IBC 717.5.2
Fire dampers in fire barriers (IBC 717.5.2)
A duct or air transfer opening through a fire barrier needs a fire damper unless one of three exceptions applies. Fire barriers need a smoke damper where they are also horizontal exits (IBC 717.5.2.1). If the same wall is also a smoke barrier or a corridor enclosure, those rules can add one too.
What counts as a fire barrier: Rated walls separating occupancies, fire areas, incidental uses, exit stairs, exit passageways or horizontal exits.
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
Ducts and air transfer openings through a fire barrier need a listed fire damper, and none of the exceptions apply.
IBC 717.5.2
- Alternative protectionDucts only
The duct is part of an approved smoke control system and a fire damper would interfere with it, so approved alternative protection is used instead of the damper.
IBC 717.5.2 Exc. 2, IBC 717.2.1
- Not required
The penetration was tested as part of the rated wall assembly.
IBC 717.5.2 Exc. 1
- Not requiredDucts only, 2021 and 2024 IBC
The fire barrier is rated 1 hour or less, the building is fully sprinklered, neither side is a Group H area, and the duct is a fully ducted steel HVAC system that is continuous from the equipment to the outlets.
IBC 717.5.2 Exc. 3
- Not requiredDucts only, 2018 IBC only
The fire barrier is rated 1 hour or less, the building is fully sprinklered, neither side is a Group H area, and the duct is a ducted steel HVAC system that is continuous from the equipment to the outlets.
IBC 717.5.2 Exc. 3
Smoke damper
- Required
The fire barrier serves as a horizontal exit, so a listed smoke damper is required.
IBC 717.5.2.1
- Not required
The fire barrier is not a horizontal exit.
IBC 717.5.2.1
When a damper is not the answer
- Not permitted
Ducts and air transfer openings may not penetrate the enclosure of an interior exit stairway, ramp or exit passageway unless the ductwork is dedicated to that enclosure. Dampers do not make a shared duct acceptable.
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
Common situations by edition
| Situation | 2024 IBC | 2021 IBC | 2018 IBC |
|---|---|---|---|
| Duct through a 2-hour fire barrier, no exception applies | Fire damper required | Fire damper required | Fire damper required |
| Duct through a 1-hour fire barrier, NFPA 13 sprinklers, fully ducted steel HVAC system | No damper required | No damper required | No damper required |
| Duct through a 1-hour fire barrier, steel ductwork not continuous to the outlets | Fire damper required | Fire damper required | Fire damper required |
| Air transfer opening through a 1-hour fire barrier | Fire damper required | Fire damper required | Fire damper required |
| Duct through a fire barrier that is also a horizontal exit | Combination fire/smoke damper required | Combination fire/smoke damper required | Combination fire/smoke damper required |
| Duct serving other spaces through an exit stair enclosure | Not permitted | Not permitted | Not permitted |
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.
Does the fire barrier enclose an interior exit stairway, exit ramp or exit passageway?
The walls around interior exit stairways, ramps and exit passageways are fire barriers with extra limits on what may pass through them. Exit access stairways enclosed as shafts are not covered by this question.
IBC 717.5.2, IBC 1023.5, IBC 1024.6
Does this wall serve as a horizontal exit?
A horizontal exit is a fire wall, fire barrier or horizontal assembly rated at least 2 hours, with doors, that lets people move to another building or a refuge area on the same level (IBC 1026). It is shown on the egress plans.
IBC 1026
Was this duct tested as part of the rated wall assembly itself (ASTM E119 or UL 263)?
Answer yes only if the fire-resistance design for this wall (for example a UL design) includes this penetration as tested. A listed firestop system tested to ASTM E814 or UL 1479 does not count.
Is the duct part of an approved smoke control system where a damper would interfere with how the system works?
Engineered smoke control systems (IBC 909) sometimes need ducts or openings to stay open during a fire. The smoke control design must show this.
IBC 909, IBC 717.2.1
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 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.
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.
Does the HVAC duct system meet all of these?
2018 IBC only
This exception lets ducts pass through low-rated fire barriers in sprinklered buildings without a damper, when the steel ductwork is continuous.
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 717.5.2 Exc. 3
2021 and 2024 IBC
This exception lets ducts pass through low-rated fire barriers in sprinklered buildings without a damper, when the steel ductwork is continuous.
The exception applies only when every item is met:
- It is a fully 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 (nonmetal flexible connectors are allowed only at the air handler in the mechanical room, and between an overhead metal duct and a ceiling diffuser in the same room)
IBC 717.5.2 Exc. 3
Is the duct part of an independent ventilation or pressurization system that serves only this exit enclosure?
Ductwork may enter an exit enclosure only when it is dedicated to that enclosure, such as stair pressurization. A system that also serves other spaces is not allowed, even with dampers.
IBC 1023.5, IBC 1024.6
Code changes that affect this assembly
- Fire barriers rated 1 hour or less: Since 2021 the exception says fully ducted and expressly allows nonmetal flexible air connectors at the air handler connection and between an overhead metal duct and a ceiling diffuser in the same room. The similar fire partition exception (717.5.4 Exc. 4) did not change.
- Ducts in exit passageways: Since 2021 ductwork for independent ventilation, not only pressurization, may penetrate an exit passageway.
- 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
Does every duct through a fire barrier need a fire damper?
No. The fire damper is dropped where the penetration was tested as part of the wall design or where the 1-hour exception for fully ducted HVAC systems applies, and approved alternative protection replaces it where it would interfere with a smoke control system.
Fire damper: requiredAll three editions
Fire damper: required. Ducts and air transfer openings through a fire barrier need a listed fire damper, and none of the exceptions apply. IBC 717.5.2
Full result in the tool: Fire damper required
Do fire barriers need smoke dampers?
Under the fire barrier rules, only where the fire barrier also serves as a horizontal exit. A wall that is also a smoke barrier or a corridor enclosure can need one under those rules.
Smoke damper: requiredAll three editions
Smoke damper: required. The fire barrier serves as a horizontal exit, so a listed smoke damper is required. IBC 717.5.2.1
Full result in the tool: Combination fire/smoke damper required
What is the 1-hour fire barrier exception?
It removes the fire damper for fully ducted steel HVAC systems in sprinklered buildings where the fire barrier is rated 1 hour or less.
Fire damper: not required2021 and 2024 IBC
Fire damper: not required. The fire barrier is rated 1 hour or less, the building is fully sprinklered, neither side is a Group H area, and the duct is a fully ducted steel HVAC system that is continuous from the equipment to the outlets. IBC 717.5.2 Exc. 3
Also: 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
Full result in the tool: No damper required
Fire damper: not required2018 IBC only
Fire damper: not required. The fire barrier is rated 1 hour or less, the building is fully sprinklered, neither side is a Group H area, and the duct is a ducted steel HVAC system that is continuous from the equipment to the outlets. IBC 717.5.2 Exc. 3
Also: 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
Full result in the tool: No damper required
Can a duct pass through an exit stair enclosure?
Only ductwork dedicated to that enclosure, such as stair pressurization.
Not permittedAll three editions
Ducts and air transfer openings may not penetrate the enclosure of an interior exit stairway, ramp or exit passageway unless the ductwork is dedicated to that enclosure. Dampers do not make a shared duct acceptable.