/ Field knowledge · IMC 607.6
A static CRD is not listed for a system that runs during a fire.
A horizontal duct opening is never “just a floor penetration.” Protection is a shaft, a fire damper at the floor line, a ceiling radiation damper (CRD), a tested assembly, or a qualifying exception. A CRD is not a fire damper. A static CRD is not a dynamic CRD. Specifying a static CRD in a system that runs during a fire is a listing violation.
Educational 2024 International Mechanical Code (IMC) 607.6–607.6.3 from Daily Code Talk. Confirm the adopted edition. Distinct from CRD at corridor membranes (607.5.4) and shafts (607.5.5). This is not a damper schedule.
- 607.6: air-duct penetrations through floors, floor/ceiling assemblies, or roof/ceiling membranes — IBC 713 shaft, or 607.6.1 through 607.6.3. Identify which path first.
- 607.6.1 through penetrations: a duct through a rated floor/ceiling connecting not more than two stories may avoid a shaft if a listed fire damper is at the floor line, or the duct is protected as a through-penetration firestop system per IBC 714.5.
- Small-steel-duct exception (not Groups I-2 and I-3): three floors or fewer, no fire damper at each floor — only if every condition is met at once. Cumulative: routed in a wall cavity, minimum 26 gage steel, serving a single dwelling or sleeping unit only, continuous to the exterior, maximum 4 inch diameter, within the code’s area limits, annular space protected. Miss one and it does not apply.
- 607.6.2 membrane penetrations: generally a shaft or a listed CRD. The CRD is only valid as part of the specific tested floor/ceiling or roof/ceiling assembly. Dynamic listing if the system is designed to operate during a fire. Static CRD only where the system is not designed to operate during a fire, unless a listed control closes the system and satisfies the listing’s static condition.
- 607.6.3 nonrated floors still need protection (shaft, noncombustible annular-space protection, or fire dampers) depending on stories connected and construction type. Exception: fire dampers not required in ducts contained entirely within an individual dwelling unit.
On the set: through vs membrane vs nonrated, assembly rating, story count, protection method, and — for every CRD — whether the fan runs during a fire (M-603).
Static CRD, exhaust that stays on in a fire
The damper is not listed for that condition and can fail as tested. Before specifying any CRD, read the fan sequence: does this system operate during a fire event? That single answer drives the listing.
Source: Daily Code Talk — IMC 607.6 · tool: Dynamic vs static CRD · listing: 607.2 · corridors: 607.5.4 · walls: 607.5.1–607.5.2.
What to send
Where the duct crosses a floor or rated ceiling, how many stories it connects, the fan sequence (does it run in a fire?), and any CRD product named.
If the CRD is static and the fan stays on in a fire
Send the sequence and the penetration. Masterbuild will say whether 607.6.2.1 still has a listing miss — or 607.6.1 still has a 4-inch exception missing a condition.
Send Project Background+1 (786) 398-6940 · osmany.portal@masterbuildconsulting.com
Masterbuild provides engineering services under a written scope. Nothing on this page is project-specific engineering advice, a code interpretation for your project, or a representation about permit approval. Confirm the adopted edition. The 26 gage / 4 inch exception, two-story through-penetration path, and dynamic vs static CRD split are 2024 IMC 607.6 education from Daily Code Talk — not a damper schedule. This page is not legal advice.