Maximum instantaneous luminous intensity required to produce a vertical illuminance of 2 fc on a wall located at different distances from the signal.
The Fire Protection Research Foundation report: "Performance Objectives for Light Sources Used in Emergency Notification Appliances," was recently published and made available to those interested. The reports authors included J.D. Bullough, Y. Zhu, the Lighting Research Center, and Rensselaer Polytechnic Institute.
LEDs and other innovative energy saving lighting technologies (e.g. fluorescents) are rapidly entering the marketplace and present themselves for application to emergency notification appliances. The existing requirements for the performance and application of visible notification appliances are based on relatively short duration, high peak intensity flashing lights – strobe lights. NFPA 72, National Fire Alarm and Signaling Code, and referenced listing standards define a method for calculating the equivalent or effective intensity of a flashing light source. The calculation method is subjective and does not produce an exact comparison and is intended only to approximate the perceived brightness for direct viewing of the light source. It has worked because all of the lights approved using the standard have all had relatively similar and short pulse durations. Thus, the peak intensities have been relatively similar.
The objective of this project was to develop methods and criteria to evaluate performance of light sources used in emergency notification appliances for inclusion in NFPA 72. Therefore, this report recommends specifications for both direct and indirect signaling as well as identifies gaps in the available information.
The full report can be downloaded for free, as with all Research Foundation reports.