1. Except as provided in paragraph g of subdivision three of section one hundred seventy-one, egress from every apartment on each story shall be provided as follows:
a. If a dwelling is two stories or less in height, or if it is three stories including a basement in height and conforms to the conditions of subdivision four of section one hundred seventy-seven, a single means of egress from each story to the street shall be sufficient.
b. Every other dwelling shall have either two independent means of egress or one means of egress equipped with a sprinkler system.
c. At least one means of egress shall be a stair extending to and through the roof by a bulkhead, except that a scuttle may be used in lieu of a bulkhead if the dwelling does not exceed a basement and three other stories in height, or if it does not exceed a basement and four other stories in height and is occupied by not more than two families on any story, and except that no bulkhead or scuttle, or stair or ladder leading thereto, shall be required where the roof is a peak roof with a pitch of more than fifteen degrees.
d. Whenever a second means of egress is required, it shall, except as provided in paragraph f, extend from the entrance story to the roof, and shall be located eight feet or more from the first means of egress unless separated therefrom by a public hall or elevator vestibule. Such second means of egress shall be directly accessible at each story to each apartment without having to pass through the first means of egress.
e. A required second means of egress shall be either a system of outside fire-escapes, constructed and arranged as provided in section fifty-three for fire-escapes erected after April eighteenth, nineteen hundred twenty-nine, a fire-stair, a fire-tower or a connection with an adjoining dwelling as provided in paragraph f below.
f. If the department upon the application of the owner shall deem it feasible and so permit, the owner shall provide, and at all times maintain unobstructed, a first means of egress extending by means of a stair from the street through a bulkhead to the roof and thence from the roof of such dwelling to the roof of an adjoining dwelling and through such adjoining dwelling to the street and a second means of egress from each apartment to a room on the same story or level in an adjoining dwelling by means of a balcony. Every such balcony shall comply with the requirements for a fire-escape balcony, except that its minimum clear width shall be two feet instead of three feet. If at any time such access to the street shall in the opinion of the department be obstructed or be otherwise unsafe the department shall revoke the permit, and upon such revocation the owner shall provide one of the other types of egress permitted in this section.
g. When the department shall find it impractical to erect an independent fire-escape and shall refuse to permit egress by means of balconies to an adjoining dwelling, the department may permit the erection or use of a fire-escape to which the occupants of such dwelling have safe, unobstructed access in common with the occupants of an adjoining dwelling.
h. Where a required means of egress leads to a yard less than thirty feet in depth, except as provided in paragraph f of subdivision four of section one hundred seventy-seven, there shall be access from such yard to the street through a court or fireproof passage, or to the yard or court of adjoining premises by a gate or door through an intervening fence, or, if the department deems such gate or door impracticable and so certifies, by a ladder to the top of an intervening fence or wall or by such other means as the department may require.
2. Where a sprinkler system is required such system shall be equipped on each story with one or more automatic sprinkler heads with fusible struts which shall be constructed to fuse at a temperature not higher than one hundred sixty-five degrees Fahrenheit and all of which shall be constructed, located and arranged in every stair and entrance hall, and in every closet opening therefrom, in such manner as the department may require. Such system may be attached to the city water supply main if the normal minimum pressure thereon, measured in pounds per square inch at the street level at the point of connection with said main, is not less than the number of stories in the height of the dwelling, multiplied by five, plus fifteen. If such normal minimum pressure is less than the required amount or such system is not attached to the city water supply main, it shall be supplied with water from a tank located on the roof of the dwelling of such capacity and construction as the department may deem necessary. Such sprinkler system shall be maintained continuously in good repair and serviceable condition.