Proper Placement and Visibility Are Essential for Emergency Evacuation
Why Are Exit Signs So Important?
The answer may seem obvious, but people often do not appreciate the importance of exit signs. When there is an emergency in a building, all occupants and visitors must be informed of the most efficient way to exit the building. Not every person is familiar with a building’s layout. Visitors to the Capitol or employees who are in a different part of the complex other than their normal work area will rely on exit signs to assist in locating the closest, safest way out of the building in the event of an emergency evacuation. If smoke affects visibility, exit signs may be critical in finding the way to safety. To enable the evacuation of occupants and visitors in the most efficient manner, certain rules must be followed when designing and installing exit signs.
What is a Compliant Exit Sign?
Visibility
The Life Safety Code, NFPA 101, requires a minimum level of visibility for exit signs. The letters require a minimum height not less than six inches (150 mm), the width of the strokes of the letters not less than three-fourth of an inch (19
mm), the width of the letters not less than two inches (51 mm) except the letter I, and the spacing between the letters to be not less than three-eighth of an inch. Therefore, the exit sign shown in Figure 1, a temporary exit sign, is not compliant. Occupants and visitors exiting the building may not be able to see this exit sign during an emergency because of decreased visibility due to smoke or loss of illumination.
Illumination
All exit signs must be suitably illuminated by a reliable light source as required by NFPA 101. Shown in Figure 2 is an externally illuminated exit sign. When the power to the building fails, the Exit sign may not be able to provide the required 5 ft-candle illumination. To address this problem, exit signs are often internally illuminated by wiring them into emergency standby power. Other exit signs, such as tritium and photo-luminescent, are energy efficient and do not require hard wiring. But both still require a constant external light source of 5 ft-candle in order to charge.
