To exempt public corridor separations from the application of Sentence 9.10.9.15.(1) by waiving the requirement for a minimum 45 min fire-resistance rating, if certain conditions are met [i.e. smoke-tight barrier of not less than 12.7 mm gypsum board is installed on both sides of walls and on the underside of floor-ceiling framing separating the corridor from the remainder of the building], on the basis that construction of rated fire separations may be cost-prohibitive and the reduction in protection from spread of fire is offset by more stringent requirements for notification of occupants.
To limit the probability that fire or smoke will spread into a public corridor, or from a public corridor into the remainder of the building, which could lead to damage to the building.