Guide to Exit Lighting
It is important for exit ways to always be properly lighted. Not only should the regular exit lighting be maintained up to standard, but emergency exit lighting must also be ready in case of a crisis situation. Check out PE Facts to find out the specific requirements for Exit Lighting.
It is the duty of the Occupational Safety and Health Administration (OSHA) to circulate legally enforceable standards that involve the use of practices, means or processes that are reasonably appropriate and needed in order to protect employees at work. OSHA includes standards used by other standard-producing organizations in their own. OSHA promulgated Subpart E of 29 CFR 1910, Means of Egress, from the National Fire Protection Association NFPA 101, Life Safety Code.
OSHA and the National Fire Protection Association (NFPA) propose requirements for exit ways. In 29 CFR 1910.35, means of egress is defined as: "a continuous and unobstructed way of exit travel from any point in a building or structure to a public way and it consists of three separate and distinct parts." They are:
- Exit access —the section which leads you to enter an exit;
- Exit —the segment which is separate from all other parts of a building or structure by construction or equipment in order to offer a protected way of travel to the exit discharge; and
- Exit discharge —the portion between the end of an exit and the outside public.
Under 1910.37(b)(1)., OSHA requires that "each exit route be adequately lighted so that an employee with normal vision can see along the exit route".
Under 1910.37(b)(2)., OSHA also requires that "each exit must be clearly visible and marked by a sign reading ‘EXIT’". 1910.37(b)(3). states that, "each exit route door must be free of decorations or signs that obscure the visibility of the exit route door". Under 1910.37(b)(5)., "each doorway or passage along an exit access that could be mistaken for an exit must be marked ‘NOT AN EXIT’ or similar designation, or be identified by a sign indicating its actual use (e.g., closet)”.
All signs must have the word "Exit" written clearly, with letters no less than six inches high, and the principal stroke of the letter .75 inches wide (29 CFR 1910.37(b)(7)) (See NFPA 101 7.10 for further specifications.). If the closest exit is not directly visible, a sign reading "Exit" or a similar title, with an arrow demonstrating the way to the exit is mandatory (29 CFR 1910.37(b)(4)).
Requirements for Exit Sign Illumination
NFPA 101 dictates the illumination standards for exit signs:
- Externally illuminated —the light source is contained outside of the illuminated sign. The light source is usually a dedicated incandescent or fluorescent bulb;
- Internally illuminated —the light source is contained inside the illuminated sign. The light source is generally incandescent, fluorescent, light-emitting diodes, electro luminescent, or photo luminescent;
- Photo luminescent —self-contained power sources that operate independently of external power sources illuminate the sign. (Batteries are not a self-contained power source.)
Photo luminescent- If the building is occupied, the face of the sign must be constantly illuminated. The face of the sign must be illuminated according to its listing from the face of the sign. The illumination source has to be reliable, as determined by the Authority Having Jurisdiction, AHJ. The AHJ is the ultimate authority when it comes to safety practices and safety equipment for a particular locality. It is necessary that the charging light is the same type that is specified on the sign.
Photo luminescent Signs need a certain type of light and a minimum level of light on the face to guarantee that the sign will project adequate illumination in an emergency situation. During illumination the sign shall not be connected to an automatic timer.
The newly updated NFPA Life Safety Code now acknowledges particular Photo luminescent Exit signs as acceptable alternatives to internally illuminated electric powered signs. In order to emit light, photo luminescent signs absorb light from an activation light source. After the activation light source has been removed, the sign will continue to emit light for a period of time.
Photo luminescent Exit signs are classified as internal illumination signs. These signs are allowed, as long as they are listed in accordance with UL 924, "Standard for Safety Emergency Lighting and Power Equipment" and comply with all the requirements outlined in the criteria from the Life Safety Code 101, parts 7.10.7.2.
All exit signs must be properly illuminated by a dependable light source and must be easily visible in both normal and emergency lighting settings (NFPA 101, 7.10.5). The lighted surface value of the exit sign should have a value of at least five foot-candles. (29 CFR 1910.37(b)(6)).NFPA 101, 7.10.5 has the same requirement (5 foot-candles) for internally and externally illuminated signs, with exceptions made for any electro luminescent or self-luminous signs that are determined to provide equally illuminated letters; they must have a minimum luminescence of 0.06 foot lambert as measured by a color-corrected photometer.
Requirements for Emergency Lighting
The requirements for emergency lighting are described in NFPA 101, Life Safety, section 7.9. (All occupancies do not specifically require emergency lighting. Refer to NFPA 101, UL 924 and local municipal building codes for the exact requirements of your occupancy.) If required, Emergency illumination must be available for at least 1.5 hours in the case that normal lighting is lost. It must be able to produce initial lighting with the intensity of about one foot-candle and at any point a minimum of 0.1 foot-candle measured at floor level along the path of egress. These levels can decrease to a minimum of 0.6 foot-candle average and 0.06 foot-candle at any point at the end of the emergency lighting time (1.5 hours). In order to prevent excessively bright and dark spots, the maximum illumination at any point can be no more than 40 times the minimum illumination at any point (NFPA 101 7.9.2.1).
The emergency lighting system must be designed to automatically illuminate in the event of any interruption of normal lighting (NFPA 101 7.9.2.2).
Definitions and Formulas
The intensity of visible light is measured in units of candles. The rate of flow of light, or luminous flux, is measured in lumens. One lumen is the flux on one square foot of a sphere, one foot in radius with a light source of one candle at the center, and radiating uniformly in all directions. One lux is a unit of illumination equal to one lumen per square meter. Foot-candle is the direct measurement of visible radiation falling on a surface. Foot lambert is the unit measure of physical brightness on any surface emitting or reflecting visible light.
| Foot-candles | X 10.764 | = | lumens/sq. meter |
| Foot-candles | X 10.764 | = | lux |
| Lumens/sq. ft. | X 1 | = | foot-candles |
| Lumens/sq. ft. | X 10.764 | = | lumens/sq. meter |
| Lumens | X 0.07958 | = | spherical candle power |
| Lux | X 0.0929 | = | foot-candles |
| Lambert | X 0.3183 | = | candles/sq. cm |
| Lambert | X 295.720 | = | candles sq. ft. |
| Lambert | X 1 | = | lumens/sq. cm |
Sources for More Information
National Fire Protection Association, NFPA 77,
Recommended Practice of Static Electricity
Please Note: The information contained in this publication is intended for general information purposes only. This publication is not a substitute for review of the applicable government regulations and standards, and should not be construed as legal advice or opinion. Readers with specific questions should refer to the cited regulation or consult with an attorney.
