To exempt wall and ceiling finishes in exterior exit passageways from the requirements of Sentence 9.10.17.1.(1), which would otherwise limit surface flame-spread rating to 150, and require a lower maximum flame-spread rating on at least 90% of the surface areas, on the basis that the lower rating is needed in these locations to protect persons during evacuation.
To limit the probability that certain finishes having an inappropriately high flame-spread property will be used in certain passageways that provide means of egress, which could lead to the spread of fire across the exposed surfaces of the finishes, which could lead to delays in the evacuation or movement of persons to a safe place, which could lead to harm to persons.