§ 149. Public halls. 1. Every public hall shall be everywhere at least three feet in clear width.

2. Every public hall shall be completely enclosed with fireproof floor, ceiling and walls, and, in dwellings erected under plans filed in the department after September first, nineteen hundred fifty-one, such hall shall be separated from every stair by fireproof partitions or walls. All doors and their assemblies opening from such hall or stairs shall be fireproof, with the doors self-closing and without transoms, except that in a dwelling three stories or less in height occupied by not more than four families on each story, or in a class A dwelling or any section thereof two stories or less in height, any such hall which furnishes access to only one stair need not be separated from such stair by any partition or door and the walls of a public hall may be fire-retarded and the floors may be provided with three inches or more of incombustible deafening materials between the beams instead of being fireproof.

3. Except in dwellings three stories or less in height and occupied by two families or less on every story, and except as provided in subdivisions four to seven inclusive, every public hall shall have at least one window opening directly upon a street or upon a lawful yard or court. There shall be such a window at the end of each such hall and at right angles to its length, with an additional window in each forty feet of hall or fraction thereof beyond the first sixty feet from such end window; or the hall shall have one window opening directly upon a street or upon a lawful yard or court in every forty feet of its length or fraction thereof measured from one end of the hall.

4. When the length of any recess or return off a public hall does not exceed twice the width of such recess or return, no window shall be required therein. But whenever the length of a recess or return exceeds twice its width, there shall be an additional window or windows meeting the requirements for a separate public hall. No entrance hall shall have a return or recess which exceeds in length twice its width.

5. The foregoing provisions of this section with regard to lighting and ventilation shall not apply to a vestibule or other public hall which serves as a means of access from one or more apartments opening thereon to a fire-stair or fire-tower meeting the requirements of section one hundred forty-four if such vestibule or public hall is lighted and ventilated as required for fireproof dwellings by sections thirty-seven and one hundred seven.

6. The foregoing provisions of this section with regard to lighting and ventilation shall not apply to that portion of an entrance hall between the first flight of stairs and the entrance provided the entrance door contains five square feet or more of glazed surface or such entrance hall does not extend from the outer entrance of the dwelling more than sixty feet.

7. A passenger elevator vestibule not exceeding in length twice the parallel length of the elevator shaft or shafts opening into it need not be equipped with a window if it conforms to the requirements of sections thirty-seven and one hundred seven for public halls in fireproof multiple dwellings. Every door and its assembly separating such a vestibule from any public hall connected with a stair, fire-stair or fire-tower shall be fireproof, with the door self-closing and glazed with good quality wire glass ten square feet or more in area. No such door shall be kept open by any device whatever.

8. Any part of a public hall that is shut off from any other part of such hall by a door or doors shall be deemed a separate hall.