What is the Law? Deciphering UL924 versus NFPA Standards
UL 924 is the standard for Exit Signs, Emergency Lighting, and Power Equipment that uses less than 600 volts of electricity to operate. The equipment under this code automatically illuminates and/or powers critical areas and equipment in the event of electrical failure. UL 924 is a nationwide standard that is separate from state codes. For example, UL 924 will allow both green and red Exit signs, as long as the mounting, lettering, and illumination complies with UL standards.
UL 924 standards
The signs color, however, is subject to state and local codes separate from UL standards. Since 2003, UL (Underwriters Laboratories) have had new criteria for photoluminescent signs. Because of this new standard, it is easy to install safe, compliant, photoluminescent signs in your establishment. UL 924 stadards require, for example, that photoluminescent signs must be visible from a distance of at least 50 feet for at least 90 minutes of complete darkness. UL performs Observational Visibility Tests to administer these standards.
UL 924 colors and display
The UL standard color for Exit signs used to be red, but green is increasingly popular along the West coast and internationally. Both colors are UL compliant; however, state and local codes usually mandate one or the other, depending on your location. For more information about your local codes, click here. Exit Sign Letters must be a least 6'' high. The stroke (letter width) should be 3/4?, and the space between each letter must be 3/8?. If one chooses a larger Exit Sign, the Exit Sign must increase proportionally in size to assure that the Exit Sign is legible from a distance. UL also requires self-luminating, radioactive Tritium signs to include a date of replacement on the sign. Sine photoluminescent signs do not need to be replaced, they do not require this addition.
About the NFPA
The NFPA is an international, not-for-profit organization whose goal is to reduce the burden of fire and hazards by reccommending codes and standards, and a wealth of research that is universally accepted. You will often see NFPA-reccommended graphics that are very familiar and widely understood. For more information about the NFPA, click here. In 2000, the newest editiion of the NFPA Life Safety code advocated the use of photoluminescent signs that are continually exposed to a minimal light level when the building is occupied. This new guideline makes it easy to comply with NFPA regulations with photoluminescent safety signs.
Abiding by UL 924 codes (which is required) and NFPA standards (for ?accredited facilities?) is your most powerful protection in the face of a fire emergency.