To limit the probability that heat radiating from the fireplace opening to a hearth that rests directly on a combustible floor will raise the hearth temperature excessively, which could lead to the ignition of combustible building components, which could lead to damage to the building.
To exempt certain fireplaces from the application of Sentence 9.22.5.2.(1), where the fireplace opening is raised sufficiently above a combustible floor to reduce the risk of raising the hearth temperature excessively.