Every stairway within accommodation spaces, service spaces and control stations shall be constructed of steel except where the Secretary of State may approve the use of other equivalent material. Every such stairway and lift shall lie respectively within an enclosure or trunk constructed of “A” Class divisions of “A-O” standard except that an isolated stairway serving only two decks shall only be required to be enclosed at one level by either “A” Class divisions of “A-O” standard or “B” Class divisions of “B-O” standard provided that the fire integrity of any bulkhead which separates a stairway from either a machinery space of Category A or a cargo pump room shall be determined by reference to Table 3 of Schedule 2 in Merchant Shipping Notice MSN 1668.

Every opening in a stairway enclosure and lift trunk shall be provided with a means of closure which shall be permanently attached thereto and which shall comply with the requirements of regulation 93 or 94, whichever is applicable.