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Combustible Materials for Use in Air-Handling Spaces (Plenums)

Fire test under UL Observation

In building construction, the space between the top of the finished ceiling and the underside of the floor or roof is called a plenum. This area is permitted to supply air to, or return air from, occupied spaces. For these air-handling spaces, all materials are required to be noncombustible or limited combustible with a maximum smoke index of 50 (based on UL 723, ASTM E84 or NFPA 255). Exceptions are permitted for combustible electrical equipment or other discrete combustible products that have a peak heat release rate not greater than 100 kW, a peak optical density not greater than 0.5 and an average optical density not greater than 0.15 when tested in accordance with UL 2043.

Test Standards

  • UL 2043 -- Fire Test for Heat and Visible Smoke Release for Discrete Product and their Accessories Installed in Air-Handling Spaces

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