To limit the probability that fire in a vertical service space will ignite foamed plastic insulation lining the service space, which could lead to the spread of fire to other parts of the building, which could lead to harm to persons.
To expand the application of Article 3.1.5.12. [more specifically Sentence 3.1.5.12.(2)], which would otherwise apply only to buildings described in Sentence 1.3.3.2.(1) of Division A that are required to be of noncombustible construction.