§ 28. Stairs and entrance halls. In every such dwelling three stories or more in height the wood wainscoting and other combustible materials on the wall and ceiling surfaces in all halls shall be removed and replaced with incombustible or other fire-resistive materials. In lieu of such removal, a sprinkler system may be installed in such halls or such wainscoting and the combustible surfaces may be treated or covered in a manner satisfactory to the department with a surface fire-retardant approved by the department. In such a dwelling, however, any entrance door and every door opening into any entrance hall, stair hall, or other public hall connected therewith, shall be self-closing. Every interior sash, or opening other than a door, in the walls or partitions of such halls and every window therein not opening to the outer air shall be sealed with fire-resistive materials.