(1) Stairways which penetrate only a single deck
shall be protected at least at one level by at least "B-0" class divisions
and self-closing doors. Lifts which penetrate only a single deck shall
be enclosed by "A-0" class divisions with steel doors at both levels.
Stairways and lift trunks which penetrate more than a single deck
shall be enclosed by at least "A-0" class divisions and protected
by self-closing doors at all levels.
(2) All stairways shall be of steel frame construction
except where the Administration permits the use of other equivalent
material.