IBC 717.5.4.1
Corridor dampers and other dampers in rated corridors (IBC 717.5.4.1)
Rated corridor walls are fire partitions, so the fire partition rules apply to ducts through them. On top of that, the corridor rules can add a smoke damper, a corridor damper or a ceiling radiation damper.
What counts as a rated corridor: The walls or ceiling of a corridor that the code requires to be fire-resistance rated.
Rules last reviewed October 12, 2026. How the rules are checked
Check your case in the tool (2024 IBC)Start the tool with the 2021 IBC · Start the tool with the 2018 IBC
When each damper is required
Every result the tool can give for a duct carrying heating, cooling or ventilation air, or an air transfer opening, through this assembly. Labels show where a result applies only to ducts, only to air transfer openings, or only in some editions.
Fire damper
- Required
In Group H, none of the 717.5.4 exceptions apply, so ducts and air transfer openings through a fire partition need a listed fire damper.
IBC 717.5.4
- Required
Ducts and air transfer openings through a fire partition need a listed fire damper, and none of the exceptions apply.
IBC 717.5.4
- Not requiredDucts only
In a fully sprinklered building, a duct through a corridor wall that is protected as a through-penetration does not need a fire damper.
IBC 717.5.4 Exc. 1, IBC 714
- Not requiredDucts only
The fire partition is rated 1 hour or less, the building is fully sprinklered, and the duct is a ducted steel HVAC system that is continuous from the equipment to the outlets.
IBC 717.5.4 Exc. 4
- Not requiredDucts only
The duct is a small steel duct above the ceiling with the required steel sleeve detail.
IBC 717.5.4 Exc. 3
Smoke damper
- Required
The corridor requires smoke- and draft-control doors, so a listed smoke damper is required at each duct or air transfer opening through the corridor enclosure.
IBC 717.5.4.1 item 3, IBC 716.2.2.1
- Not required
This corridor is not required to have smoke- and draft-control doors (Group I-2 corridor or multitheater exception).
IBC 716.2.2.1, IBC 717.5.4.1 item 3
- Not required
The building has an approved smoke control system throughout that does not need smoke dampers here.
IBC 717.5.4.1 Exc. 1
- Not requiredDucts only
The duct is steel at least 0.019 inch thick and has no openings serving the corridor.
IBC 717.5.4.1 Exc. 2
Corridor damper
- Required
The corridor ceiling is built like the corridor walls (IBC 708.4 Exception 3), so a corridor damper is required where the duct passes through it. Corridor dampers are tested for both fire and smoke.
IBC 717.5.4.1 item 1, IBC 717.3.1 item 5
Ceiling radiation damper
Two routes lead here. Where the corridor walls stop at the ceiling of a rated floor or roof above (IBC 708.4 Exception 2), IBC 717.5.4.1 item 2 calls for a ceiling radiation damper. Where the corridor walls continue past the ceiling and that ceiling is the lower membrane of a rated floor/ceiling or roof/ceiling assembly, the ceiling penetration rules of IBC 717.6.2 apply instead, with their exceptions.
- Required
The corridor walls stop at the ceiling of a rated floor or roof assembly (IBC 708.4 Exception 2), so a ceiling radiation damper is required where the duct passes through that ceiling.
IBC 717.5.4.1 item 2
- RequiredDucts only
Where a duct passes through the ceiling of the rated assembly, a listed ceiling radiation damper is required at the ceiling line.
Or enclose the duct in a shaft that complies with IBC 713.
IBC 717.6.2 item 2
- RequiredAir transfer openings only
A listed ceiling radiation damper is required at the ceiling line where an opening with no duct attached, such as a diffuser or grille, penetrates the ceiling of the rated assembly.
IBC 717.6.2, IBC 717.6.2 item 3
- Building official approval needed
The code assigns the ceiling radiation damper to the ceiling of a rated floor/ceiling or roof/ceiling assembly (IBC 717.5.4.1 item 2). Here the corridor walls stop at the ceiling under IBC 708.4 Exception 2.2 (sprinklers throughout, including the space between the top of the wall and the floor or roof above, and a corridor ceiling membrane equivalent to the corridor wall membrane) and the floor above is not rated, so the code names no damper for this ceiling. A ceiling radiation damper is the cautious choice; confirm the protection with the building official.
IBC 717.5.4.1 item 2, IBC 708.4 Exc. 2.2
- Not required
The rated assembly was tested and shown not to need ceiling radiation dampers.
IBC 717.6.2 Exc. 1
- Not requiredDucts only
The exhaust or outdoor air duct is inside a wall cavity, protected as required by IBC 714.5.2, and does not run through any other dwelling unit or tenant space.
IBC 717.6.2 Exc. 2
- Not required
The opening is protected by a duct outlet penetration system that was tested with the rated assembly.
IBC 717.6.2 item 2 Exc. 3, IBC 717.6.2 item 3 Exc. 2
When a damper is not the answer
- Corridor damper rules do not apply
A corridor that is not required to be fire-resistance rated is not a fire partition, so the corridor damper rules do not apply to it.
Also required
- Flexible ducts and flexible air connectors may not pass through any fire-resistance-rated assembly, and flexible air connectors may not go through any wall, floor or ceiling at all. (ducts only) IBC 717.7
- Where no damper is required, the duct penetration must still be firestopped so the wall keeps its rating (through-penetration or membrane-penetration protection). IBC 717.1.2, IBC 714.3 to 714.4.3
- For a corridor ceiling under a rated floor: IBC 717.5.4.1 item 2 lists no exception. If the floor/ceiling or roof/ceiling assembly listing shows no ceiling radiation damper is needed, raise it with the building official. IBC 717.5.4.1 item 2
Common situations by edition
| Situation | 2024 IBC | 2021 IBC | 2018 IBC |
|---|---|---|---|
| Duct with a grille in the corridor, through a 1-hour corridor wall, building not sprinklered | Combination fire/smoke damper required | Combination fire/smoke damper required | Combination fire/smoke damper required |
| Same duct in a sprinklered building, firestopped as a through-penetration | Smoke damper required | Smoke damper required | Smoke damper required |
| Steel duct passing through the corridor with no openings in it, sprinklered building, firestopped | No damper required | No damper required | No damper required |
| Duct through a corridor ceiling built like the corridor walls | Corridor damper required | Corridor damper required | Corridor damper required |
| Duct to a corridor diffuser through the ceiling of a rated floor above, walls stopping at that ceiling | Smoke damper and ceiling radiation damper required | Smoke damper and ceiling radiation damper required | Smoke damper and ceiling radiation damper required |
| Duct through a corridor wall where the corridor is not required to be rated | Corridor damper rules do not apply | Corridor damper rules do not apply | Corridor damper rules do not apply |
Select a result to open it in the tool with every answer filled in, including the conditions not listed here.
Exceptions and conditions the tool checks
These are the questions the tool asks, in order, with the explanation it gives. Section numbers are shown for each edition where they differ.
Is the corridor required to be fire-resistance rated?
2018 IBC only
IBC Table 1020.1 sets corridor ratings by occupancy, occupant load and sprinklers. Many corridors in sprinklered buildings need no rating. A corridor wall can still be a fire partition for another reason, for example as a dwelling unit separation.
IBC Table 1020.1
2021 and 2024 IBC
IBC Table 1020.2 sets corridor ratings by occupancy, occupant load and sprinklers. Many corridors in sprinklered buildings need no rating. A corridor wall can still be a fire partition for another reason, for example as a dwelling unit separation.
IBC Table 1020.2
Where does the duct pass through the corridor enclosure?
- Through a corridor wall.
- Through a corridor ceiling built like the corridor walls. The corridor walls stop at the top of this ceiling, and the ceiling itself is rated like the walls (IBC 708.4 Exception 3).
- Through the corridor ceiling where the walls stop at the ceiling. The corridor walls stop at the lower membrane of the corridor ceiling, which matches the wall membrane (IBC 708.4 Exception 2).
- Through the ceiling where the corridor walls continue up to the floor or roof above. The corridor walls extend past the ceiling, so the ceiling is not part of the corridor enclosure.
IBC 708.4, IBC 717.5.4.1
Is either side of this wall a Group H (high-hazard) area?
Group H covers buildings or areas that store or use hazardous materials above set quantities.
What is the required fire-resistance rating of the assembly?
Use the rating the code requires for this wall or floor, shown on the life safety plans.
Is this a Group I-2 corridor (doors per IBC 407.3.1) or a multitheater corridor that meets IBC 716.2.2.1 Exception 3?
Doors in rated corridor walls must be smoke- and draft-control assemblies (IBC 716.2.2.1), which triggers the corridor smoke damper rule. Group I-2 corridor doors and certain multitheater corridors are the exceptions.
IBC 716.2.2.1, IBC 717.5.4.1 item 3
Does the building have an approved smoke control system throughout that does not depend on smoke dampers in the corridor?
IBC 717.5.4.1 Exc. 1, IBC 909
Is the duct steel at least 0.019 inch thick, with no openings serving the corridor?
A steel duct that only passes through the corridor, with no grilles or diffusers in it, does not need a smoke damper.
IBC 717.5.4.1 Exc. 2
Is the building fully protected by an automatic sprinkler system?
- Yes, NFPA 13 throughout. IBC 903.3.1.1
- Yes, NFPA 13R throughout. IBC 903.3.1.2, used in some residential buildings
- No, partial or NFPA 13D only.
Will the duct be protected as a through-penetration (IBC 714), either as tested in the rated wall design or with a listed firestop system having an F rating at least equal to the wall rating?
IBC 717.5.4 Exc. 1, IBC 714
Does the HVAC duct system meet all of these?
The exception applies only when every item is met:
- It is a ducted HVAC system carrying supply, return or exhaust air
- The ducts are sheet steel, No. 26 gage or thicker
- The steel ductwork is continuous from the air handling equipment to the air outlets and inlets
IBC 717.5.4 Exc. 4
Does the duct meet all of these?
This exception covers small steel ducts above a ceiling with a specific sleeve detail.
The exception applies only when every item is met:
- The duct is made of materials approved by the mechanical code
- The duct is no larger than 100 square inches
- The duct is steel at least 0.0217 inch thick
- The duct has no openings that connect the corridor with adjacent rooms or spaces
- The duct is installed above a ceiling
- The duct does not end at a wall register in the rated wall
- A steel sleeve at least 12 inches long and 0.060 inch thick is centered in the opening
- The sleeve is fastened on both sides of the wall and on all four sides of the sleeve with steel angles at least 1-1/2 by 1-1/2 by 0.060 inch, fastened to the sleeve and to the wall with No. 10 screws
- Mineral wool batting fills the gap between the sleeve and the wall all the way around
IBC 717.5.4 Exc. 3
Is the floor or roof above the corridor a fire-resistance-rated assembly that includes this ceiling?
IBC 708.4 Exception 2 lets the corridor walls stop at a corridor ceiling whose membrane is equivalent to the corridor wall membrane, either where the corridor wall’s room-side membrane continues up to the underside of a rated floor or roof above (Exception 2.1), or where the building is sprinklered throughout, including the space between the top of the wall and the floor or roof above (Exception 2.2).
IBC 708.4 Exc. 2
Is that ceiling the lower membrane of a rated floor/ceiling or roof/ceiling assembly?
If the ceiling is part of a rated floor or roof assembly, the penetration is regulated as a ceiling membrane penetration even though it is not part of the corridor enclosure.
IBC 717.6.2
Was the rated floor/ceiling or roof/ceiling assembly tested (ASTM E119 or UL 263) in a way that shows it keeps its rating without ceiling radiation dampers?
Some listed assemblies, such as certain UL designs, allow unprotected duct openings. Check the listing for the assembly.
IBC 717.6.2 Exc. 1
Is it an exhaust or outdoor air duct inside a wall cavity, protected as required by IBC 714.5.2, that does not run through any other dwelling unit or tenant space?
Typical case: a bathroom or dryer exhaust duct rising inside a wall and entering the rated ceiling at the top plate on its way outside.
IBC 717.6.2 Exc. 2
Is the duct protected with a duct outlet penetration system that was tested with the rated assembly (ASTM E119 or UL 263)?
This is a specific outlet or boot system named in the listing of the rated floor/ceiling or roof/ceiling design. A generic fire-rated boot or duct wrap does not count. Answer yes only if the assembly listing names the system.
IBC 717.6.2 Exceptions
Code changes that affect this assembly
- Ceiling radiation dampers: dynamic and static: Since 2021 separate sections cover dynamic and static ceiling radiation dampers, with control options for static ones.
- Static and dynamic fire dampers: Since 2021 the testing list no longer requires a dynamic label for fire dampers; a new section limits static-listed dampers to systems that shut down in a fire.
Questions
Where is a corridor damper required?
Where a duct passes through a corridor ceiling that is built like the corridor walls.
Corridor damper: requiredAll three editions
Corridor damper: required. The corridor ceiling is built like the corridor walls (IBC 708.4 Exception 3), so a corridor damper is required where the duct passes through it. Corridor dampers are tested for both fire and smoke. IBC 717.5.4.1 item 1, IBC 717.3.1 item 5
Full result in the tool: Corridor damper required
Does a duct through a corridor wall in a sprinklered building need a fire damper?
Not when the duct is protected as a through-penetration (not in Group H).
Fire damper: not requiredAll three editions
Fire damper: not required. In a fully sprinklered building, a duct through a corridor wall that is protected as a through-penetration does not need a fire damper. IBC 717.5.4 Exc. 1, IBC 714
Full result in the tool: Smoke damper required
When does a rated corridor need smoke dampers?
When the corridor must have smoke- and draft-control doors, unless an exception applies.
Smoke damper: requiredAll three editions
Smoke damper: required. The corridor requires smoke- and draft-control doors, so a listed smoke damper is required at each duct or air transfer opening through the corridor enclosure. IBC 717.5.4.1 item 3, IBC 716.2.2.1
Full result in the tool: Combination fire/smoke damper required
Do corridors that are not rated need dampers?
Corridor damper rules do not applyAll three editions
A corridor that is not required to be fire-resistance rated is not a fire partition, so the corridor damper rules do not apply to it.