Part 4 – Legend Viewing Distances
BS5266 and BS5499 define the viewing distances for exit signs, these are spilt into two categories;
a. INTERNALLY illuminated exit signs
b. EXTERNALLY illuminated exit signs
The calculation is as follows:
Viewing Distance (D) = The overall height of legend (H) x Factor (F)
NOTE
- You must remember the legend has a 5mm transparent border.
- The sign height is the printed area/safety colour green only, the below image helps explain this.
Things to consider:
- Escape route signs should be cleaned and visually inspected at regular intervals
a. INTERNALLY illuminated exit signs
Examples of internally illuminated exit signs:
Internally illuminated signs have a multiplying factor (F) of 200.
Example: Legend green height is 135mm
= 135mm x 200
= 27,000mm
= 27M
b. EXTERNALLY illuminated exit signs
Examples of externally illuminated exit signs:
Externally illuminated signs have a multiplying factor (F) of 100.
Example: Legend green height is 135mm
= 135mm x 100
= 13,500mm
= 13.5M