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IMC Chapter 6 — Duct Systems

Updated Mar 26, 2026
Duct materials, SMACNA construction, fire/smoke dampers, flex duct, plenum requirements.

IMC Ch6: galvanized steel per SMACNA. Round spiral 26ga typical. Flex max 5ft accessible. Fire dampers: 1.5hr at 1hr barriers, 3hr at 2hr. Smoke dampers at smoke barriers. 20x20in min access. Duct insulation R-6 to R-8 supply in unconditioned space. Seal Class A supply, B return.

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IMCductSMACNAfire-dampersmoke-damperflex-duct
DETAILS
code year
2024
code system
IMC
code section
Chapter 6
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