multiple locations,
including along walls within a foot and a
half from the floor. Photoluminescent technology
is not intended to illuminate an area,
but to outline an area and provide information.
Photoluminescent labels and signs can
be recharged over and over again and, for
indoor applications, can last for decades.
How Does Photoluminescent Work?
Photoluminescent technology involves
mixing light-storing crystals into labeling
and sign making materials. The crystal
that is used is strontium oxide aluminate,
which provides a stronger light and lasts
longer than zinc sulfide, the material most
often used in “glow-in-the-dark” toys.
Three key factors affect luminance:
• The type of light used to charge photoluminescent
labels and signs. Fluorescent
and halogen lights charge
photoluminescent material more effectively
than incandescent lights. Sunlight
is the most effective light for charging
photoluminescent materials, but the UV
in sunlight causes deterioration of the
sign or label. Typical outdoor life for a
photoluminescent label is three years,
whereas labels used indoors can last for twenty years or more;
• Light intensity where the label or sign is
located (measured in lux or foot candle).
The greater the intensity, the faster the
charging rate. As little as 5-foot-candles
(the amount of light that comes from a
15 watt bulb) are needed to charge strontium
oxide aluminate photoluminescent
labels and signs;
• Illumination charge time (in minutes).
The greater the intensity of the light, the
less time required to fully charge the label
or sign. Typical recharge times are
in the range of 30-60 minutes. This will
provide a full eight hours of glowing.
NFPA 101 7.2.2.5.5.11 requires that exit
enclosures where photoluminescent materials
are installed be continuously illuminated
for at least 60 minutes prior to
periods when the building is occupied.
Photoluminescent signs and markings
are at their very brightest for the first ten
minutes, and then luminance begins to
slowly decrease. Despite the decrease,
however, the human eye inherently adapts
to the darkness at the same time. Therefore,
a person’s eyes will have compensated
enough to essentially eliminate any
noticeable difference in luminance. ❑
