What’s your “exit strategy” for emergency sign lighting?
Having a good exit strategy means being able to see where you are going during an emergency. OSHA regulations emphasize the importance of adequately lit exit signage to ensure the safe evacuation of employees. These rules require not only that each exit pathway be sufficiently illuminated, but also that the exit signs are clearly visible.
What does OSHA mean by “clearly visible ?”
Despite popular belief that exit signs must be self-illuminated, this is not an OSHA requirement. As long as ambient light, direct light, or emergency lighting can ensure that the exit signs remain visible at all times, then they don’t need to be electronically lighted.
Basic metal or plastic signs can be used; however, they must remain visible even if there is a loss of power. When non-illuminated exit signs are used, employers must still ensure they can be easily seen. This challenge is why many employers opt for electrically wired or battery-operated exit signs with an emergency backup power source. The other option is electroluminescent signage.
What does “illuminated” mean?
OSHA requires in 1910.37(b)(6) that, “Each exit sign must be illuminated to a surface value of at least five foot-candles (54 lux) by a reliable light source and be distinctive in color. Self-luminous or electroluminescent signs that have a minimum luminance surface value of at least .06 footlamberts (0.21 cd/m2) are permitted."
OSHA defines these terms in 1910.34 as:
- Self-luminous — a light source that is illuminated by a self-contained power source (e.g., tritium) and that operates independently from external power sources. Batteries are not acceptable self-contained power sources. The light source is typically contained inside the device.
- Electroluminescent — a light-emitting capacitor with alternating currents that excite phosphor atoms when placed between the electrically conductive surfaces to produce light. This light source is typically contained inside the device.
Here are more definitions to help shed light on OSHA’s requirement:
- Foot-candle — a unit of measurement that lighting professionals used to describe the amount of light that covers a one square-foot surface.
- Lumen — The amount of visible light given off by a specific source.
- Lux — The amount of light output over a given area.
OSHA’s 5 foot-candle requirement is not as bright as one might think. It is relatively dim, providing enough light to move around but not enough to perform detailed or concentrated activities. This would be similar to what you might see in a parking garage.
Key to remember: To ensure employee safety, OSHA requires exit signs to be sufficiently illuminated and visible to workers at all times.