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January 06, 2017
LED Fire Notification Devices: Polar Light Distribution

The basic premise of Indirect Viewing for Visual Signaling Appliances is that it is unlikely during an emergency event any of the building occupants will be looking directly at the appliance. Therefore, detection by peripheral vision and / or reflection becomes critical. This is the reason for the Polar Plotting requirement in section 27.1.3 a) of ANSI/UL 1971.

Traditional Strobe technology utilized a Xenon flash tube in front of a folded reflective surface. While this technology was effective in meeting the basic intent of Signaling for the Hearing Impaired, it was very inefficient.

There are two reason for this inefficiency (limitation):

  1. Although the xenon fast tube develops a large amount of light energy, it is basically a point source and most of the light is emitted on axis.
  2. A simple reflector is very limited in its ability to effectively disperse the light from the point source and therefore the light source must be significantly overdriven to achieve the minimum required output over the entire specified plot area. This makes for an extremely bright on axis while marginally effective device at the edges. (See Figure 1).

The Light Engine America patented approach is to utilize multiple light sources coupled with complex lenses that effectively distributes the light where needed. Since each light source and its associated lens covers a dedicated portion of the required polar distribution, no individual source needs to be overdriven to compensate for another sector. This results in a distribution that very closely matches the ANSI / UL 1971 polar plotting requirement (see Figure 2) while concurrently consuming considerably less current from the Notification Appliance Circuit (NAC).

Light Engine is proud of the research work we have undertaken in support of advancing the use of LED technology in fire notification devices. We believe that through comprehensive research and the generation of supporting in-depth data, Light Engine is able to design and manufacturer safe products today using tomorrow’s technology first.

For any questions or comments about the use of LED technology and the advancements in Fire Notification device efficiencies, please email: or visit our website at

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