Means of Egress and Emergency Lighting

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Introduction

The Occupational Safety and Health Administration (OSHA) is responsible for promulgating legally enforceable standards which require the use of practices, means or processes that are reasonably necessary and appropriate to protect employees on the job. OSHA incorporates other standards adopted by standard-producing organizations into their own. OSHA promulgated Subpart E of 29 CFR 1910, Means of Egress, from the National Fire Protection Association NFPA 101-1970, Life Safety Code.

OSHA and the National Fire Protection Association (NFPA) give the general requirements for means of egress. 29 CFR 1910.35 defines a means of egress in this way: "A means of egress is a continuous and unobstructed way of exit travel from any point in a building or structure to a public way and consists of three separate and distinct parts." They are:

1. Exit access—that portion which leads to the entrance of an exit;
2. Exit—that portion which is separated from all other spaces of a building or structure by construction or equipment to provide a protected way of travel to the exit discharge; and
3. Exit discharge—that portion between the termination of an exit and a public way.

OSHA requires that "each exit route be adequately lighted so that an employee with normal vision can see along the exit route". 1910.37(b)(1).

OSHA also requires that "each exit must be clearly visible and marked by a sign reading "EXIT"". 1910.37(b)(2). "Each exit route door must be free of decorations or signs that obscure the visibility of the exit route door." 1910.37(b)(3). "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 identifed by a sign indicating its actual use (e.g., closet)." 1910.37(b)(5).

Exit Sign Specifications

Every sign must have the word "Exit" in plainly legible letters not less than six inches high, with the principal stroke of the letter .75 inches wide (29 CFR 1910.37(b)(7)). (See NFPA 101 7.10 for further specifications.) Where the direction of travel to the nearest exit is not immediately apparent, a sign reading "Exit" or similar designation with an arrow indicating the direction to the exit is required (29 CFR 1910.37(b)(4)).

Requirements for Exit Sign Illumination

NFPA 101 defines the methods of illumination for exit signs:

1. Externally illuminated—the light source is contained outside of the device or legend that is to be illuminated. The light source is typically a dedicated incandescent or fluorescent source;
2. Internally illuminated—the light source is contained inside the device or legend that is illuminated. The light source is typically incandescent, fluorescent, electro luminescent, light-emitting diodes, or photoluminescent;
3. Photoluminescent—the sign is illuminated by self-contained power sources and operates independently of external power sources. (Batteries do not qualify as a self-contained power source.)

   Photoluminescent- The face of the sign must be continually illuminated while the building is occupied. The face of the sign shall be illuminated according to its listing from the face of the sign. The illumination has to be a reliable source as determined by the Authority Having Jurisdiction, AHJ. The AHJ is the ultimate arbiter concerning safety practices and safety equipment for a particular locality. The charging light must be of the same type that is specified on the sign.

   Photoluminescent Signs need a specific type of light and a minimum level of light on the face to assure that the sign will be able to provide adequate illumination in an emergency situation. During illumination the sign shall not be connected to an automatic timer.

   In 2000 the NFPA Life Safety Code was updated and now recognizes certain Photoluminescent Exit signs as an alternative to internally lighted electric powered signs. A photoluminescent sign absorbs light from an activation light source in order to emit light (that is, luminescence). The sign continues to emit light for a time after the activation light source has been removed.

   Photoluminescent Exit signs are in the category of an Internally Illuminated Sign. The signs are permitted, provided they are listed in accordance with UL 924, "Standard for Safety Emergency Lighting and Power Equipment" and meet all the requirements outlined in the criteria from the Life Safety Code 101, 2006 edition parts 7.10.7.2.

Every required exit sign must be suitably illuminated by a reliable light source and be visible in both normal and emergency lighting modes (NFPA 101 2006 7.10.5.1). The illuminated surface value of the exit sign should have a value of not less than five foot-candles (29 CFR 1910.37(b)(6)). NFPA 101 2006 7.10.5 has the same requirement (5 foot-candles) for internally and externally illuminated signs, with exceptions made for approved self-luminous or electro luminescent signs that provide evenly illuminated letters; they must have a minimum luminescence of 0.06 foot lambert as measured by a color-corrected photometer.

City of New York Photoluminescent Markings

New York City Local Law #26: As of July 1, 2006, all office buildings 75 feet in height or higher must have installed photoluminescent markings on doors leading to exits and in exit stairs. This is in accordance with amended Local Law 26 of the Building Code of the City of New York, section 27-383 (Photoluminescent Marking) with the addition of section 27-383.1 (Signage Where Egress Path is not Clear). These markings will be in addition to, and not as a replacement for, any existing required exit and/or directional signage.

These requirements, along with the technical specifications can be found on the Department of Buildings website: www.nyc.gov/buildings.

For guidelines to installation of exit signs and markings to comply with the NYC Local Law #26, click here.

Requirements for Emergency Lighting

NFPA 101, Life Safety Code 2006, section 7.9, describes the requirements for emergency lighting. (Emergency lighting is not specifically required for all occupancies. Refer to NFPA 101 2006, UL 924 and local municipal building codes for specific requirements of your occupancy.) Emergency illumination (when required) must be provided for a minimum of 1.5 hours in the event of failure of normal lighting. The emergency lighting must be arranged to provide initial illumination of not less than an average of one foot-candle and a minimum at any point of 0.1 foot-candle measured along the path of egress at floor level. These levels can decline to a minimum of 0.6 foot-candle average and 0.06 foot-candle at any one point at the end of emergency lighting time (1.5 hours). The maximum illumination at any one point can be no more than 40 times the minimum illumination at any one point to prevent excessively bright and dark spots (NFPA 101 2006 7.9.2.1).

The emergency lighting system must be arranged to provide illumination automatically in the event of any interruption of normal lighting (NFPA 101 2006 7.9.2.3).

Definitions and Formulas

The intensity of visible light is measured in units of candles. The rate of flow of light (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.

Sources for More Information

29 CFR 1910.106

29 CFR 1910 Subpart E

National Fire Protection Association, NFPA 77,
Recommended Practice of Static Electricity

NFPA 101 2006

Uniform Fire Code, UFC Div. VIII, Sec. 79.803

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