1 The required protection of stairways penetrating more than a single deck can be achieved by:
.1 a stairway enclosure allowing access from one stair to a superimposed stair within such enclosure, the entrances to which should consist self-closing "A" class fire doors at each deck level (see figure 1 of regulation 46.1 in the appendix); or
.2 a stairway enclosure enclosing the stairs only, in combination with self-closing "A"class fire doors at each deck level and at each end of a stair. No requirements apply to the stairs except that they should be of steel frame structure or be made of equivalent material (see figure 2.1 of regulation 46.1 in the appendix); or
.3 a stairway enclosure enclosing the stairs only, in combination with fully closed steel stairs, going from steel wall to steel wall and "A" class fire doors fitted at one end of each stair (see figure 2.2 of regulation 46.1 in the appendix).
2 Dumb-waiters are to be regarded as lifts.
The "A-O" requirements of paragraph 1 of regulation II-2/46 may be reduced to "B-O".