Equivalent Thickness. Testing every possible wall combination is

not feasible. The equivalent thickness method accurately predicts

fire resistance.

Part 1 of this guide describes ASTM E-119 testing, which is one way that building components such as walls, partitions

and floor/ceiling assemblies qualify for fire ratings. When an assembly passes such a test, which usually is conducted at an

independent testing lab such as Underwriters Laboratories, Inc., that specific combination of products assembled exactly as

tested receives a UL Classification number that can be used to designate it in project specifications.

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