3.6.4.3.(1)

Objective

OS1 Fire Safety

Attribution

Intent

Intent 1:

To supersede the requirements of Sentence 3.1.5.15.(1), which would otherwise permit combustible ducts used in horizontal runs without any other restrictions, and to supersede the requirements of Article 3.6.5.1., which would otherwise require noncombustible materials, and permit combustible materials if certain conditions are met.

This is to limit the probability that:

  • combustible material having inappropriately high flame spread and smoke development properties will be used in concealed spaces used as plenums, which could lead to the development of an inappropriate amount of smoke and the spread of fire across the exposed surfaces of the material, which could lead to the spread of fire and smoke from one fire compartment to another fire compartment by means of the plenum, which could lead to harm to persons in the other fire compartment, and
  • supports for the ceiling membrane will prematurely fail when exposed to fire conditions, which could lead to the spread of fire into the floor or roof assembly, and to other parts of the building, which could lead to harm to persons in the other parts of the building.

Intent 2:

To supersede the requirements of Sentence 9.33.6.2.(1), which would otherwise require ducts, duct connectors, associated fittings and plenums used in air duct systems to be constructed of noncombustible material.

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