Exit passageways shall be maintained free of obstructions at all times. Not more than fifty percent of the total number of vertical exits provided for a building may be served by a single exit passageway, except as provided in subdivision (h) of section 27-370 of this article.
(a) Capacity. The capacity of exit passageways shall be as listed in table 6-1.
(b) Width. The width of an exit passageway serving one vertical exit shall be equal to the width of the vertical exit. The width of an exit passageway serving two or more vertical exits shall be equal to seventy-five percent of the width of all of the vertical exits that it serves. Width shall be measured in the clear between the narrowest points at any projections such as radiators, door swings, or pilasters.
(c) Height. Exit passageways shall have a clear height of seven feet six inches for at least seventy-five per cent of the floor area, with no point less than seven feet in height. No projection below the ceiling shall be located so as to obstruct full view of exit signs.
(e) Construction. The construction of exit passageways shall be as required by table 3-4 for the applicable construction class of the building.
(f) Openings. No openings other than exit doors shall be permitted in exit passageways, except as provided in subdivision (h) of this section.
(g) Interior finish. The interior finish of exit passageways shall be in accordance with the requirements of table 5-4.
(h) Street floor lobbies. Street floor lobbies may be used as exit passageways when they comply with the requirements of subdivisions (a) through (g) of this section subject to the following modifications:
(1) VERTICAL EXITS SERVED. One hundred per cent of the total number of vertical exits provided for a building may be served by a street floor lobby, if egress is provided in two different directions from the discharge points of all vertical exits to open exterior spaces that are remote from each other.
(2) WIDTH. Street floor lobbies serving as exit passageways shall be increased in width to accommodate the occupant load of all communicating spaces on the lobby floor that exit through them. The capacity per unit of width shall be as listed in table 6-1.
(3) OPENINGS. Openings between street floor lobbies serving as exit passageways and elevators or communicating spaces shall comply with the following:
a. Doors.
1. Doors to stairways and elevators, and unsprinklered communicating spaces classified in occupancy group B-2, D-2, F-1 or F-2 shall be self-closing fire doors having a one and one-half hour fire protection rating.
2. Doors to unsprinklered communicating spaces classified in occupancy group G, H or J, or sprinklered communicating spaces classified in occupancy group B-2, D-2, F-1 or F-2 may be either:
(a) self-closing fire doors having a three-quarter hour fire protection rating, or
(b) glass or other noncombustible doors installed in conjunction with automatic fire doors having a one and one-half hour fire protection rating, with sprinkler heads installed over the doors on the room side.
3. No other door openings shall be authorized except as otherwise provided in this section.
b. Other openings. Other openings to spaces classified in occupancy group C, E, F, G, H or J shall be permitted, provided they have a maximum length of eight feet and a maximum height of eight feet, are glazed by one-quarter inch polished plate glass or equivalent and are protected by automatic fire doors having a one and one-half hour fire protection rating and by automatic sprinklers complying with the construction requirements of subchapter seventeen of this chapter over the openings on the room side.
c. Separations and limitations. Openings permitted by subparagraphs a and b of this paragraph shall not exceed in total length fifty per cent of the length of such enclosure wall except where the length of such wall is less than sixteen feet. Adjoining openings shall be separated from each other a minimum of three feet by construction having a two hour fire-resistance rating.
d. Notwithstanding the restrictions in subparagraphs a, b, and c of this paragraph, the following openings may be authorized:
1. A space classified in occupancy group C, E, F-3 or, F-4 within fire separations having a minimum fire-resistance rating of one hour, with an area not exceeding twenty-five hundred square feet, may have an unlimited length of show window under the following conditions:
(a) The maximum depth of show window shall be three feet.
(b) Automatic sprinklers complying with the construction requirements of subchapter seventeen of this chapter, shall be provided in the show window display area.
(c) The show window display area shall be protected on all sides, except for the glazed window, by construction having a two hour fire-resistance rating with access provided by means of a fireproof self-closing door having a three-quarter hour fire protection rating.
(d) The show window shall be glazed by one-quarter inch polished plate glass or equivalent.
(e) Glass or other noncombustible doors may be used for entrance to or egress from the space within fire separations when installed in combination with automatic fire doors having a one and one-half hour fire protection rating. Such automatic fire doors shall be located on the room side and shall be held open by approved door-holding devices actuated to release automatically upon the activation of smoke detecting devices, whether of the photoelectric cell or other approved type. In addition, automatic sprinkler heads, complying with the construction requirements of subchapter seventeen of this chapter, shall be provided over the door openings on the room side.
2. A space classified in occupancy group C, E, F-3, or F-4 within fire separations having a minimum fire-resistance rating of one hour, with an area not exceeding three thousand square feet, may have a maximum total length of unprotected openings upon a corridor or exit passageway not exceeding fifty percent of the space frontage along such corridor or exit passageway under the following conditions:
(a) The entire space shall be provided with automatic sprinklers complying with the construction requirements of subchapter seventeen of this chapter.
(b) The show window shall be glazed by one-quarter inch polished plate glass or equivalent.
(c) All corridor or exit passageway doors shall be self-closing, noncombustible, and smokeproof.
3. Show windows or other openings of unlimited lengths and heights shall be permitted on any corridor or exit passageway without requirements for fire-resistance doors under the following conditions:
(a) The entire floor area, including the corridors or exit passageways, shall be provided with automatic sprinklers complying with the construction requirements of subchapter seventeen of this chapter.
(b) The occupancy of all spaces on the floor shall be limited to occupancy groups C, E, F-3 and F-4.
(c) The widths of the corridors or passageways shall exceed the requirements of table 6-1 or subdivision (b) of this section, whichever is applicable, by at least fifty percent.
(d) All doors opening on the corridors or exit passageways shall be smokeproof, noncombustible self-closing doors.
(e) Show windows or other openings shall be glazed by one-quarter inch polished plate glass or equivalent.
(f) Each corridor or exit passageway shall be provided with a fresh air intake, a positive smoke exhaust system and smoke detectors which, when activated, shall permit circulation only of fresh air.
(4) OCCUPANCY. Street floor lobbies serving as exit passageways may be occupied by newsstands, candy and tobacco stands, information booths or similar occupancies, if such stands or booths are constructed of noncombustible materials, or of materials which comply with the requirements of section 27-348 of article five of subchapter five of this chapter for interior finish for exit passageways, provided that such stands or booths:
a. do not occupy more than one hundred square feet or five percent of the net floor area of the lobby, whichever is greater; and
b. do not reduce the required clear width of the lobby at any point; and
c. if constructed of combustible materials are protected by no less than two automatic sprinkler heads. Water for such sprinkler heads may be supplied from the domestic water supply system.