Where flashing is installed between a shingle roof and a chimney, to limit the probability of an inappropriate flashing configuration, which could lead to water spreading horizontally as it descends the roof slope and flowing beyond the area protected by the horizontal leg of flashing, which could lead to precipitation or meltwater ingress into chimneys, which could lead to damage to chimney liners from freeze-thaw stresses, which could lead to the escape of heat or flames, which could lead to the ignition of combustible building components, which could lead to harm to persons [see analysis for Sentence 9.21.4.6.(1)].