Emergency Lighting Design Guide – Legend Viewing Distances

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

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