IMC 607.5.5 through 607.5.7 covers shafts, rated exterior walls, and smoke partitions. Shaft penetrations are easy to oversimplify - sometimes dampers are required, sometimes they are prohibited, and sometimes the exception depends on upward airflow, steel subduct geometry, smoke control, or garage shaft separation.
Plain English: Plain-English Highlights
607.5.5 Shaft Enclosures
Ducts and air transfer openings through shaft enclosures generally require listed fire and smoke damper(s) installed per their listing.
607.5.5 Shaft Exceptions
FD(s) may be omitted for certain steel exhaust subducts where the subduct extends at least 22 inches vertically and a continuously powered fan maintains upward exhaust. Both conditions are required simultaneously.
FD(s) may also be omitted where the penetration is tested as part of the rated assembly, where smoke control would be impaired, or at certain separated garage shafts.
In certain Group B and R sprinklered buildings, smoke dampers may be omitted for kitchen, dryer, bathroom, and toilet exhaust openings using compliant steel subducts with continuous upward exhaust.
FD and combination FD/SD are not required - and are specifically prohibited - in kitchen and dryer exhaust systems where dampers are prohibited by code.
607.5.5.1 Continuous Upward Flow
FD/SD cannot be installed where closure would stop required continuous upward airflow. When continuous upward flow is required, alternative shaft protection must be used.
607.5.5.2 Enclosure at the Bottom
Shafts that do not extend to the bottom of the building must be protected per IBC 713.11.
607.5.6 Exterior Walls
Ducts and air transfer openings in rated exterior walls requiring protected openings under IBC 705.12 need listed fire dampers.
607.5.7 Smoke Partitions
Air transfer openings through smoke partitions require listed smoke dampers.
Exception: where a SD would interfere with required smoke control, approved alternative protection is required. The exception does not allow unprotected openings.
On Plans: Why it matters
Shaft penetrations are easy to oversimplify. Sometimes dampers are required. Sometimes they are prohibited. Sometimes the exception depends on upward airflow, steel subduct geometry, smoke control, or garage shaft separation. A fire damper in a grease exhaust shaft is not a conservative choice - it is a prohibited condition that increases fire risk.
Code Path: Where to show it - M-001: IMC 607.5.5-607.5.7 notes and exception basis - M-101: openings at shafts, exterior walls, and smoke partitions with shaft type labeled - M-501: shaft penetration, subduct height, damper, sleeve, and access details - M-603: smoke control sequence and continuous exhaust fan operation basis - A / LS sheets: shaft ratings, exterior wall ratings, smoke partitions, and garage separation
Check: Do - Show subduct height, material, fan operation, and airflow direction when using the subduct exception - Label the shaft type on M-101 before selecting the damper type - Coordinate damper omissions with code prohibitions and smoke control logic - Show bottom-of-shaft protection for partial-height shafts
Review Risk: Don't - Don't place dampers where code prohibits them - kitchen grease and dryer exhaust systems are prohibited-damper conditions - Don't omit shaft dampers without showing the exception basis - Don't ignore continuous fan operation when relying on the upward airflow exception
Field Tip: Field tip For shaft penetrations, ask: is this a supply shaft, exhaust shaft, smoke control shaft, garage shaft, or prohibited-damper system? That answer drives the damper, exception, or alternate protection. If you can't answer the shaft type from the drawings, the damper selection can't be verified.
Masterbuild QA Lens
The prohibited-damper condition is the most dangerous coordination error in 607.5.5. A fire damper in a grease exhaust shaft creates a grease accumulation point that increases fire risk. Confirm the shaft system type before specifying any damper. If the system is kitchen exhaust, the question is not 'which damper type' but 'this system cannot have a damper - what is the required alternative?'
Drawing / Submittal Check
For each shaft penetration: (1) label the shaft type on M-101; (2) for FD/SD exceptions: show subduct height (min 22 in), steel specification, and fan operation basis; (3) for prohibited-damper shafts: note the prohibiting IMC section and the alternative protection method; (4) for partial-height shafts: show bottom protection per IBC 713.11; (5) for smoke partitions: confirm SD actuation and smoke control coordination on M-603.
Common Review Risk
Three patterns: (1) subduct exception applied without showing subduct height, steel gauge, and fan operation; (2) fire damper shown in a grease exhaust or dryer exhaust shaft - both prohibited; (3) partial-height shaft without bottom protection. Each is a first-cycle comment.
When To Escalate
Escalate when a shaft serves multiple exhaust system types (requiring shaft separation coordination), when smoke control requires shafts to remain open during operation, or when the IBC 406.5 parking garage exception involves a configuration requiring PE verification.
Rated Assembly Coordination
Shaft enclosures are fire-resistance-rated assemblies. The shaft rating, duct material, damper or alternative protection, access, and smoke control coordination are a single compliance package. Missing any element is a plan review flag. Run the shaft penetration checklist as a coordinated review across M-101, M-501, M-603, and the architectural life-safety plan.