Exit Signs are required in all Occupancy types except One and Two Family Dwellings (NFPA 101-xx.2.10 and 7.10).

The maximum viewing distance for exit sign is 30 m.

(a) Luminance. Exit and directional signs shall have a luminance on the face of such signs of not less than 5 foot-candles (50 lux). The words used on such signs shall be in block letters at least 150 mm in height with a stroke of not less than 20 mm.

(b) Location. Exit or directional signs, or both, shall be provided at every exit door, at the intersection of corridors, at exit stairways or ramps and at such other locations and intervals as are necessary to provide the occupants with knowledge of the various means of egress available.Exit or directional signs need not be provided for the following:

(1) Any room or building having an occupant load of 50 or less;

(2) Dwellings units in Group R, Division 1 Occupancies;

(3) When approved, the main exterior exit doors obviously and clearly identifiable as exits.

location of exit sign
CTTO image source: https://www.dextragroup.co.uk)

(c) Electrically Illuminated Signs. Exit and exit directional signs which are required to be electrically illuminated shall be lighted with two electric lamps, either one of which shall be sufficient to provide the required luminance on the face of the sign.

NOTE: Radioactive isotope self powered signs with a luminance of not less than 0.02 lamberts during its useful life will be acceptable.

height of exit sign
(CTTO image source: https://www.dextragroup.co.uk)