/ Field knowledge · IMC 607.7
Flex does not cross the rated line.
Classify the listed product before drawing a crossing. Under 2024 IMC 603.6.2.2, a flexible air connector cannot pass through any wall, floor or ceiling, even an unrated one. Section 607.7 separately prohibits flexible ducts and connectors through fire-resistance-rated assemblies. A smoke designation needs its own assembly-rating and damper review.
Educational 2024 IMC 603.6.2.2 and 607.7. Confirm the adopted edition, the product listing, and the architectural life-safety plan. This is not a damper selection. Read the connector rule and rated-assembly rule. Packet: English PDF · PDF en español.
- Record whether the UL 181 listed item is a flexible air duct or flexible air connector; they have different installation limits.
- Connector, 603.6.2.2: it shall not pass through any wall, floor or ceiling. A zero-hour or unrated partition does not remove this connector prohibition.
- Duct or connector, 607.7: neither may pass through any fire-resistance-rated assembly. A short run or a proposed damper does not create a flex-penetration exception.
- Identify smoke barrier versus smoke partition and the actual fire-resistance rating from the life-safety set. A smoke designation alone is not the 607.7 rating test; smoke damper, air-transfer-opening, and penetration requirements still need their separate review.
- Where an eligible rigid duct crosses, detail its listed material and applicable damper, sleeve, firestop or shaft protection for that exact assembly under 607.5-607.6.
A connector through an unrated corridor wall
That is prohibited by 603.6.2.2 even if the wall has no fire-resistance rating. Overlay the life-safety plan on the mechanical set, distinguish duct from connector, and move the transition before the boundary.
Source: 2024 IMC Chapter 6 · DCT 607.7 · tool: flex screen · dispersion: 603.17 · outlets: 603.18 · dampers: 607 · construction: 603.
What to send
The reflected ceiling plan, UL 181 product classification, architectural wall/floor/ceiling and smoke designations, and proposed flex-to-rigid transition and penetration details.
If a flex run reaches a boundary
Send the product label and boundary detail. MasterBuild can scope the connector prohibition, rated-assembly condition and separate damper review.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
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