What does the NFPA 90A code say about using combustible materials in a return air plenum?

NFPA 90A enforces a strict life-safety standard: any materials exposed inside a ceiling return air plenum space (including insulation jackets, pipe hangers, sealants, and wiring covers) must possess a maximum Flame Spread Index of 25 and a maximum Smoke Developed Index of 50 when tested under ASTM E84 standards. Standard residential-grade plastics, vinyl tapes, and unrated foams are explicitly prohibited inside commercial air streams.

[' NFPA 90A enforces a strict life-safety standard: any materials exposed inside a ceiling return air plenum space (including insulation jackets, pipe hangers, sealants, and wiring covers) must possess a maximum Flame Spread Index of 25 and a maximum Smoke Developed Index of 50 when tested under ASTM E84 standards. Standard residential-grade plastics, vinyl tapes, and unrated foams are explicitly prohibited inside commercial air streams.']

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NFPA 90A enforces a strict life-safety standard: any materials exposed inside a ceiling return air plenum space (including insulation jackets, pipe hangers, sealants, and wiring...

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what does the nfpa 90a code say about using combustible materials in a return air plenum?

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