3.2.8.4.Vestibules

(1) An exit opening into an interconnected floor space shall be protected at each opening into the interconnected floor space by a vestibule (a) with doorways that are not less than 1.8 m apart, (b) that is separated from the remainder of the floor area by a fire separation that is not required to have a fire- resistance rating, and (See Note A-3.1.8.1.(1)(b)) (c) that is designed to limit the passage of smoke so that the exit stair shaft does not contain more than 1% by volume of contaminated air from the fire floor, assuming an outdoor temperature equal to the January design temperature on a 2.5% basis determined in accordance with MMAH Supplementary Standard SB-1, “Climatic and Seismic Data.” (See Note A-3.2.8.4.(1)(c)) (2) An exit opening into an interconnected floor space shall conform to Sentence 3.4.3.2.(6). (3) If an elevator hoistway opens into an interconnected floor space and into storeys above the interconnected floor space, either the elevator doors opening into the interconnected floor space or the elevator doors opening into the storeys above the interconnected floor space shall be protected by vestibules conforming to Sentence (1).