Photoluminescent FAQs

Photoluminescent FAQ

Q. What are photoluminescent, or glow-in-the-dark exit path markings?

A. Photoluminescent (PL) exit path markings are a relatively new type of Life Safety Improvement for a wide variety of applications including Commercial and Government Buildings, as well as sea, land and air vehicles. PL exit path marking systems are even in use in the International Space Station. They can provide life-saving exit guidance to all residents, employees and tenants during an emergency evacuation.

Q. How do Photoluminescent materials work?

A. Photoluminescent, also known as "glow-in-the-dark", materials incorporate inorganic phosphors into a carrier or substrate. The substrate might be a solvent-based or water-based paint, a magnetic- or adhesive-backed tape, a plastic extrusion, an acrylic or polyurethane casting or injection molded item, or a vinyl film. These PL phosphors absorb light in the visible and ultraviolet wavelengths and release visible light in what is often termed an “afterglow.” This afterglow luminance decays over time. The “Extinction Time” is the time for the luminous intensity of the afterglow to decline to the lower luminance limit of human perception for dark-adapted eyes (032 mcd/m²). More important is the “Functional Time.” For products sold by DHi, the minimum Functional Time is 8 hours, more than enough for everyone to exit. Dark adaptation of the viewers’ eyes results in a perceived brightening of the material. In all cases, the critical performance characteristics are the Luminance Performance (i.e., the initial brightness of the material and how long it will glow). PL materials will continue to perform even if damaged.

Q. How long does it take to charge DHi’s AfterGlo® Brand Photoluminescent Safety Paint and AfterGlow® Brand Photoluminescent Safety Products?

A. DHi’s AfterGlo® Brand PL Safety Paint and AfterGlow® Brand PL Safety Products are charged in minutes by UV light sources including:

  • The sun (best source for charging)
  • Electric light sources such as fluorescent/incandescent lights, black lights or flashlights

Once fully charged by a light source, the afterglow remains visible for 8+ hours after the light source is removed. A full charge can be achieved by:

  • 3-4 minutes of ultraviolet (black) light, or
  • 7-8 minutes of direct sunlight, or
  • 21-23 minutes of fluorescent light, or
  • 24-26 minutes of incandescent light

Q. Why should I improve my buildings exit path marking system?

A. Even today, most buildings and facilities have insufficient emergency lighting despite meeting local codes. Electrically illuminated EXIT signs located at door or ceiling level are frequently obscured in a fire by heavy smoke. Improper system maintenance and inadequate maintenance oversight can result in an exit path marking system with less than 100% reliability. Electrical systems (primary and backup) can fail during an emergency event due to damage from heat and firefighting water. When the Pentagon was attacked on 9/11, they had to turn the back-up power off to prevent firefighters and other first responders from being electrocuted. Photoluminescent exit path markings are always there. They don’t rely on external power and don’t require regular maintenance. There are good economic benefits as well for replacing existing electrical exit signs with UL 924 listed photoluminescent exit signs.

Q. My property is not a government building. Why do I need to worry about terrorism?

A. These concerns exist for many commercial buildings, too. Commercial sites are often potential targets for terrorist attacks. They are often seen as softer targets. High-profile commercial buildings in New York City and the Washington, DC Metropolitan Areas may be particularly vulnerable because of international visibility and the presence of foreign and domestic news agencies. Also, many of these facilities have a large transient population, many of whom are unfamiliar with the infrastructure.

Q. Are there different grades of Photoluminescent materials and are they environmental friendly?

A. You may be familiar with photoluminescent materials from your childhood. Many of us remember the glow-in-the-dark Halloween skeleton that stopped glowing in a few months. That was made from what is called “Novelty Grade” PL material. The phosphor was zinc sulfide (ZnS) and it quickly lost its ability to be recharged. All products sold by DHi use strontium aluminate (SrAl), a much newer “Safety Grade” phosphor that is non-toxic and non-radioactive, and retain their ability to be recharged and glow brightly for many, many years. Typically, the luminance life span is 30+ years for safety-grade strontium aluminate (SrAl) materials and only 3-4 years for novelty-grade zinc sulfide (ZnS) materials. Even among products using these newer phosphors, there is much variability. Generally “brighter is better,” but it is also more expensive. The key here is specifying the right product with the optimum balance between performance and cost. Durability is largely a function of the substrate selection. Performance is also affected by the cleanliness of the material. A surface layer of dirt or grime can block light (both the light used to charge the material and the afterglow emitted), so materials should be easy to keep clean…a consideration in the design of the installation.

Q. Will PL exit path markings meet my building code?

A. A word on Building Code Requirements:

NYC passed Local Law 26-04 that required PL marking systems in stairwells of all Class E commercial buildings over 75 feet tall within the city. This law applied to new construction starting on July 1, 2005. It also applied retroactively to over 1,600 existing buildings commencing on July 1, 2005 and to be fully implemented by June 30, 2006.

On May 24, 2007 the International Code Council voted to modify the International Building Code to include the NYC standard for photoluminescent path markings in the stairwells of most new high-rise buildings over 75 feet in height.

Many Building and Fire Codes are based upon the IBC 2003 and IFC 2003, respectively.

IBC 2009 (pending publication) Section 403.16 now requires Exit Path markings, and Section 411.7 now requires Exit signs and directional path markings (IAW UL 1994).

NFPA 2009 Section defines installation guidelines for Exit Stair Path Markings where required in Chapters 11 thru 42.

In all cases, DHi advises you to check with your local authorities. We can assist you in answering specific questions that result.

Q. What does the International Building Code (IBC) say about photoluminescent exit signs?

A. IBC and IFC 2003, sections 1011 address exit signs:

1011.4 – Internally illuminated exit signs shall be listed and labeled and shall be installed in accordance with the manufacturer’s instructions and Section 2702. Exit signs shall be illuminated at all times.

1011.5.3 – Approved exit sign illumination means that provide continuous illumination independent of external power sources for a duration of not less than 90 minutes in case of primary power loss, are not required to be connected to an emergency electrical system.

2007 Supplement to the IBC section 1011.4 – Internally illuminated exit signs. Electrically powered, self-luminous and photoluminescent exit signs shall be listed and labeled in accordance with UL 924 and shall be installed in accordance with the manufacturer’s instructions and Section 2702. Exit signs shall be illuminated at all times.

Q. Can photoluminescent exit signs save me money?

A. Exit signs are required by code and sometimes law. The vast majority of exit signs in use in the U.S. today are electrically powered. Electrical exit signs consume electricity 24 hours a day, 7 days a week and 365 days a year. They require frequent maintenance and component replacement. While new exit signs are limited to 5 watts per illuminated face, there are tens of millions of existing exit signs that consume far more electricity. In a single year, under the EPA’s current recommended standard, each electrically-powered exit sign can consume as much as 88 kilowatt-hours of electricity – ($8.80 at $0.10 per kilowatt-hour). Older types of electrically-powered exit signs can consume as much as 350 kilowatt-hours of electricity – ($35.00 at $0.10 per kilowatt-hour). Businesses, schools, hotels, hospitals, government facilities and other public buildings pay more than $1 billion every year to power these signs. Every electric Exit sign with a backup battery must be tested 12 times per year. Most exit signs still require manual testing. (Assumes 5 minutes per sign, 12 times per year and $10/hour labor cost.) Bulbs burn out, back-up batteries go dead and LEDs become dim. These parts and the labor to replace them add over $3 Billion more in cost each year. Building operators could be paying as much as $30-50 per exit sign per year just to keep them operating. There are two alternatives to electrically-powered exit signs: (1) tritium signs – these use no electricity, but contain radioactive gas, are expensive, and have a limited useful life along with a high disposal cost, and (2) photoluminescent signs. Underwriters Laboratories (UL) tested and listed photoluminescent exit signs. PL exit signs are:

  • Powered by absorbing ambient, fluorescent, and incandescent light
  • Instantly visible when the ambient light goes out
  • Easily legible at the rated viewing distance after 90 minutes of darkness as required by UL
  • Safe, non-toxic and non-radioactive
  • 100% reliable with an expected lifetime of more than 30 years
  • Not reliant on external power or how well maintenance was performed
  • Non-explosive, so can be used in any environment
  • The ultimate “Green” exit sign

Q. What does Underwriters Laboratories (UL) say about photoluminescent exit signs?

A. UL Listed PL Exit Signs

UL 924, Supplement SG, Photoluminescent Exit Signs, 11 July 2001 revision, addresses construction, legend dimensions, testing procedure, photoluminescent performance, marking, and installation of photoluminescent exit signs.

All PL exit signs sold by DHi meet these UL 924 requirements and are 50, 75 or 100 ft, depending on the exact model.

Q. What specific experience does DHi have with photoluminescent exit path marking systems?

A. DHi offers an unusually wide-range of photoluminescent experience. We believe that DHi offers a really unique capability:

  • We designed the unique PL exit path marking system installed in the Pentagon. This system is called the Low Level Exit Path Marking (LLEPM) system because it incorporates marking near the floor where they wouldn’t be hidden by a layer of dense smoke descending from the ceiling and where they could be seen by someone crawling along the floor. DHi drafted the specifications for the system being installed in the Pentagon.
  • We won a competitive contract (6 companies bid) to provide and install a comprehensive LLEPM system throughout 6.5 million square feet of the renovated Pentagon, the largest photoluminescent signage installation in the U.S. and possibly the world.
  • We assisted the NYC Department of Buildings in the drafting of their specification that requires photoluminescent markings in most high-rise buildings.
  • We are approved by the NYC Department of Buildings to manufacture photoluminescent products to their demanding specifications for use in NYC.
  • We do our own product manufacturing and conversion in Trenton, NC and installation without using sub-contractors.
  • We are one of only two manufacturers who are approved to supply photoluminescent signage to the U.S. Navy.
  • We have developed high performance photoluminescent paint for the Navy to enhance aircraft safety and have extended that research to a line of photoluminescent building safety paint.
  • Significant DHi PL Installations include:
    • Pentagon
    • Eisenhower Executive Office Building (part of the White House complex)
    • 1101 New York Ave., DC
    • Uniformed Services University of Health Sciences
    • Veterans Administration Headquarters
    • Department of Energy (Forrestal Building)
    • Joint Spectrum Center
    • International Monetary Fund
    • Boeing – The National Reconnaissance Office (NRO)