The test involves construction

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Test procedure
The NFPA 285 test evaluates flame spread—vertically and horizontally—across the wall assembly, along with ensuring temperatures are not exceeded within specific areas.

of a two-story room, with the proposed wall assembly as the exterior wall. The lower room includes a window opening (non-glazed). To simulate a building fire, 
a gas burner is placed in the center of the lower room, and a second, portable gas burner is placed in the window opening. The two burners are ignited at specified intervals during the 30-minute test and must heat rcs data the first floor to defined temperatures by specified times.

Test results
The test results are expressed as either ‘pass’ or ‘fail.’ Either an insulation (or other product) is deemed to be NFPA 285-compliant in a given wall assembly, or it is not. NFPA 285 does not rate using degrees of performance, as is the case with some fire tests (such as those for fire-rated glazing that result in 30-, 60-, or 90-minute ratings.