14B.2.6.1 A stairway should be of steel frame
construction except where the Administration sanctions the use of
other equivalent material, and should be within enclosures formed
of "A" class divisions, with positive means of closure at all openings,
except that:
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.1 an isolated stairway which penetrates a single
deck only may be protected at one level only by at least "B" class
divisions and self-closing door(s); and
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.2 stairways may be fitted in the open in a public
space, provided they lie wholly within such public space.
14B.2.6.2 A stairway enclosure should have direct
communication with the corridors and be of sufficient area to prevent
congestion, having in view the number of persons likely to use them
in an emergency. In so far as is practical, stairway enclosures should
not give direct access to galleys, machinery spaces, service lockers,
or other enclosed spaces containing combustibles in which a fire is
likely to originate.
14B.2.6.3 A lift trunk should be so fitted to
prevent the passage of flame from one 'tween-deck to another and should
be provided with means of closing to permit the control of draught
and smoke.