(1)
Except as permitted in Sentences (3) and (4), openings through guards shall be of a size that prevents the passage of a spherical object having a diameter of 100 mm. (See Note A-9.8.8.5.(1) and (3))
(2)
Except for guards that serve industrial occupancies, the triangular openings formed by stair risers, stair treads and the bottom element of a required guard shall be of a size that prevents the passage of a 150 mm diam sphere.
(3)
Except where they serve storage garages, guards in industrial occupancies are permitted to consist of
(a)
a top railing, and
(b)
one or more horizontal intermediate rails spaced such that the size of the openings through the guard prevents the passage of a spherical object having a diameter of 535 mm. (See Note A-9.8.8.5.(1) and (3))
(4)
Openings through any guard that is not required by Article 9.8.8.1. and that serves an occupancy other than industrial occupancy, shall be of a size that
(a)
prevents the passage of a spherical object having a diameter of 100 mm, or
(b)
permits the passage of a spherical object having a diameter of 200 mm. (See Note A-9.8.8.5.(4))