To exempt combustible fabric vibration isolation connectors between ducts and air outlet units from the requirements of Sentence 3.6.5.2.(1), which would otherwise require the connectors to be noncombustible, if certain conditions are met.
This is to limit the probability that the connectors will contribute to the growth or spread of fire, which could lead to the spread of fire to other parts of the building by means of the air duct systems, which could lead to harm to persons.