To exempt certain ceilings 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 exposed ceiling surface, on the basis that the lower flame-spread rating is needed in these locations [exits or public corridors that are a part of a means of egress] to protect persons during evacuation.
To limit the probability that certain finishes having an inappropriately high flame-spread property will be used in exits or public corridors that are a part of a 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.