IMC 607.5 is where the reviewer matches the rated assembly type to the correct damper, exception, and listing. A duct crossing a rated wall may need a fire damper, a smoke damper, a combination FD/SD, or both — the answer depends on which assembly type is being crossed.
607.5 Where Required: Fire dampers (FD), smoke dampers (SD), combination fire/smoke dampers (FD/SD), ceiling radiation dampers (CRD), and corridor dampers are required at the locations listed in 607.5.1 through 607.5.7. Where an assembly requires both fire and smoke protection, a combination FD/SD or both an FD and SD must be provided.
607.5.1 Fire Walls: Ducts and air transfer openings permitted through fire walls by IBC 706.11 must be protected with listed FDs installed per their listing. Fire walls are the most restrictive vertical assembly — penetrations are limited and require a permitted opening under IBC 706.11.
607.5.1.1 Horizontal Exits: Where a fire wall serves as a horizontal exit, each duct or air transfer opening also requires a listed SD. The FD alone is not sufficient at a horizontal exit.
607.5.2 Fire Barriers: Ducts and air transfer openings through fire barriers generally require a listed FD. Ducts and air transfer openings cannot penetrate interior exit stairways, ramps, or exit passageways except where permitted by IBC 1023.5 and 1024.6.
607.5.2 Exceptions: FDs are not required at certain fire barrier penetrations where: (1) the penetration is tested as part of the rated assembly; (2) smoke control would be impaired; or (3) the fully ducted HVAC exception is met. The fully ducted exception applies only to 1-hour-or-less fire barriers, non-Group H areas, sprinklered buildings, and continuous minimum 26-gage sheet steel duct from equipment to terminals. All four conditions must be met simultaneously.
607.5.2.1 Horizontal Exits: Where a fire barrier serves as a horizontal exit, each duct or air transfer opening also requires a listed SD — same requirement as fire walls.
Key Distinction: Fire walls and fire barriers are not interchangeable. Fire walls must be able to stand independently after fire destroys either adjacent section. Fire barriers separate areas within a building. The damper exception that applies to a fire barrier does not apply to a fire wall.
Why it matters: Applying a fire barrier exception to a fire wall penetration is a code error — not a conservative choice. The most common plan review comment on 607.5 work: damper type selected without identifying the assembly type. The assembly must be labeled on the mechanical plan before the damper schedule is finalized.
Where to show it: M-001 — IMC 607.5 damper notes and exception criteria. M-101 — duct and transfer openings at fire walls, fire barriers, and horizontal exits. M-501 — damper, sleeve, access, and penetration details with UL design number. M-603 — damper actuation and smoke control coordination. A/LS sheets — rated assembly labels coordinated with mechanical plan.
Do: Identify the rated assembly type before selecting the damper. Show whether FD, SD, or FD/SD is required at each penetration. Coordinate horizontal exits carefully — they require SD at both fire walls and fire barriers. For the fully ducted exception, document all four conditions on M-001.
Don’t: Don’t treat fire walls and fire barriers the same — different structural roles, different damper rules. Don’t omit SD at horizontal exits where required. Don’t apply the fully ducted exception without confirming duct gauge, occupancy, sprinkler status, and barrier rating.
Field Tip: Before applying any exception, ask: what wall is this, what is its rating, does it serve as a horizontal exit, and is the duct continuous and fully ducted? If the drawings don’t answer all questions, the exception basis is not established.
Masterbuild QA Lens
IMC 607 damper requirements are triggered by the rated assembly type, not by the duct system. Confirm the assembly label from the architectural drawings before the damper schedule is finalized.
Drawing / Submittal Check
For every duct and transfer opening at a rated assembly: assembly type on M plan, damper type with listing, access location, sleeve and retaining angle details, exception basis on M-001 if applicable.
Common Review Risk
Damper type selected without identifying the assembly type. Exception applied without documenting all conditions. Access panel missing or not coordinated with ceiling or shaft construction.
When To Escalate
Escalate when the rated assembly type cannot be confirmed from architectural drawings, when smoke control and damper requirements conflict, or when the exception conditions cannot be established from the project documents.
Rated Assembly Coordination
The mechanical plan must match the architectural life-safety plan. Assembly labels, damper types, and exception bases must agree between the M drawings and the A/LS drawings. Disagreements discovered at permit review become correction comments.