ASTM E84 cannot be used to establish the hourly fire-resistance rating of a structural member or assembly. Therefore, option B is correct.
ASTM E84 evaluates surface-burning characteristics , principally flame-spread and smoke-developed indices. Those measurements characterize how a material ' s exposed surface behaves when subjected to the standard tunnel test. They do not demonstrate that a wall, floor, roof, beam, column, or structural assembly will maintain integrity and structural performance for one, two, or three hours.
Fire-resistance ratings are instead established through the methods recognized by the IBC, including standard fire testing—principally ASTM E119 or UL 263—prescriptive rated construction provided by Section 721, and calculated fire-resistance procedures under Section 722. The code also recognizes appropriately documented approved designs and other approved methods within the Section 703 framework.
This distinction is particularly important in mass timber work because ASTM E84 may appear elsewhere in the code for flame-spread limitations on materials, but an acceptable E84 result does not establish structural fire endurance.
The special inspector must determine which approved fire-resistance methodology applies and verify that the installed assembly precisely reflects that design.
References/Topics: 2021 IBC Sections 703, 721 and 722; ASTM E119; UL 263; distinction between fire resistance and ASTM E84 surface-burning testing.
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