Every common hall and stairway in residential occupancies, other than in one and two
family dwellings, shall be lighted at all times with at least a 60-watt standard incandescent
light bulb for each 200 square feet of floor area or equivalent illumination, provided
that the spacing between lights shall not be greater than 30 feet. In other than residential
occupancies, means of egress, including exterior means of egress, stairways shall
be illuminated at all times the building space served by the means of egress is occupied,
and illumination shall remain in the event of a power outage.
